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The Effects of Nutritional Yeast for Cancer 

Tue, 09/14/2021 - 07:00

How can the beta glucan fiber in brewer’s, baker’s, and nutritional yeast improve wound healing and, potentially, anti-cancer immunity? 

My video Benefits of Nutritional Yeast for Cancer opens with an image of an article titled “The Treatment of Inoperable Cancer.” It noted that “200 years ago it was observed that a certain number of malignant growths disappeared after an attack of erysipelas [a type of strep infection]”—and that was 200 years before 1901, when the article was published in The Medical Press. A disproportionate number of cases of “spontaneous tumour regression” have followed various infections. The thought is that an infection may rile up the immune system so much that the cancer may get caught in the cross-fire. This phenomenon may have even inspired healers dating back to the ancient Egyptians, thousands of years ago. But, you (or the ancient Egyptians) don’t know until you put it to test. 

It wasn’t formally studied, however, until the 1800s, when doctors began intentionally infecting cancer patients. The most famous proponent was William Coley, known as the “Father of Immunotherapy” at what would eventually become Memorial Sloan Kettering. “Coley was convinced that having a severe infection could cause cancer to regress. It took a great deal of courage, but in 1891 he injected his first [cancer] patient with streptococcal organisms and noticed the shrinkage of a malignant tumor.” The problem, of course, is that causing infections is quite dangerous. Two of his patients died of infection, but their tumors did shrink. If only we could boost the immune system without killing the patient. 

In fact, that’s the theory behind therapeutic cancer vaccines. One such treatment that has been in practice for decades involves squirting a weakened bovine tuberculosis bacteria into the bladders of patients with bladder cancer to make the immune system attack, boosting long-term survival up to 36 percent, as you can see at 1:56 in my video. Rather than getting urethral squirts of a cow’s TB bacteria, is there something we can eat that can boost our immune function? In my videos on countering stress-induced immune suppression and preventing common childhood infections, I reviewed evidence about beta-glucans, a type of fiber found in baker’s, brewer’s, and nutritional yeasts. “Yeast-derived beta-glucans…are considered immunomodulatory compounds suggested to enhance the defense against infections and exert anticarcinogenic effects”—that is, potentially fight cancer. 

Beta-glucans themselves do not appear to have a direct cytotoxic effect in terms of killing cancer cells, but they may boost anti-tumor immunity by activating our immune cells, as you can see at 2:32 in my video. If you take freshly excised tumors of breast cancer patients, for example, and let natural killer cells loose on them, they can kill off a small percentage of the tumor cells. But, if you first prime the NK cells in vitro with some yeast beta-glucans, they become about five times more effective at killing cancer cells, as you can see at 2:43 in my video. What if you just eat the beta-glucans, though? 

When 23 women with metastatic breast cancer were given the beta-glucans in just 1/16th of a teaspoon of nutritional yeast, they experienced a 50 percent increase in the number of monocyte white blood cells (part of our natural defenses) in their bloodstream and a significant increase in their activation. The study only lasted two weeks, though, and the clinical significance of this finding is unclear. What we want to know is whether they actually live longer. 

The only English-language randomized, double-blind, placebo-controlled trial of breast cancer patients and beta-glucans was actually more of a wound–healing study. Researchers found that women taking beta-glucans healed so much faster after mastectomy surgery that the drain discharge tubes could be removed from their chests and armpits days earlier in some cases. This was the first clinical study to demonstrate improved wound healing using oral beta-glucans. Two other studies that showed benefits—one studying pediatric burns and another examining leg ulcers—were performed using topical beta-glucan preparations that were put directly on the skin. Topical application did not appear to reverse pre-cancerous skin lesions better than placebo, as you can see at 4:15 in my video, but that’s because the placebo cream also worked well. Indeed, both groups showed a significant reduction. But, each patient in the study “acted as their own control,” meaning they put the beta-glucan cream on one of their arms and the placebo cream on the other. The researchers speculated that the beta-glucans applied to one arm may have been absorbed into the system and helped the other arm. Systematic effects following topical administration had been noted previously.  

What effect might oral beta-glucans have on the progression of internal cancers? Yes, oral yeast beta-glucans can cause dramatic tumor shrinkage—in mice. What about in people? There appears to be only one human study published in English. As you can see at 5:01 in my video, 20 patients with advanced cancer on chemotherapy were given a beta–glucan supplement in an open–label, uncontrolled trial. “Sixty per cent of the patients reported a sense of well-being while taking the [beta]-glucan and asked to remain on the treatment even after the completion of the study. Forty per cent of the patients…reported feeling less fatigued while taking the [beta]-glucan.” But, those results sound like classic placebo effect. There was something of interest, though: “One patient with lymphoma and significant cervical adenopathy [enlarged lymph nodes in the neck] who delayed his standard chemotherapy for 4 weeks during the study…noted a marked reduction in the size of the nodes while taking the [beta]-glucan alone.” Although this one anecdotal case is intriguing, especially since there are no side effects, it isn’t exactly revolutionary. 

In Japan, there have been 22 randomized controlled studies on the use of beta-glucans as an adjunct cancer treatment. Researchers found that “yeast [beta]-glucan…can enhance the effect of anticancer chemotherapy or radiation therapy and have a positive effect on the survival and quality of life of cancer patients.” One study, for example, examined taking a yeast beta-glucan supplement to help prevent cancer relapse after surgery. The treated group did not have any relapses, compared to about one in five in the control group. Even more intriguing was the impact of yeast beta-glucans for patients with inoperable, end-stage cancer. In the control group, only about 1 in 20 patients survived for three months, and, by six months, everyone had died. In the treated group, however, most of the patients survived for more than three months—not just 1 in 20, but most—and 43 percent were still alive after six months. It’s not clear, though, how patients were divvied up into the treatment and control groups. If the subjects weren’t randomly assigned, the researchers may have inadvertently cherry-picked healthier patients for the treatment group, which could explain the results.  Regardless, the amount of beta-glucans they used is what you’d find in a single pinch of nutritional yeast, which would cost less than a penny, and the only side effect would be tastier popcorn. So, why not give it a try? 


  • Researchers have found that beta-glucan fiber in brewer’s, baker’s, and nutritional yeasts may “enhance the effect of anticancer chemotherapy or radiation therapy and have a positive effect on the survival and quality of life of cancer patients.” 
  • Yeast beta-glucans have been shown to help prevent cancer relapse after surgery and may extend survival for those with inoperable, end-stage cancer. 
  • Oral beta-glucans have also been shown to improve wound healing in breast cancer patients after mastectomy surgery, and topical beta-glucan preparations were found to have benefits on pediatric burns and leg ulcers.
  • Though they do not directly kill cancer cells, beta-glucans may boost anti-tumor immunity by activating our immune cells.

If beta glucans are really so powerful, might there be concern that they might overstimulate the immune system in certain autoimmune conditions? Yes. See Does Nutritional Yeast Trigger Crohn’s Disease? and Is Nutritional Yeast Healthy for Everyone? for more information. 

What about beta glucan fiber for fighting off run–of–the–mill infections? Check out: 

In health, 

Michael Greger, M.D. 

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations: 

Does Coconut Oil Help with Abdominal Fat?

Thu, 09/09/2021 - 07:00

What does a review of the evidence on the effects of coconut oil on weight loss and belly fat find? 

I begin my video Flashback Friday: Coconut Oil and Abdominal Fat with a popular infographic that surprised me by showing that, evidently, there is promising evidence that coconut oil could help with obesity. Well, if you fill the stomachs of rats with purified medium-chain fatty acids, one component of coconut oil, they end up eating less food, as you can see at 0:25 in my video, but you don’t know if there’s any relevance to humans until you put it to the test.  

Researchers compared breakfasts with the same amount of dairy fat, coconut oil fat, or tallow (beef fat), and there was no effect on hunger, fullness, satisfaction, or how much the subjects then went on to eat at lunchtime. Where did this idea that coconut fat is somehow different from other kinds of fat come from? Six years ago, an open-label pilot study was published. Researchers asked 20 men and women to eat two tablespoons of coconut oil each day for a month. As you can see at 1:03 in my video, the men appeared to lose about an inch off their waist. But, since it was an open-label study, the participants knew what they were eating. There wasn’t a placebo control. In fact, there was no control group at all. Because of that, we can’t know if the effects would have happened anyway, even without the coconut oil. Indeed, there is a well-recognized effect in dietary studies where just being in a dietary study under observation tends to lead to a reduction in caloric intake, because the subjects know they’re going to be weighed and observed.  

We finally got a controlled study of coconut oil and waistlines in men and women in 2015. About a hundred men and women were given about a tablespoon of coconut oil a day for three months and, as you can see at 1:51 in my videolost nearly an inch off their waist compared to control by the end of the study. What did the control group get instead of coconut oil? Nothing. There was no placebo, so the researchers compared doing something with doing nothing. When one does that, however, there is often a placebo effect regardless of the true efficacy of the treatment. What’s more, the researchers suggested that the coconut oil group may want to take their daily dose with fruit. If the subjects did end up eating more fruit, that in itself may have helped with weight reduction because, despite its sugar content, fruit consumption tends to be associated with “anti-obesity effects.”  

What we need to determine if coconut oil has some type of special effect is to give people a spoonful of coconut oil versus a spoonful of another oil and see if there’s any difference. When researchers did just that—giving subjects either two daily tablespoons of coconut oil or soybean oil—there was no significant difference in waistlines. But, the coconut oil group got a significant increase in insulin resistance, which is what eventually causes type 2 diabetes, and this was despite receiving instruction to increase fruit and vegetable consumption and cut down on sugars and animal fat, and engaging in an exercise program of walking 50 minutes a day, four days a week.  

The only other placebo-controlled study of coconut oil and waistlines was published in 2017, and, as you can see at 3:18 in my video, the researchers found no significant changes in weight, waist or hip measurements, total fat, belly fat, or butt fat. No benefit to coconut oil for obesity over placebo has been found in any study to date. How then can coconut oil proponents get away with saying otherwise? They like to talk about studies such as the one showing that Pacific Islanders who ate more traditional coconut-based diets are slimmer than those eating more modern diets with fewer coconut products. Okay, but what were those on the “modern dietary pattern” eating instead? “The modern dietary pattern [was] primarily characterized by high intake of sausage and eggs, and processed foods…” 


  • When researchers compared morning meals with equal amounts of fat from dairy, coconut oil, and tallow (beef), no effect was found on hunger, fullness, satisfaction, or the amount then eaten during lunch.  
  • The idea that coconut fat is unique to other fats appears to have come from an open-label study without a placebo or any control group at all, and, since the subjects knew what they were eating, we cannot know what effect, if any, the coconut fat may have.
  • A controlled study of coconut oil and waistlines was also unsatisfying in that the control group didn’t get a placebo, so the researchers compared doing something to doing nothing, which can result in a placebo effect. Additionally, those in the coconut oil group were told they may take their daily dose with fruit, and increased fruit intake may itself help with weight reduction.
  • Finally, a study was conducted in which subjects were given two daily tablespoons of either coconut oil or soybean oil, and no significant difference in waistlines was found. The coconut oil group did, however, get significant increases in insulin resistance, which may cause type 2 diabetes. 
  • To date, no benefit to coconut oil for obesity over placebo has been found. 

Have you heard there is something special about those medium–chain fatty acids? Check out What About Coconuts, Coconut Milk, and Coconut Oil MCTs? for more. 

And a bump in good cholesterol? I’ve got a video on that too. See Coconut Oil and the Boost in HDL “Good” Cholesterol

My other videos on coconut oil include: 

What can really help with weight loss? Of my dozens of videos on the topic, Eating More to Weigh Less and Paleopoo: What We Can Learn from Fossilized Feces are good places to start. 

In health, 

Michael Greger, M.D. 

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations: 

Countering Stress-Induced Immune Suppression with Diet

Tue, 09/07/2021 - 07:00

How might we improve immune function in children and adults under physical or psychological stress? 

Natural immunomodulators”—compounds that might regulate our immune systems naturally—”are getting more and more popular. The popularity, however, often brings over-optimistic claims and mediocre effects.” Such mythical beasts have been sought after for centuries. The current market is full of all sorts of supplements “promising the golden fleece”—inexpensive and without side effects, yet actively boosting our immune systems. “Many are simply repeating claims with hardly any substantial scientific background” to support them. On the other hand, there’s beta-glucan, which has undergone more than 10,000 scientific studies and clinical trials. Wait, what? If you remember, beta-glucan is the fiber in nutritional yeast I talked about previously in my video Preserving Immune Function in Athletes with Nutritional Yeast, and it is able to decrease episodes of common illnesses in young children. What about in adults? 

But, first, why can’t researchers just come up with a vaccine against the common cold virus? Because there is no single common cold virus. Hundreds of different viruses are implicated in causing cold-like symptoms, which is why there is so much interest in finding a general, nonspecific immune booster that works across the board, as I discuss in my video Flashback Friday: Best Food to Counter Stress-Induced Immune Suppression

Immunoglobulin A (IgA) is an antibody that plays a crucial role in the immune function of our moist membranes, such as our eyes, nose, and mouth. As you can see at 1:27 in my video, beta-glucan supplementation can increase IgA levels in the saliva within four days at a daily dose of 400mg, but not at 100mg. So, the effective amount is found in about two daily teaspoons of nutritional yeast, but a half teaspoon is ineffective. A single teaspoon’s worth didn’t do much until research participants exercised. As you can see at 1:48 in my video, two hours after a 50–minute bout of strenuous cycling in a hot, humid environment, those who had been on the yeast beta-glucan did get that IgA boost. However, beta-glucans failed to boost the antimicrobial activity of white blood cells of subjects who had been taking about a tablespoon’s worth a day, as you can see at 2:06 in my video. What we care about, though, are clinical outcomes. Do those consuming beta-glucans suffer significantly fewer infections? 

How about a double-blind, randomized, placebo-controlled nutritional study to see if yeast beta-glucan can improve our immune defense system? Sounds good! One hundred people were followed for 26 weeks. Fifty subjects got about a tablespoon of nutritional yeast’s worth of beta-glucan a day, and the other half got a placebo. Participants counted how many episodes of the common cold they got, and there was no significant difference. If you look only at the first half of the study duration, during cold season, there did appear to be fewer infections in the beta-glucan group, but going back and looking at your data after the fact is what’s called a post-hoc analysis, which is frowned upon by the scientific community because it increases the likelihood that your findings are due to chance. However, those who did end up getting sick while on the beta-glucan did genuinely appear to suffer milder symptoms, as you can see at 3:09 in my video. A similar, larger study had similar findings. The severity of the colds may have lessened, but, in the main analysis, there was no significant difference in the number of times people got colds in the first place. 

Indeed, “no significant differences between the treatment and placebo groups in the number of SRI [symptomatic respiratory infection] episodes” were seen in other studies, and there was no significant effect on upper respiratory tract infection outcomes either. So, overall, the results were pretty disappointing. 

But, wait a second. What about my previous video that I mentioned at the start of this article? The one about preserving immune function in athletes with nutritional yeast. In that video, I had discussed how researchers had found a significant drop in cold symptoms at two weeks and at four weeks after a marathon at doses of one teaspoon of yeast’s worth of beta-glucan a day and also at two teaspoons’ worth. Okay, the subjects had just run a marathon, though…but, wait. Remember the study where the effect only seemed to emerge after strenuous exercise? That’s where beta-glucan seems to shine: counteracting the toll that extreme physical exertion can have on our immune function. 

In an athlete, that may just mean some lost training or practice days, but for soldiers or firefighters, for example, maintaining one’s health—even in the context of heavy physical stress—could be critical. Yes, but that’s counteracting the effects of physical stress. What about mental stress? 

Stressful life events can impair our moist membrane defenses, such that “psychological stress [has] been shown to increase susceptibility to the common cold and increased upper respiratory tract infection (URTI) episodes.” So we’re talking stressed-out people getting more colds and worse colds than people under less stress. Can beta-glucan help in any way? Indeed, in a study of healthy women under “moderate levels of psychological stress,” those taking about a teaspoon of nutritional yeast’s worth of beta-glucans every day for 12 weeks were 60 percent less likely to report experiencing symptoms like a sore throat, stuffy or runny nose, or cough. “This strongly suggests that…yeast beta-glucan is able to counteract the negative effects of stress on the immune system,” and, as you can see at 5:24 in my video, the subjects on beta-glucan experienced 41 percent greater vigor, which is a measure that encompasses “physical energy, mental acuity, and emotional well-being.” So, they just felt better, too. 

When we put all the studies together, yeast beta-glucans do appear to have “an immune strengthening effect,” at least in children and those under physical or mental stress. 


  • Beta-glucan, the fiber in nutritional yeast, is able to decrease episodes of common illnesses in young children.
  • The antibody immunoglobulin A (IgA) is important for our moist membranes, including our eyes, nose, and mouth. 
  • About two daily teaspoons of nutritional yeast can increase IgA levels in saliva within four days.
  • Yeast beta-glucan intake may improve our immune defense system, able to reduce the severity of colds.
  • Two and four weeks after subjects ran a marathon, researchers found significant drops in cold symptoms at doses of one and two teaspoons of yeast’s worth of beta-glucan a day.
  • Beta-glucan seems to excel at counteracting extreme physical exertion and psychological stress.
  • Overall, yeast beta-glucans appear to have “an immune strengthening effect” in children and those under physical or mental stress. 

Best Food to Prevent Common Childhood Infections is the video I produced about child immune function. What about the Benefits of Nutritional Yeast for Cancer? 

Some people probably should not eat nutritional yeast, though. See:  

To learn more about foods that may help support optimal immune function, see: 

 In health, 

Michael Greger, M.D. 

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations: 

How to Become a Soy Equol Producer 

Thu, 09/02/2021 - 07:00

Certain gut bacteria can supercharge the benefits of soy foods, resulting in even more bone protection, better control of menopausal symptoms, and lower prostate cancer risk, but how can we foster the growth of these good bacteria? 

“Menopause is characterized by a decrease in estrogen, which triggers the uncomfortable symptoms of hot flushes [also known as hot flashes], night sweats, sleep disturbances, and vaginal dryness. Among these menopausal symptoms, hot flushes are reported by many women to be the most bothersome.” You may be familiar with my summary of the available evidence on the role of soy phytoestrogens to help alleviate those symptoms presented in my earlier video Soy Foods and Menopause. I discuss the latest meta-analysis in my more recent video, How to Convert Into an Equol Producer. Although the balance of evidence points to the benefits of soy, the individual study results are all over the place. Yes, some studies show 20, 30, even 40 percent better than control, but some showed no effect, as you can see at 0:38 in my video

This is something that’s been noted by professional societies like the American College of Obstetricians and Gynecologists. Indeed, these supplements may work, but the evidence is inconsistent. This may be partly because the supplements used were extracted from different parts of the soybean. It might be better if, instead of supplements, soy foods were used. The dosing would be about two servings of traditional soy foods a day—for example, two cups of soy milk. In fact, that is what you see older women in Japan doing, and they have some of the lowest reported rates of hot flashes in the world. Nevertheless, even the studies on soy foods, as opposed to supplements, have reported “conflicting results.” Why all the inconsistency? It may have to do with our gut bacteria. 

People who eat foods made from soybeans, which have “health-promoting isoflavones,” tend to have lower rates of a variety of chronic diseases, such as “cardiovascular disease, osteoporosis, and some cancers such as breast, prostate, and colon cancers,” so can we garner this protection by eating more soy foods? It may be a little more complicated than that. There are certain gut bacteria that can convert isoflavones in soy into a potentially even more beneficial compound called equol, but not all individuals can make this conversion. Why not? Because not all individuals have the specific types of good bacteria in their gut that do it. There are two types of people in the world: equol producers and equol nonproducers, depending on their gut flora. This may help account for the variations in health benefits we see in clinical studies; it may help explain why some people seem to benefit from soy more than others.  

For example, you may remember a study I covered previously about how soymilk appears to prevent bone loss in the spines of postmenopausal women, which I show at 2:32 in my video. Well, if you split those women into equol producers and equol nonproducers, you’ll find that soy did work in equol nonproducers, but it seemed to work even better in the women whose gut bacteria can take the soy to the next level. 

The more equol Japanese women make from the soy they eat, the fewer menopausal symptoms they may have, as you can see at 2:55 in my video. Some studies suggest equol-producing men may get less prostate cancer. If that’s the case, perhaps we should “examine the possibility of improving the intestinal environment to enable equol production.” Only a minority of the Western adult population can produce equol, though nearly every other animal species appears to be able to produce it without any problem. In fact, it got its name because it was first discovered in equines. Interestingly, horses produce equol during the summer, but not the winter, because summertime is when their gut bacteria have access to the phytoestrogens in clover. That was our first clue that equol was made from plants. 

“This then begs the important question, i.e., can we take someone who does not make equol and convert them to an equol–producer? Certainly, it is possible to do the reverse; excessive use of antibiotics, which wipe out intestinal flora, is likely to do this” by getting rid of your good bugs, but how can you acquire the right good bugs? Suggested strategies include dietary alteration or probiotics.  

The standard probiotic regimens don’t seem to help, though, so how about dietary alteration? About half of Japanese and Korean individuals can produce equol, but only as low as one in seven Americans can. Could it be because more soy is eaten in Asia? That would make sense: If you eat a lot of soy, you may foster the growth of bacteria in your gut that can digest soy. A month of soy isoflavone supplement exposure didn’t seem to convert equol-nonproducers into producers, though. After just two weeks of drinking three glasses of soy milk a day, however, three of six women were converted into equol-producers. As you can see at 4:45 in my video, for example, a woman started out hardly making any equol at all. After two weeks of drinking soy milk, though, she got nice equol spikes when the researchers had her drink some more, but it didn’t work for all women. And, when researchers tried the same experiment in men, nothing happened. Back to the drawing board. 

Is there any group of Westerners with high equol production rates from whom we may be able to get a clue? Vegetarians have among the highest equol production rates ever recorded and are more than four times as likely to be equol producers as their non-vegetarian counterparts. Why? Researchers don’t think it’s because of the soy, given the conflicting soy data, but could it be because they’re eating more prebiotics, such as fiber? Or, maybe dietary fat intake decreases the capacity of gut flora to make equol, or perhaps it has something to do with cholesterol intake. Analyzing the diets of equol producers, it seems they are more likely to be eating greater amounts of carbohydrates, plant protein, and fiber. 

Researchers have tried giving people fiber supplements along with soy, but that didn’t seem to work. Whatever it is about those eating plant-based diets, they may soon be the only remaining majority equol producers as Asian populations continue to Westernize their diets. 


  • The balance of evidence finds that soy is beneficial for alleviating menopausal symptoms.
  • Eating foods made from soybeans may lower rates of myriad chronic diseases, including heart disease, osteoporosis, and breast, prostate, and colon cancers.
  • Certain gut bacteria can convert the isoflavones in soy into equol, which is potentially even more beneficial, but not everyone has the specific types of bacteria to do so.
  • This difference in gut flora may help explain the variations in soy benefits found in studies.
  • Those whose gut bacteria are able to produce equol may experience fewer menopausal symptoms and less prostate cancer, for example.
  • Only a minority of Western adults can produce equol, though virtually all other animal species seem to be able to do so. 
  • Equol is made from plants. 
  • Vegetarians have among the highest rates of equol production and are more than four times as likely to produce equol than non-vegetarians.

What was that about safely helping to control hot flashes? Check out my video Soy Phytoestrogens for Menopause Hot Flashes

Plant-based eating has a variety of healthy effects on our good gut bacteria. See, for example: 

In health, 

Michael Greger, M.D. 

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations: 

How Much Lead Leaches Into Organic Chicken Bone Broth?

Tue, 08/31/2021 - 07:00

“Lead poisoning still occurs in the United States despite extensive prevention efforts and strict regulations.” Ayurvedic supplements specifically marketed to pregnant women, for example, exceeded safety levels by up to 4 million percent, making Ayurvedic medicine use and lead poisoning “a continued concern in the United States.” In fact, “heavy metals are added intentionally to several Ayurvedic medications,” though Ayurvedic practitioners claim that practice shouldn’t cause worry because the “process of detoxifying heavy metals…includes the use of…cow’s urine” among other substances.

We’ve known for about a half-century now that calcium supplements can be an additional source of lead contamination. Those made from bone may have the highest lead levels, but regular calcium supplements, including a number manufactured by national brands, were also found to be contaminated.

In terms of our diet, the greatest contributor to the lead intake of children and their parents may be dairy, but the most concentrated source may be wild game shot with lead-containing ammunition. Concerns have been raised by hunters, though, that lead-free bullets wouldn’t have the same “wounding capacity.” However, CT scans of kills show they inflict just as much damage, “demonstrat[ing] that lead-free bullets are equal to conventional hunting bullets in terms of killing effectiveness,” even against ballistic soap, which evidently has a similar density to vital organs.

Workers in battery plants, for instance, can be exposed to a lot of lead, but the number one nonoccupational exposure is from shooting firearms. It isn’t eating lead-laden meat—just taking target practice in indoor firing ranges. Indeed, 75 percent of target shooters have elevated lead levels in their blood, as you can see at 2:02 in my video How Much Lead Is in Organic Chicken Soup (Bone Broth)?. Even outdoors, airborne lead released by the friction of the bullet against the barrel or lead-containing primers can cause substantial lead exposure both in people and local wildlife, as well as contaminate the soil. Lead levels in the soil by a firing range were higher than those found next to an industrial lead factory. However, most lead in urban soil is from decades of use of leaded paint and gasoline, raising concerns about urban gardens. Though most of the lead in soil doesn’t get taken up by plants, it can stick to their leaves and roots. This is bad news since even crops from raised beds using clean soil may get contaminated in an urban environment, but, the good news is that, presumably, the lead can just be washed off. The health benefits of gardening and fresh produce “are likely to more than fully compensate risks at most sites.”

What about eggs from backyard chickens? They should be tested for lead because the lead gets inside the eggs and therefore can’t be washed off. As you can see at 3:22 in my video, most of the lead ends up in the birds’ skeletons, which raises the question: What happens when you try to make chicken soup?

There may be an upswing in people boiling bones, which is “encouraged by advocates of the paleolithic (or ‘paleo’) diet,” but the problem is that lead is a neurotoxin—but not just a neurotoxin. Lead also adversely affects the bone marrow, digestive tract, kidneys, circulatory system, hormones, and reproduction. Symptoms of too much lead exposure include impaired cognition, anemia, abdominal pain, kidney problems, high blood pressure, miscarriages, memory problems, constipation, impotence, depression, poor concentration, and more. What’s more, we know from human studies that lead is sequestered in bones. When there is a lot of bone turnover, for example, during menopause or pregnancy, lead levels in the blood can go up. This bump can be minimized during pregnancy by getting enough calcium and lowering sodium intake, though. When astronauts lose bone in space, the lead is released into their bloodstream. Ironically, since they’re no longer being exposed to all the lead on Earth, their overall lead levels may go down. Bones are so good at sucking up lead, they can be sprinkled on firing ranges to prevent lead from leeching further into the environment.

Researchers concerned that the boiling of farm animals’ bones might release lead into the broth made three types of organic chicken broth—one using the bones, a second using meat without the bones, and a third using the skin and cartilage without the bones. All three of the broths exceeded the maximum allowable dose level for lead—even the one made without bones. Surprisingly, the skin and cartilage broth was the worst, exceeding the safety level per one-cup serving by about 475 percent.


  • Leading poisoning is a concern in Ayurvedic medicine and calcium supplements, not only those made from bone.
  • Dairy may contribute most to our intake of lead dietarily, but wild game shot with lead-contaminating ammunition may be the most concentrated source.
  • Shooting firearms, including at target practice in indoor ranges, is the top nonoccupational exposure to lead.
  • Airborne lead released from shooting can expose people and wildlife, as well as contaminate the soil, and levels in the ground by a firing range have been found to be higher than those next to an industrial lead factory. 
  • In urban soil, most lead is from decades of use of leaded paint and gasoline.
  • Eggs from backyard chickens should be tested for lead as it may get inside the eggs and cannot be rinsed off.
  • Lead is sequestered in bones, and boiling the bones of farm animals may release lead into the broth. 
  • Lead exceeding the maximum allowable dose level was found in broths made from organic chicken bones, organic chicken meat without the bones, and organic chicken skin and cartilage without the bones.

Did you just experience a little déjà vu? About two years ago, I produced a video about this very same study. Then, while researching for my extensive series on lead last year, I ran across the paper again and created the video for this article. Once I realized I had double-dipped on the same study, I had fun going back to see how such a different video can be produced around the same science. You can check out the first video at Lead Contamination in Bone Broth.

I alluded to my videos California Children Are Contaminated and Filled Full of Lead. For even more on lead, see:

Interested in the paleo diet? Here’s the science I could find on it:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations:

Summer Sale – 20% Off Everything

Thu, 08/26/2021 - 07:00

All digital downloads, shirts, and outreach material on are 20 percent off until tomorrow, August 27! Proceeds go to support

We are thrilled to debut our new diversity shirt! We have long stressed the importance of dietary diversity. Each plant family has a unique combination of phytonutrients, which is one of the reasons I developed the Daily Dozen to encourage eating a variety of the very best foods each day for health and longevity. We also continue to share life-saving, life-changing science-based information to communities around the world, which is why everything on our website is free and all of our videos are translated into multiple languages. We’re thankful we get to take part in helping to make the world a more healthful place for everyone. All of the proceeds from the sale of our new diversity shirt will support Food Empowerment Project, a nonprofit food justice organization.

Get your shirt here.


Volume 55 Out Now

My new volume of videos is out today and covers mushrooms, mycotoxins, fasting, bariatric surgery, and more. It is available as a streaming video so you can start watching it immediately. Each video in this new collection will be released online over the next few months, all available for free, of course, but if you don’t want to wait, you can watch all of them by streaming right now

And, remember, if you watch the videos on or YouTube, you can access captions in several different languages. To find yours, click on the settings wheel in the lower-right of the video and then “Subtitles/CC.” Happy viewing!

If you are a $25+ monthly supporter and opted in to our donor rewards, you’d be an expert on these new topics by now, having already received a complimentary link to the new download. If you’d like to receive them before they’re available to the public, please consider becoming a monthly supporter.

Sign up on the donation page to become a $25+ monthly contributor, and be given an opportunity to receive early access to the newest downloads for free as long as your contributions are current. We’re so appreciative of each one of our donors. Without your support, we wouldn’t be able to continue our work. 


Key Takeaways: Flaxseeds

I include a tablespoon of flaxseeds in my Daily Dozen checklist of the healthiest foods to eat each day. They’re a rich source of omega-3 fatty acids and cancer-fighting lignans. 

Read more on our topic page, and check out videos like Benefits of Flaxseed Meal for Weight Loss and Flax Seeds vs. Diabetes.

Recipe: Buffalo Cauliflower with Ranch Dressing

Looking for a delicious way to snack on some crucifers? Get the free recipe here, originally published in my How Not to Die Cookbook, and watch how it’s made on our Instagram.  





Outreach Cards in English and Spanish

Our outreach cards make it easy to tell your friends, colleagues, and family—or strangers!—about I’m happy to announce they are now also available in Spanish. (At this point, shipping is only available in the United States.)

Get your cards here: English | Spanish

        Volunteer Spotlight: María Belén Oliva

“I’ve been volunteering as a translator/subtitler at NutritionFacts for some months now and I couldn’t be happier. I’m driven by my passion for food and wellbeing, and to be able to help spread such important content around the world with my translations is really inspiring!

It’s difficult to pick a favourite recipe, but I think it could be an Armenian salad with roasted eggplants, bell peppers, chestnuts, and raisins.”




The Benefits of Moringa: Is It the Most Nutritious Food? 

Does the so-called miracle tree live up to the hype?


200-Pound Weight Loss Without Hunger 

I dive into one of the most fascinating series of studies I’ve ever come across.


Is It Safe to Eat Raw Mushrooms? 

Microwaving is probably the most efficient way to reduce agaritine levels in fresh mushrooms.



Live Q&A on September 23 


Every other month, I do a Q&A live from my treadmill, and September 23 is the next one.

Join on our Facebook page or YouTube channel at 3pm EDT. I’ll be streaming to both at the same time!

You can find links to past live Q&As here on If that’s not enough, remember, I have an audio podcast to keep you company, too.


In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:

Soy Phytoestrogens for Menopausal Symptoms

Tue, 08/24/2021 - 07:00

Does soy food consumption explain why Japanese women appear to be so protected from hot flash symptoms?

When women hit menopause and their ovaries shut down, the estrogen level in their body drops 95 percent. This is good news for the endometrium, the lining of the uterus. Otherwise, the constant estrogen signaling could eventually result in endometrial cancer. In fact, that may be why menopause evolved: to protect the uterus from cancer. Lower estrogen levels are also beneficial for lowering breast cancer risk. In postmenopausal women, relatively high blood levels of estrogen are associated with a more than double increased risk for breast cancer. But why do estrogen levels drop 95 percent at menopause, but not all the way down to zero? Because estrogen can be made by other tissues, like our own fat cells, and “this probably explains the increase in [breast cancer] risk in obese postmenopausal women.” More fatty tissue means more estrogen production. 

In my earlier video How to Block Breast Cancer’s Estrogen-Producing Enzymes, I discussed how soy phytoestrogens can block the production of estrogen, such that drinking a glass of soy milk with each meal can cut estrogen levels in half in premenopausal women. But estrogen levels in postmenopausal women are already down 95 percent, and, because of that, many women, approximately 8 in 10, suffer from hot flashes. Might lowering levels even further with soy make menopausal symptoms even worse? That’s the subject of my video Soy Phytoestrogens for Menopause Hot Flashes

Estrogen treatment reduces menopausal symptoms very effectively, but, unfortunately, its downsides include not only the uterine cancer, but blood clots, strokes, and cognitive impairment, as well. Taking progesterone-type compounds with the estrogen prevents uterine cancer, but increases the risk of heart attacks, more stroke, breast cancer, more clots, and dementia. What’s a woman to do?  

The 80 percent hot flashes figure is not universal. Eighty to 85 percent of European and American women may experience hot flashes, but as few as 15 percent of women may be affected in places like Japan. In fact, there isn’t even a term for it in the Japanese language, which supports how relatively rare it is. Could the phytoestrogens in soy be helping

Researchers examined the “association between soy product intake and the occurrence of hot flashes” by following a thousand Japanese women over time, from before they started menopause, to see who developed hot flashes and who didn’t. As you can see at 2:34 in my video, those women eating around four ounces of tofu a day appeared to cut their risk in half, compared to women only eating an ounce or two a day, suggesting soy products are protective. But, could it be that soy intake is just a marker for a healthier diet over all? 

A study in China found that consumption of “whole plant foods” in general seemed to be associated with decreased menopausal symptoms, so in order to see if soy had a special role, you’d have to put it to the test.  

As you can see at 3:10 in my video, soy phytoestrogens in pill form showed extraordinary results, including a significant decrease in hot flash “presence, number [frequency] and severity.” At the start of the study, 100 percent of women suffered hot flashes, and that dropped to only 31 percent by the end of three months. The average number of hot flashes also dropped, from about 120 a month down to only 12 in 90 days. Exciting findings, but the problem with this study and some others like it is that there was no control group to control for the placebo effect. If you look at all the hormone trials, even the women who got the placebo sugar pills had up to around a 60 percent reduction in hot flashes over the years. That’s why any “therapies purported to reduce such symptoms must be assessed in blinded trials against a placebo or a validated therapy because of the large placebo effect…and also because…menopause symptoms often decline” on their own over time. 

To illustrate this point, see the findings of a study I show at 4:00 in my video. Researchers gave women a soy protein powder and saw a nice drop in hot flashes over the next 12 weeks. Those results on their own make the soy supplementation look pretty effective, but those were results from the placebo powder group. The study subjects who actually got the soy achieved results significantly better than placebo, which demonstrates how important it is to recognize how powerful the placebo effect can be. Over the past 20 years, more than 50 clinical trials have evaluated the effects of soy foods and supplements on the alleviation of hot flashes. Compiling the best ones together, the placebo groups got about a 20 percent drop in hot flash severity, while the soy groups achieved about a 45 percent drop. So, on average, the soy did about 25 percent better than control, as you can see at 4:31 in my video.  

There have been two studies that compared soy phytoestrogens head–to–head against hormones. In one study, they actually seemed pretty comparable, in terms of reducing hot flashes, muscle and joint pain, and vaginal dryness, compared to placebo, as you can see at 4:50 in my video. In the other study, however, soy did better than placebo, but estrogen and progesterone therapy did better than both. But, soy has “the benefit of no increased risk of breast and uterine cancer or cardiovascular disease,” such as heart disease and stroke.  


  • After menopause, a woman’s estrogen level drops by 95 percent, which benefits her endometrium, the uterine lining, and lowers breast cancer risk.
  • Soy phytoestrogens can block estrogen production, such that drinking a glass of soy milk at each meal can halve estrogen levels in premenopausal women.
  • Although estrogen treatments may effectively reduce symptoms of menopause, they have myriad downsides, including uterine cancer, blood clots, strokes, and cognitive impairment, and taking it with progesterone-type compounds may also increase heart attack, stroke, breast cancer, clot, and dementia risks.
  • Hot flashes are suffered by approximately 80 percent of postmenopausal European and American women, but only about 15 percent of women in Japan, for example.
  • Researchers found that those eating around four ounces of tofu a day appeared to halve their risk of hot flashes, compared to those who only ate one or two daily ounces, suggesting soy products are protective.
  • More than 50 clinical trials have studied the effects of soy foods and supplements on hot flashes, and the best studies found about a 25 percent improvement by soy over placebo controls in the severity of hot flashes.
  • Of the two studies comparing soy phytoestrogens against hormones, one determined soy to be fairly comparable with regards to reducing hot flashes, muscle and joint pain, as well as vaginal dryness, compared to placebo, while the other found that soy did better than placebo but the estrogen and progesterone therapy exceeded both in effectiveness.
  • Soy, however, provides the benefit without the increased risks of cancers of the breast and uterus or heart disease, stroke, and other cardiovascular disease.

Why does soy help some women, but not others? See my video How to Convert Into an Equol Producer. 

I discuss more about the risks of hormone replacement therapy in How Did Doctors Not Know About the Risks of Hormone Therapy?. 

What about Plant-Based Bioidentical Hormones? Check out the video and find out. 

For more on soy, see: 

In health, 

Michael Greger, M.D. 

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations: 

What Should We Do to Lower Lead Levels in Breast Milk?

Thu, 08/19/2021 - 07:00

What are the effects of sodium and calcium intake on blood lead levels in pregnant and breastfeeding women? 

Although our skeleton “has predominantly been considered a storage site for sequestering absorbed lead, bone is not simply an inert storage site. Once deposited in bone, lead can be remobilized from bone” back into the bloodstream if, for example, we lose bone due to osteoporosis. Even normal menopause can do it, raising lead levels as our bones start to lose their integrity, but the biggest concern is the “mobilization of long-term stores of lead from the maternal skeleton…during pregnancy and lactation.” In order to maintain maternal lead levels as low as possible during this critical period, we need to minimize bone loss.  

How do we do that? As I discuss in my video Should Pregnant Women Take Calcium Supplements to Lower Lead Levels?, “habitual excessive NaCl [salt] intake could be a factor in promoting bone loss.” So, is there a relationship between maternal sodium intake and blood lead levels during pregnancy? Researchers found that higher salt intake was associated with higher lead levels, but only for women who were getting less than 840mg of calcium a day. “The findings…suggest that adequate Ca [calcium] with a low Na [sodium] intake may play a beneficial role in decreasing the blood Pb [lead] concentration in pregnant women.”  

Higher calcium intake has been associated with lower blood lead concentrations during pregnancy, but you don’t know if it’s cause and effect unless you put it to the test.   

What if you gave women calcium supplements? I’ve previously explored how milk may actually make things worse, but what about just straight calcium, especially for women with low calcium intake? Study participants, African women who had been getting only 350mg of calcium a day, which is only 35 percent of the 1000mg RDA, were given a whopping 1,500mg of daily calcium. That will protect their bones, right? As you can see at 2:00 in my video, without the calcium, when the women were getting only 350mg of calcium a day in their diet, they lost some bone in their spine and hip. How did they do when researchers gave them 1,500mg of calcium a day? They lost even more bone. The women who had received the calcium supplements had a significantly lower bone mineral density at the hip and greater bone loss in the spine and wrists. 

What happened? It looks like the researchers messed up the women’s body’s natural adaptation. At the start of the study, they had only been eating 350mg of calcium a day. Because our body isn’t stupid, they were maximizing absorption and minimizing loss. Then, the researchers stepped in with calcium pills and undermined the whole process, turning off those adaptations and leaving their body thinking they were always going to get those massive calcium doses. When the study stopped, the women went into major calcium deficit and had to steal more from their bones. They researchers went back later on and found that although the women who had been in the placebo group bounced back, those given the extra calcium continued to suffer the effects, as you can see at 3:04 in my video

What about in Western women who are already taking in more than 1,000mg of calcium a day? Would giving them an extra 1,200mg a day cut down on some of that bone flux? Yes, it did seem to cut down on bone resorption by about 16 percent, “and, thus, may constitute a practical intervention to prevent the transient skeletal loss associated with childbearing,” which could release any lead trapped there, but you don’t know until you put it to the test. 

In a different paper from the same study, the researchers measured what was happening to the women’s lead levels. That drop in bone borrowing led to a drop in lead release. As such, it may help lower lead exposure to both the fetus and the infant, as the benefits continue through breastfeeding. Okay, but the women in this study were living in Mexico City, where they may have been exposed to lead-glazed ceramics with lead levels approaching 10 ug/dL. What about women with lead levels closer to the current U.S. average under 5 ug/dL?  

Researchers randomized half the breastfeeding women in their study to take 500mg of extra calcium a day. As you can see at 4:25 in my video, the lead levels of both groups started out the same during pregnancy. In the non-supplemented group, those levels shot up during breastfeeding, as presumably some of the lead was released from their bones. In the group getting the daily 500mg calcium supplement, however, there was no spike in lead in their bloodstream, providing “evidence that calcium supplementation during lactation [breastfeeding] may be effective in limiting mobilization of lead from bone stores, thus reducing the risk of lead transfer to the nursing infant through mother’s [breast] milk.”  

Regardless, breast is still best. Supplementation or not, “the risks are outweighed by the benefits of breast milk consumption,” but calcium supplementation may help reduce any risk even further. Of course, it’s better not to build up lead in your bones in the first place. As a famous occupational medicine paper put it a half–century ago, there are all methods of dietary interventions, but there is only one way to prevent lead poisoning: Don’t get poisoned in the first place. Anything else just diverts attention from treating the underlying cause. 

For other toxic heavy metals, such as mercury, for example, women are “advised to avoid the consumption of predatory fish”—that is, fish-that-eat-other-fish—“during pregnancy and when breastfeeding to decrease MeHg [mercury] exposure.” In fact, they should start even before pregnancy. Indeed, “women of child–bearing age and nursing mothers should avoid consuming piscivorous [fish-eating] fish” to avoid building up the mercury in the body in the first place. And, for lead, that means not living next to a smelter plant and avoiding smoking.  

There is one other way to detox your body of lead to protect some of your future children, but it’s not ideal. Remember that menopause study, where postmenopausal women had higher blood lead levels than premenopausal women? Well, even higher still were postmenopausal women who had never had children. As you can see at 6:00 in my video, “The postmenopausal increase in lead levels was less in women with prior pregnancies,” presumably because they had already detoxed some of their lead into their children. 


  • Lead, once deposited in bone, can flood back into our bloodstream when bone is lost, for example, due to osteoporosis, menopause, pregnancy, and lactation.
  • Researchers found that higher intake of salt was associated with higher levels of lead for women getting less than 840 mg of daily calcium and suggest that adequate calcium intake with low sodium consumption may be beneficial in decreasing blood lead levels in women during pregnancy.
  • When African women who had been getting 350 mg of daily calcium from their diet (just 35 percent of the RDA) were given 1,500 mg a day via supplement, they lost even more bone. It appears their natural adaptation was disrupted and their body expected the massive calcium influx such that they went into major deficit when the study concluded and the supplement was no longer taken so more calcium was taken from the stores in their bones.
  • Researchers randomized breastfeeding women to take an extra 500 mg of daily calcium and found that the lead levels in the non-supplemented group increased during breastfeeding, likely due to some lead being released from their bones, whereas there was no spike in blood lead levels in the group taking 500 mg of calcium a day, suggesting that calcium supplementation during lactation may limit lead mobilization from bone stores and reduce transfer risk to nursing infants.
  • Breastmilk is still preferred, but calcium supplementation may be reduce further risk.
  • Preventing lead poisoning is important, just as avoiding other toxic heavy metals, such as mercury, found in many fish.

In case you missed the last video, The Rise in Blood Lead Levels at Pregnancy and Menopause offers some background on this issue. 

The video I mention about milk making things worse is How to Lower Lead Levels with Diet: Breakfast, Whole Grains, Milk, Tofu?.

Note that whole–food sources of calcium may be preferable, as I document in my video Are Calcium Supplements Safe?

For more on pregnancy detox, see: 

In health, 

Michael Greger, M.D. 

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations: 


Why Blood Lead Levels Rise at Pregnancy and Menopause  

Tue, 08/17/2021 - 07:00

The lead trapped in our skeleton can leach back into our bloodstream when we temporarily or permanently lose bone due to pregnancy, weight loss, menopause, or osteoporosis. 

The half-life of lead in the bloodstream is only about a month. In other words, if you feed people lead for about a hundred days to boost up their blood levels and then you stop giving them lead, the levels in their blood starts to drop, such that within about 30 days, their lead levels are cut in half. In another month, they’re cut in half again. So, by around three months, their body is able to remove about 90 percent from their bloodstream. You can see a graphic depicting this at 0:10 in my video The Rise in Blood Lead Levels in Pregnancy and Menopause.  

If you’re chronically exposed to lead, however, you can have chronically high lead levels in your blood. More than half a million kids in the United States have concerningly high lead levels, and “poor people…in politically disempowered communities of color are most at risk of lead poisoning,” regardless of age. 

If you don’t live in those communities and are not constantly exposed to lead, why should you care about dietary strategies to lower the lead level in your own blood, if your body is already so good at it? Even if you do get exposed to lead here and there, about 90 percent of the lead in your blood is gone after just three or four months. Ah, but gone where?  

More than 90 percent of lead in our body “is stored in our bone where it has a half-life of years to decades,” so instead of it taking a few months to get rid of it, how about a few decades? Indeed, researchers estimate the half-life of the tibia, commonly known as shinbone, to be 48.6 years. So, even if we moved to some other planet and never had any further exposure to external sources of lead, we still have an internal source of lead leaching the toxic heavy metal into our system throughout our life. 

Okay, but if it’s mostly just stored in our skeleton, what’s the big deal? Well, if you were to lose bone, all the trapped lead could come flooding back into your system. For example, when we lose weight, we lose bone, which makes a lot of sense. Heavier people have a heavier skeleton with greater bone mineral density. Their body has to maintain stronger bones to carry around all that extra weight. So, if we lose weight, do the levels of lead in our bloodstream go up as our skeleton downsizes? As you can see at 2:14 in my video, the answer, unfortunately, is yes—but only if we lose a lot of weight. If you lose 10 pounds or so, not much happens, but if you lose more like 80 pounds, the lead levels in your blood can rise 250 percent. 

When else can you experience bone loss? With osteoporosis, obviously. As you can see at 2:31 in my video, women with osteoporosis can lose an average of 3 percent of their bone mass a year. However, even healthy, postmenopausal women without osteoporosis may lose a percentage of their skeleton annually. So, do the lead levels in women go up when they lose their periods? Apparently so. A study of nearly 3,000 women found “a highly significant increase” in lead levels after menopause, which “provides evidence that bone lead is in fact mobilized into blood…A major implication of this finding is that even low level lead exposure, over a relatively long time, may result in increased body burdens of lead which would be releasable in toxicologically significant amounts during critical physiological states” where bone is in flux. So, it’s not just osteoporosis, but, most seriously, during pregnancy and lactation. 

Most of the calcium the baby gets in utero comes from “increased maternal absorption” of dietary calcium. The mother’s gut starts absorbing 60 or 70 percent more calcium in the second and third trimesters to build the baby’s skeleton. That’s why women’s dietary calcium requirements are not increased by pregnancy or breastfeeding. Your body’s not stupid. When it realizes it needs more calcium, it just absorbs more calcium. Now, when that isn’t enough, you do end up dipping into the calcium stored in your bones. That isn’t a problem, though, because after it’s all over, your body puts the calcium back into your skeleton, such that six months after delivery, after giving birth, your bone mineral density is right back where you started.  

That’s why, as you can see at 4:10 in my video, even those women who breastfeed for a long time, well past those six months after giving birth and having had multiple pregnancies, end up with no compromise to their bone mineral density later in life, whether measured in their wrists, spine, or hips. So, why does it matter if your body makes a withdrawal from the bone bank during pregnancy and lactation, if it ends up just depositing it all back? Because of the lead. When your body dissolves some of your bone to borrow that extra calcium, it releases the lead that had been locked in the skeleton at the worst possible moment—right when your baby is most vulnerable. That is part of “lead’s toxic legacy.”  


  • Chronic lead exposure can result in chronically high blood lead levels, which affect more than a half-million children in the United States. At highest risk of lead poisoning are lower-income communities of color regardless of age.
  • Lead in our bloodstream has a half-life of about a month, which means half of the amount of lead will be cut in about 30 days if intake is stopped. The following month, half of the remaining level will be cut, and so on.
  • More than 90 percent of the lead in our body, however, is stored in our bone with a half-life of years to decades instead of a month. For instance, the half-life of lead in our shinbone is 48.6 years.
  • The lead trapped in our bones can flood back into our system when bone is lost, for example, due to weight loss, osteoporosis, post-menopause, pregnancy, and lactation.
  • During pregnancy, most of the calcium gotten by the fetus to build their skeleton comes from the mother’s increased absorption of dietary calcium or stored calcium from her bones. Her body recognizes that more calcium is needed during pregnancy, so it simply absorbs more or pulls more from her skeleton.
  • After delivery, the mother’s bone mineral density is replenished and her body replaces the calcium back into her skeleton, however, the issue is the lead that is released when the body dissolves some bone for that needed extra calcium, pulled when the fetus is most vulnerable.

What can we do about it? You can find out in my video Should Pregnant Women Take Calcium Supplements to Lower Lead Levels?

To see my other videos on lead, check out: 

In health, 

Michael Greger, M.D. 

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations: 

The Dangers of Talcum Powder

Thu, 08/12/2021 - 07:00

What role does diet and baby powder play in the development of fibroids and ovarian cancer? 

If you randomly select a group of women and ultrasound their uterus, most of them have fibroid tumors by age 50—and by most, I mean more than 80 percent of black women and nearly 70 percent of white women. As you can see at 0:23 in my video Talcum Powder and Fibroids, half of the white women in study already had fibroids by their early 40s, while half of the African-American women had them even early, by their mid-30s. 

After getting over the shock of how widespread fibroids are, the next question becomes, Why the racial disparity? Is it “diet, stress, [or] environmental exposures”? Perhaps the reason could offer a clue as to what causes fibroids. For example, African Americans tend to have lower intakes of fruits and vegetables, and fruits and vegetables appear protective against fibroids. (Citrus are particularly protective, though apparently not just citrus juice, as found in the Black Women’s Health Study.) 

It’s interesting that if you measure the levels of beta-carotene in fresh surgical tissue samples of uterine fibroids and adjacent normal uterine tissue obtained during hysterectomies, you find significantly lower concentrations in the fibroids. In fact, as you can see at 1:23 in my video, beta-carotene was not even detectable in half the fibroid specimens, and the same was found in cancer: Most cancerous tissues tested had undetectable levels of beta carotene, compared to the normal tissue right next to the tumor. Could it be that decreased levels of beta-carotene somehow play a role in causing these conditions? Sounds like a bit of a stretch, but you don’t know until…you put it to the test.  

There had never been a randomized controlled clinical trial of fruits and vegetables for fibroids, until… never. Researchers did do a randomized controlled trial of kind-of-a-fruit-and–vegetable-at-the-same-time studying tomatoes for the prevention of fibroids, but they studied fibroids in Japanese quail—as in the birds. That doesn’t really help me help my human, non-quail patients. 

The action of lycopene, the red pigment in tomatoes, “in an animal model may not accurately represent lycopene action in humans.” And, indeed, the Harvard Nurse’s study found no apparent link between lycopene consumption and fibroids, as you can see at 2:27 in my video. So, yes, fruits and green vegetables at least may have a protective effect, but we won’t know for sure until they’re properly put to the test.  

Vitamin D level is another possible factor as to why African Americans disproportionately suffer from fibroids, since women with darker skin are more likely to be deficient in the vitamin. As many as 80 percent of black women may have inadequate levels of vitamin D, compared to only one in five white women. 

Vitamin D does inhibit fibroid cell proliferation, at least in a petri dish, and it may be able to shrink tumors in your pet rat, but what about in people? A population study did find that women with “sufficient vitamin D” levels in their blood had about one-third lower odds of fibroids, consistent with the finding that women who report lots of sun exposure also appear to be protected, but until there’s an interventional trial where women are randomized to vitamin D or a placebo, we won’t know for sure if vitamin D plays a role in fibroid prevention or treatment. 

African-American women are also more likely to sprinkle baby powder on their genitals, which may not only double the odds of fibroids, but may also increase the risk of ovarian cancer, the deadliest gynecological cancer. Internal memos show Johnson & Johnson knew about the cancer risk, but still decided to target African Americans. In an advertisement depicting an African-American family that you can see at 4:04 in my video, Johnson & Johnson said, “Think of us as a lifetime friend of the family”—perhaps a lifetime cut short by its baby powder. At least that’s what a jury found in 2017 when it awarded a woman $110 million in damages, and that was on top of the $200 million in verdicts from 2016, with thousands of lawsuits pending after internal memos revealed that, decades ago, Johnson & Johnson’s own contracted toxicologists were warning the company there are multiple studies showing a cancer link. “Anyone who denies this risks that the talc industry will be perceived by the public like it perceives the cigarette industry: denying the obvious in the face of all evidence to the contrary.” 


  • Fruits and vegetables appear to be protective against fibroids, and African Americans tend to have lower intakes of these plant foods.
  • Fibroids are widespread amongst women, with more than 80 percent of Black women and nearly 70 percent of White women having fibroid tumors by age 50, as determined by uterine ultrasound, and African-American women seeming to get them at an earlier age.
  • When measuring levels of beta-carotene, significantly lower concentrations are typically found in fibroids and cancerous tissues.
  • A randomized controlled clinical trial of fruits and vegetables for fibroids has never been conducted, so, although we know fruits and green vegetables appear to be protective, we cannot know for certain until put to the test in an interventional trial.
  • African Americans may suffer disproportionately from fibroids due to inadequate levels of vitamin D.
  • Sprinkling baby powder on genitals may not only double the odds of fibroids, but also increase ovarian cancer risk, and African American women are more likely to do this than White women.
  • Johnson & Johnson was aware of the cancer risk but, according to internal memos, still chose to target African Americans in its baby powder ad campaigns.
  • Juries have awarded hundreds of millions of dollars in damages in verdicts from lawsuits filed against the company, with thousands more suits pending.

When I started this article’s corresponding video, I profiled the effects of diet and supplements of fibroid tumors, but then I got dragged off on that horrifying ovarian cancer tangent—and I’m so glad I did. What a story! No wonder corporations are working hard to pass tort reform to limit the amount of damages they have to pay for their negligence or malfeasance. If you remember, it was a series of landmark court cases that also dragged damning internal tobacco industry communications into the light. For a bit on that story see: 

In health, 

Michael Greger, M.D. 

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations: 



What Is the Science on Cannabis?

Tue, 08/10/2021 - 07:00

What did the National Academies of Sciences’ 468-page report conclude about cannabis? 

When some misinformed people hear of the grand opening of a new plant-based medical practice, one plant in particular may come to mind. I’ve gotten a lot of questions about cannabis over the years, and I figure it’s high time to try to clear the haze. I didn’t want to just take a pot shot, just a tokin’ effort, and end up with a half-baked puff piece. There are burning issues about a growing industry. With so much buzz and smoke and mirrors, the science can really take a hit. Are there acute chronic effects? Perhaps blunt trauma from impaired driving? I wanted to give the straight dope and weed out any doobie-ous research. It’s been quite a trip. In fact, 420 articles were published within just a few months! 

My video The Institute of Medicine Report on the Health Effects of Marijuana dives into the review everyone was waiting for: the 2017 “current state of evidence” from the Institute of Medicine “tasked with conducting a comprehensive review of…the health effects of using cannabis and cannabis-derived products.” The reviewers started with 24,000 sources, which they whittled down to about 10,000 from which they produced a 468-page document. What did they find? 

I think it’s fair to summarize that they found the purported benefits to be much smaller and weaker than are often reported, but they found the same for the purported risks. So, that’s good news for the recreational user who is mostly just worried about not getting cancer, but it’s bad news for the patient who actually wants it to help their cancer. They did find “substantial evidence” for some benefits, but only three—in the treatment of chronic pain in adults, the treatment of chemotherapy-induced nausea and vomiting, and for relieving self-reported muscle tightness in patients with multiple sclerosis. Even archetypal medical marijuana indications, like glaucoma, failed to live up to expectations. 

“Despite popular belief to the contrary, extensive research over decades has documented that marijuana is not effective in the management of clinical glaucoma,” a disease of increased pressure within the eyeball. Marijuana does lower pressure, but only for about an hour, so you’d have to smoke a dozen or so joints a day. Even if you did smoke those few thousand joints a year, though, your body gets used to it, so what little benefit there is disappears within a few months in most patients. 

On the other hand, conspicuously missing from the list of adverse side effects of long-term or heavy marijuana use, which you can see at 2:42 in my videois any mention of chronic, obstructive, pulmonary diseases like emphysema, which you can get from smoking tobacco. Similarly, it doesn’t look like smoking marijuana increases the risk of respiratory cancers, such as lung cancer or head and neck cancer, though cannabis may increase the risk of testicular cancer. There have been three studies so far on marijuana use and testicular cancer. As you can see at 3:10 in my video, marijuana appears to increase risk about 50 percent, but only, it seems, for those smoking once a week or more, or for ten years or longer. 

What did the Institute of Medicine conclude overall in its 468-page report? Were they for legalization, or opposed? Basically, they concluded that there simply isn’t enough research, “leaving patients, health care professionals, and policy makers without the evidence they need to make sound decisions regarding the use of cannabis and cannabinoids” either way. Further, “this lack of evidence-based information…poses a public health risk.” 

The one thing everyone on both sides “can agree [on] is the need for definitive clinical research on marijuana.” Otherwise, we’re just left with “anecdotes, Internet blogs, and advertisements [that] do not provide a sound basis for assessing the safety and efficacy of pharmacologic agents.”  

“Because cannabis is a naturally occurring plant and cannot be patented,” the pharmaceutical industry is MIA. What we need are large clinical trials. Until then, “we’re still going to be left scratching our heads,” but where will the funding come from? For drug companies, interest in the plant is scant” because where’s the “payback”? 

Big Pharma is interested in a “reasoned approach,” however. Writes pharmacology professor Harold Kalant, one day, “the development of newer…endocannabinoid modulators”—in profitable pill form, that is—“will make the use of herbal cannabis a thing of the past.” 

Why is there such a “dearth of rigorous research on the effects of marijuana”? The first major study wasn’t published until 2007. “Why did it take so long for this study to appear in the peer-reviewed scientific literature? Why did the pharmaceutical industry fail to show any interest in this promising compound? Some might prefer a simple answer: since marijuana is a naturally-occurring botanical”—since it’s just a plant—”it cannot be patented, thus removing any incentive for investing…corporate funds…” Yes, but it’s more complicated, as I discuss in my video Researching the Health Effects of Marijuana

In fact, research funds are available—“$111 million…in 2015 alone,” for example—but, historically, “that money generally has been obtainable only for research on the negative effects of cannabis.” In the United States, cannabis is still officially lumped in with heroin as a Schedule I drug, which means that, by definition, it is classified by the government as having no medicinal value. “This designation has resulted in a near-cessation of scientific research,” particularly because the only way researchers could get cannabis without risking jail time is from the only federally authorized source, a strain grown in Mississippi and controlled by the National Institute on Drug Abuse. What’s more, historically, the NIDA has only greenlit research aimed at demonstrating “harmful effects.” 

“Residents of 23 US states can buy medical marijuana…but US scientists must wade through onerous paperwork to score the drug for study.” And, even when they do get it, it may be the wrong stuff. The cannabis from that one federally authorized farm in Mississippi “‘may differ substantially’ from what people purchase for real-world consumption”—that is, it may not be what people are actually using these days. As a result, the studies coming out may be on your grandma’s grass, for instance, “with potency levels between 3.5 and 7.0% THC,” whereas the marijuana available these days may be ten times more potent.  

So, there is a crazy “catch-22,” where “the cannabis that should be studied…is illegal and the cannabis that can be legally studied—the decades-old Mississippi strain—is essentially kept off-limits.” Because of this, “ill-informed practitioners are thus left to make do with anecdotal testimony and case reports—the least rigorous form of evidence—to guide their prescribing.” Basing treatment off stories from the internet is bad medicine. 

“As long as clinical research on Cannabis is controlled by regulators expressly opposed” to the stuff, we may miss out on potential benefits—but that’s no excuse. Just because there are political barriers to research doesn’t mean we should lower our bar in terms of demanding evidence. “The sick still need medically sound treatments.” 

Of course, there’s now pressure coming from both sides. The marijuana industry has become big business and, with its billions, can rally the troops. “Cannabis researchers already talk of being bombarded with e­mails from pro­cannabis groups if they make any negative comments about the drug. ‘Marijuana research is like tobacco research in the ’60s,’” says one University of Colorado researcher. So now, there’s fear Big Money will push the pendulum too far the other way.  

The barriers go beyond money, politics, and prejudice, though. Cannabis research is hard to do. How do you do a double-blind study with marijuana? People know when they’ve been duped with placebo dope, and they can tell the difference between pot brownies and regular brownies. So, if you know you’re getting the active drug, the placebo effect can kick in hard, especially when you’re dealing with subjective outcomes like pain or mood. 

And imagine if you’re trying to do a population study on memory or cognitive impairment, and you have to ask heavy pot smokers to try to remember how much they’ve smoked over their life. You can guess how that might “influence data accuracy.” 

Let me give you an example of how convoluted this can get. Neuropsychological testing of cannabis users have found residual negative effects in terms of scoring slightly lower on memory tests, but how do we know that wasn’t just a matter of motivation (or lack thereof), rather than actual cognitive impairment? That had never been tested until researchers gave a group of potheads a standard learning test with the instruction: “Please complete the following series of tasks which measure different areas of cognition, like memory and attention.” With that standard spiel, pot smokers scored significantly worse than non-users, as you can see at 4:35 in my video. Okay, but what if the study participants heard the standard spiel and were also told: “It is important that you try your very best on these tasks, because this research will be used to support legislation on marijuana policy.” So, one might infer that if you do good, weed might get decriminalized or something! And, under those circumstances, BOOM—the apparent cognitive impairment disappears, as you can see at 4:57 in my video.  

Now, you could argue that lack of motivation is a problem in and of itself, but it’s better than having long-term brain damage. 


  • Tasked with conducting a comprehensive review of the health effects of cannabis, the Institute of Medicine released a 468-page report.
  • In sum, the researchers found less benefit but also less risk than is often claimed.
  • Substantial evidence was found for the treatments of chronic pain in adults and chemotherapy-induced nausea and vomiting, as well as relieving self-reported muscle tightness in individuals with multiple sclerosis, but not for the management of glaucoma, despite popular belief otherwise.
  • Unlike smoking tobacco, long-term or heavy marijuana-smoking habits do not appear to have the same adverse side effects of chronic, obstructive pulmonary diseases like emphysema, and smoking cannabis does not seem to increase risk of respiratory cancers, though it may elevate testicular cancer risk.
  • Overall, the Institute of Medicine determined there is a lack of evidence-based information, which poses a risk to public health.
  • One reason cannabis is under-studied is that it is a naturally occurring plant that cannot be patented, so drug companies are disinclined to invest in research about its effects. What’s more, most research that has been conducted has focused on its negative impacts.

If you’d like to learn more about the effects of marijuana on health, check out: 

In health, 

Michael Greger, M.D. 

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations: 

The Effect of Avocados on Small, Dense, LDL Cholesterol

Thu, 08/05/2021 - 07:00

What are the effects of oatmeal, walnuts, extra virgin olive oil, and avocados on LDL cholesterol size? 

When a headline reads “Avocados could improve your cholesterol—and more,” the article and others like it are largely talking about substitution experiments, where avocado is added to the diet as a replacement for animal fats. In that case, it’s no wonder cholesterol goes down. Dairy and poultry are the two greatest contributors of cholesterol-raising saturated fat intake, so if you take people eating a standard North American diet including animal fats, they may start out with an LDL cholesterol level up around 95mg/dl. If you add avocado to their diet without doing anything else, their cholesterol does not go down; instead, it may go up to around 105mg/dl. If you add avocado while reducing saturated fat intake, though, cholesterol falls to about 90mg/dl—but that drop isn’t very different from what you’d get by just reducing saturated fat and adding nothing, which was shown to give an LDL under 90mg/dl, as you can see at 0:34 in my video Avocados Lower Small Dense LDL Cholesterol

What if you compared the effects of eating no meat at all with a meat-free diet that included avocado? Researchers took people with sky-high cholesterol levels up around 300mg/dl and switched them to either a relatively low-fat vegetarian diet with about 20 percent of calories from fat or a vegetarian diet with added avocado that took it up about 30 percent of calories from fat, which is a more typical fat content. As you can see at 1:22 in my video, the study participants started out with LDLs through the roof, and, while cutting out meat may have helped, cutting out meat and adding avocado seemed to help even more—and it may help best with the worst type of LDL.  

As I’ve touched on before, all LDL cholesterol is bad cholesterol. However, large, fluffy LDL may only increase the odds of cardiac events such as heart attacks by 31 percent, whereas small, dense LDL is even worse and increases the odds by 44 percent.  

If you feed people a lot of oatmeal and oat bran, not only does that cause their LDL to go down overall, but it specifically brings down the small LDL, the worst of the worst. What happens if you add walnuts to a low-fat diet? As you can see at 2:04 in my video, LDL goes down and, at the same time, the size distribution of the LDL shifts to be a little more benign. What if you put people on a plant-based diet with lots of fiber and nuts? As shown as 2:15 in my video, you can get a massive 30 percent drop in LDL, a drop that is comparable to a cholesterol-lowering statin drug. What’s more, this includes a drop in the small, dense LDL, which is the most dangerous.  

This does not happen with extra-virgin olive oil, however, so it’s not just a monounsaturated fat effect. In the famous PREDIMED study, which you can see at 2:35 in my video, those randomized to the extra nuts group got a significant drop in the smallest, densest LDL, but those randomized to the extra-virgin olive oil group did not. So, there appears to be some special components in nuts that lowers the worst of the worst LDL cholesterol.  

Do avocados offer similar benefits? We didn’t know until the first randomized controlled feeding trial to look at avocados and LDL size. The researchers removed animal fat from people’s diet and replaced it with either carbohydrates, avocado, or vegetable oils that had a similar fat profile to the avocados. In this way, the avocado group and the vegetable oil group were put on very similar diets, except one had the nutrients unique to avocados and the other did not.  

What happened? 

Any time you lower intake of saturated fat, such as replacing animal fat with plant fat (vegetable oil in this case) or carbohydrates, you’re going to bring down LDL. Okay, but does replacing animal fat with the whole plant food avocado make a difference? Yes. That resulted in an even better effect. To see why, the researchers broke the LDL down into large versus small. All three treatments brought down the dangerous large LDL, but the avocado had the additional effect of also bringing down the super dangerous small LDL. That’s where that extra drop came from. You can see a graph depicting these findings at 3:27 in my video

 So, it’s not just a matter of replacing animal fat with plant fat. There are additional benefits to the fiber and phytonutrients of whole plant foods like avocados. 

If there’s something good in avocados, should we just add avocado extracts to meat? Well, incorporating avocado extracts into pork patties evidently reduces the meat’s cholesterol oxidation products that “have been well documented” to be toxic, carcinogenic, and atherosclerotic, but it doesn’t eliminate them. 


  • Dairy and poultry are two of the most significant contributors of cholesterol-raising saturated fat in the diet.
  • Simply adding avocado to the diet without also reducing saturated fat intake does not appear to lower cholesterol and, in fact, may cause it to rise.
  • Substitution experiments, where avocado replaces animal fats in the diet, have shown improvements in cholesterol, however, the drop does not appear to differ much from just reducing saturated fat consumption without adding anything else.
  • Comparing the effects of a meat-free diet to a meat-free diet with added avocado, researchers found that eschewing meat while also adding avocado helped even more than merely skipping meat, and it may help more effectively with the worst type of bad LDL cholesterol, small, dense LDL.
  • Oatmeal, oat bran, walnuts, and a plant-based diet rich in fiber and nuts have all been shown to cause LDL to lower overall and the more dangerous, small LDL, specifically, but this was not seen with extra-virgin olive oil, suggesting it is not only a monounsaturated fat effect.
  • Researchers removed animal fat from subjects’ diets and replaced it with either carbohydrates, avocado, or vegetable oils with similar fat profiles to avocados and found that replacing the animal fat with the whole plant food avocado had the best results in reducing LDL.
  • All three treatments lowered large LDL, but avocado had the added effect of also lowering the more dangerous small LDL.

What about the effects on cholesterol of people not consuming plant-based diets? See my video Are Avocados Good for Your Cholesterol?. 

 For more information on large, fluffy LDL versus small, dense LDL, check out Flashback Friday: Does Cholesterol Size Matter?.

And, if you love avocados as much as I do, you may be interested in: 

In health, 

Michael Greger, M.D. 

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations: 


What Do Avocados Do to Your Cholesterol?

Tue, 08/03/2021 - 07:00

Can guacamole lower your cholesterol as well as other whole-food fat sources like nuts, or is that just spin by the avocado industry? 

“Avocados are the richest known fruit source of phytosterols,” the cholesterol-lowering nutrients found in plant foods, brags a review sponsored by the HASS Avocado Board. The operative word, though, is fruit. 

Yes, avocados contain more phytosterols compared to other fruit, but phytosterols are fat-soluble substances. Most other fruits hardly have any fat in them at all, so avocados will obviously come out on top compared to other fruit. What if you compare phytosterol content of avocados to nuts and seeds, though? One avocado has about 100 milligrams of phytosterols. On the same scale, sesame seeds and tahini have 400 milligrams; pistachios, pumpkin seeds, and sunflower seeds have about 300; almonds, almond butter, flaxseeds, and macadamia nuts have around 200; and even chocolate has about twice as many phytosterols as avocados, as you can see at 0:51 in my video Are Avocados Good for Your Cholesterol

Even though nuts and seeds have the highest levels of phytosterols overall, the studies that have been done on lowering “bad” LDL cholesterol with phytosterols have used supplements starting with 600 milligrams and going up into the thousands. So, yes, you can lower LDL cholesterol by about 8 percent with a dose of phytosterols around 2,100 milligrams, but that would be 20 avocados a day, as you can see at 1:17 in my video. And 2,100 milligrams of phytosterols would also be a lot of nuts, but you can get an 8 percent drop in LDL by just eating a palmful of nuts, just a single ounce a day, as you can see at 1:36 in my video. So, phytosterols aren’t the only components of nuts responsible for driving down cholesterol. Nuts must have other components, perhaps fiber or other phytonutrients, that contribute to their cholesterol-lowering effects. Might avocados have such components, too? You don’t know until…you put it to the test. 

 As you can see at 2:10 in my video, there are studies dating back more than a half century that appear to show that if you add an avocado to people’s daily diets, their cholesterol drops. When you remove the daily avocados, however, their cholesterol goes back up, and then it drops down again when you add the avocados back in. The data are pretty convincing—until you see how the study was done. The researchers didn’t just add an avocado. They swapped out animal fat. No wonder their cholesterol went down! Rather than a study about cholesterol and avocados, it may have just as well been about cholesterol and being on or off lard—and nearly all the studies on cholesterol and avocados are like this. 

What happened when researchers performed a meta-analysis of ten studies involving hundreds of people? When they put them all together and looked at the results, what did they find? It appears that adding avocados led to a significant drop in cholesterol and triglycerides—an average of about a 17-point drop in bad LDL cholesterol. But, nearly all of the studies were substitution studies, where saturated fat was removed from people’s diets and avocados were substituted in. If you cut down on saturated animal fat, your cholesterol will drop regardless. You can tell this review was not funded by the avocado industry because the researchers point this out, saying that “it is important to note that substituting avocados for saturated dietary fats as opposed to adding avocado to an already established baseline diet poses the greatest benefit.” Simply adding avocado may confer no benefits to cholesterol at all. 

So, yes, the avocado industry is right in saying that avocados are “a healthy substitute for butter / margarine, cheese, cream cheese,” but that’s a pretty low bar. 


  • Compared with all other fruits, avocados contain more phytosterols, the cholesterol-lowering nutrient found in plant foods, but phytosterols are fat-soluble and most fruits are very low in fat, so it isn’t surprising that avocados top the chart.
  • When comparing phytosterol content of avocados, chocolate, nuts, and seeds, to scale, nuts and seeds have the highest levels overall and even chocolate has roughly twice the phytosterols as avocados.
  • So-called bad LDL cholesterol may be lowered with doses of phytosterols equivalent to around 20 avocados or a single ounce of nuts (around a palmful) a day.
  • Most studies showing that cholesterol drops when a daily avocado is consumed and rises again when avocados aren’t eaten before falling once more when they’re resumed did not only add avocado to the subjects’ diets, but they swapped out animal fat, so it’s no wonder cholesterol went down with avocado consumption.
  • Removing saturated fat from the diet and substituting in avocados may lead to a significant drop in cholesterol and triglycerides, but simply adding avocado without also reducing saturated animal fat intake does not appear to result in any benefits to cholesterol.

What about adding avocado to a plant-based diet? Would there be any benefit then? Learn more:  

Why do we care about cholesterol? See, for example:  

What should we shoot for? See Flashback Friday: Optimal Cholesterol Level. 

To learn more about cholesterol-lowering foods, check out The Best Food for High Cholesterol and The Benefits of Kale and Cabbage for Cholesterol.  

In addition to adding cholesterol-lowering foods, we also need to reduce our intake of cholesterol-raising foods. See:  

In health, 

Michael Greger, M.D. 

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations: 


Dr. Greger’s Daily Dozen Healthiest of Healthy Foods 

Thu, 07/29/2021 - 07:00

In my book How Not to Die, I center my recommendations around a Daily Dozen checklist of everything I try to fit into my daily routine. 

In my book How Not to Die, I suggest we try to center our diets around whole plant foods. Some plants are healthier than others, though. Apparently, you can live for extended periods eating practically nothing but white potatoes, for example, and, by definition, that would be a whole food, plant-based diet—but not a very healthy one. All plant foods are not created equal. 

The more I’ve researched over the years, the more I’ve come to realize that healthy foods are not necessarily interchangeable. Some foods and food groups have special nutrients not found in abundance elsewhere. For example, sulforaphane, the amazing liver-enzyme detox-boosting compound, is derived nearly exclusively from cruciferous vegetables. You could eat tons of other kinds of greens and vegetables on a given day and get no appreciable sulforaphane if you didn’t eat something cruciferous. Same with flaxseeds and the anticancer lignan compounds: Flax may average a hundred times more lignans than other foods. And mushrooms? Well, mushrooms aren’t even plants. They belong to an entirely different biological classification and contain some nutrients like ergothioneine that may not be made anywhere in the plant kingdom. So, technically, maybe I should be referring to a whole food, plant- and fungus-based diet…but that sounds a little gross. 

It seems like every time I come home from the medical library buzzing with some exciting new data, my family rolls their eyes, sighs, and asks, What can’t we eat now? Or they’ll say, Wait a second. Why does everything seem to have parsley in it all of a sudden? They’re very tolerant! 

As the list of foods I tried to fit into my daily diet grew, I made a checklist and put it up on a little dry-erase board on the fridge, and we made a game out of ticking off the boxes. This evolved into my Daily Dozen, the checklist of everything I try to fit into my daily routine. In my video Dr. Greger’s Daily Dozen Checklist, you can see the list, the daily minimum servings I recommend, and examples of foods that go into each category. My Daily Dozen includes Beans, Berries, Other Fruits, Cruciferous Vegetables, Greens, Other Vegetables, Flaxseeds, Nuts and Seeds, Herbs and Spices, Whole Grains, Beverages, and Exercise. 

By Beans, I mean legumes, which also include split peas, chickpeas, and lentils. It may not seem like you’re eating beans when you have a bowl of pea soup, for example, or dip carrots into hummus, but you are. We should try to get at least three servings a day. A serving is defined as a quarter cup of hummus or bean dip; a half cup of cooked beans, split peas, lentils, tofu, or tempeh; or a full cup of fresh peas or sprouted lentils. Technically, peanuts are legumes, but, nutritionally, I put them in my Daily Dozen Nuts and Seeds category. Similarly, I put green beans, snap peas, and string beans into the Other Vegetables category. 

My Daily Dozen includes at least one serving of Berries a day, which is a half cup of fresh or frozen, or a quarter cup of dried. Biologically speaking, avocados, bananas, and even watermelons are technically berries, but to simplify things, I use the colloquial term for any small edible fruit. So, this category includes kumquats, grapes, raisins, and fruits that are typically thought of as berries even though they technically aren’t, like blackberries, cherries, mulberries, raspberries, and strawberries. 

For Other Fruits, a serving is a medium-sized fruit, a cup of cut-up fruit, or a quarter cup of dried fruit, and I recommend at least three daily servings. Again, I’m using the colloquial rather than the botanical definition, which is why I put tomatoes in the Other Vegetables group. 

Cruciferous Vegetables include broccoli, cabbage, cauliflower, Brussels sprouts, collards, and kale, and I recommend at least one half-cup serving a day. My Daily Dozen also calls for at least two additional daily servings of Greens, cruciferous or otherwise, and two serving of Other Vegetables, with a serving being a cup of raw leafy vegetables, a half cup for raw or cooked non-leafy vegetables, and a quarter cup of dried mushrooms. 

Everyone should try to incorporate one tablespoon of ground Flaxseeds into their daily diet, in addition to one serving of Nuts and Seeds. A quarter cup of nuts is considered a serving, or you can have two tablespoons of nut or seed butters, including peanut butter. Chestnuts and coconuts don’t count nutritionally as nuts.  

For my Herbs and Spices category, I recommend a quarter teaspoon a day of the spice turmeric, along with any other salt-free herbs and spices you may enjoy.  

To meet my Daily Dozen, you need at least three servings of Whole Grains, and a serving can be a half cup of hot cereal (like oatmeal), cooked whole grains or so-called pseudograins (like amaranth, buckwheat, and quinoa), cooked pasta, or corn kernels; a cup of ready-to-eat cold cereal; one tortilla or slice of bread; half a bagel or english muffin, or three cups of air-popped popcorn. 

The serving size in the Beverage category is one 12-ounce glass, and I recommend at least five servings a day in addition to the water you get naturally from the foods in your diet. If you’re curious, I explain my rationale in my How Many Glasses of Water Should We Drink a Day? video.

Finally, my Daily Dozen calls for at least one daily “serving” of exercise, which can be split up over the day. I recommend 90 minutes of moderate-intensity activity, such as walking briskly (for instance, at a pace of four miles per hour), or 40 minutes of vigorous activity, like jogging or active sports. See my video How Much Should You Exercise? if you’d like more information. 

This may sound like a lot of boxes to check, but it’s easy to knock off a bunch at a time. One simple peanut butter and banana sandwich on whole-grain bread can check off four boxes, and imagine how many Daily Dozen boxes you could tick off when you sit down to a big salad of two cups of spinach, a handful of arugula, a handful of walnuts, a half cup of chickpeas, a half cup of red bell pepper, and a small tomato. That’s seven boxes in just one salad! Sprinkle on your flaxseeds, add a handful of goji berries, enjoy it with a glass of water, and end with some fruit for dessert, and you just met nearly half of the Daily Dozen in a single meal! And, if you just ate it on your treadmill…just kidding! 

Do I check off each glass of water I drink? No. In fact, I don’t even use the checklist anymore. I just used it initially as a tool to get me into a routine. Whenever I sat down to a meal, I challenged myself by asking, Could I add greens to this? Could I add beans to this? Can I sprinkle on some flax or pumpkin seeds? What about some dried fruit? The checklist just got me into the habit of wondering how I can make each meal even healthier. 

The checklist also helped with grocery shopping. Although I always keep bags of frozen berries and greens in the freezer, if I’m at the store and want to buy fresh produce for the week, it helps me figure out how much kale or blueberries I need. 

In fact, the checklist even helped me picture what a meal might look like. When you look over the Daily Dozen, as you can see at 6:44 in my video, you see that it includes three servings each of Beans, Other Fruits, and Whole Grains, and about twice as many vegetables in total than any other component, when you add up the Cruciferous Vegetables, Greens, and Other Vegetables. So, glancing at my plate, I can imagine one quarter of it filled with grains, one quarter with legumes, and vegetables taking up the other half, along with a side salad and fruit for dessert, for instance. I really like one-bowl meals where everything’s mixed together, and even then the checklist helps me visualize. Instead of a big bowl of spaghetti with some veggies and lentils on top, I think of a big bowl of vegetables with some pasta and lentils mixed in. Instead of a big plate of quinoa with some stir-fried vegetables, I picture a meal that’s mostly vegetables with some quinoa and beans added in there, too. 

There’s no need to be obsessive about the Daily Dozen. On hectic travel days, when I’ve burned through my snacks and find myself stuck in some airport food court, I’m lucky if I hit even a quarter of my goals.  

If you eat poorly one day, just try to eat better the next. 

To help track your progress, volunteers created Dr. Greger’s Daily Dozen apps for both iPhone and Android. You can download and use them both for free with no ads and no cost. 

My hope is that the checklist will serve as a helpful reminder to try to eat a variety of some the healthiest foods every day. 


  • All plant foods are not created equal, so although we should try to center our diets around whole plant foods, we should be sure to incorporate the most healthful ones.
  • Some of the most special and important nutrients are sulforaphane, which is found almost exclusively in cruciferous vegetables, and flaxseeds with their anticancer lignan compounds.
  • The Daily Dozen checklist is the synopsis of recommendations I make in my book How Not to Die, incorporating everything I try to fit into my daily routine and lists categories and minimum servings.
  • My Daily Dozen includes Beans (and legumes, including split peas, chickpeas, and lentils), Berries, Other Fruits, Cruciferous Vegetables, Greens, Other Vegetables, Flaxseeds, Nuts and Seeds, Herbs and Spices, Whole Grains, Beverages, and Exercise.
  • The Daily Dozen is intended to inspire you to eat more healthful options and look at each eating experience as an opportunity to maximize nutrition.
  • To help you tick the Daily Dozen boxes, volunteers created Dr. Greger’s Daily Dozen app, completely free to download and use, and available for both iPhone and Android.

This was quite the departure from our regular blogs! Normally, we just share the science from the primary sources in the peer-reviewed medical literature, but I want to be more than just a reference site. I want it to be a practical guide on translating this mountain of data into day-to-day decisions, which is where my Daily Dozen app slips into the mix. It’s available for free on iTunes and as an Android app, thanks to an amazing group of volunteers through our Open Source Initiative

For more introductory-type videos, check out: 

How can you actually incorporate those Daily Dozen foods into your diet? Check out my How Not to Die Cookbook. If you didn’t already know, all the proceeds I receive from that—and all my books, in fact—go to charity. 

In health, 

Michael Greger, M.D. 

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations: 

The Dangers of Oil Pulling 

Tue, 07/27/2021 - 07:00

In my previous articles on oil pulling, I discussed how the ancient practice may be no more effective than swishing with plain water for plaque and gingivitis, doesn’t whiten your teeth, and may even worsen dental erosion.

What about oil pulling to treat tooth sensitivity? About a quarter of people have sensitive teeth, for example, experiencing aching sensations when drinking ice water. So researchers split people into three groups—oil pulling, desensitizing toothpaste, and placebo just rinsing with saltwater—and then blasted the subjects’ teeth with cold air. As you can see at 0:44 in my video The Risks of Oil Pulling, the placebo didn’t help much; the before-and-after sensitivity scores were the same for nine out ten in the placebo group. The desensitizing toothpaste, however, seemed to help most of the patients, as did the oil pulling. Okay, so there is some benefit to oil pulling. If you have sensitive teeth, why not give it a try? Unless, of course, there are some downsides or risks associated with oil pulling.

Typically, the only concerns you see expressed are for clogging your sink drain, but the reason it’s warned against in young children is fear of aspiration. The kids could accidentally choke on the oil, causing some to go down the wrong pipe into their lungs. Actually, this could happen at any age, but is this just a theoretical concern? No. Attributed to oil pulling are cases of lipoid pneumonia, which is when you get an oily substance stuck down in your lungs.

This was first described in 1925, when it was customary to use substances like mentholated Vaseline in the nostrils of kids—until they died of pneumonia. On autopsy, areas of their lungs were found to be clogged with an oily fluid. Glad we don’t use mentholated Vaseline anymore? But we do. That’s what Vicks VapoRub is, and if you stick it in your nostrils, you can end up filling up part of your lungs with it, as you can see at 2:18 in my video. Vaseline liquefies at body temperature and creeps down into your lungs as you sleep, which is why you should never put it in your nose before bedtime. People need to be aware of this. Ages ago, I did my part by posting the video Is Petroleum Jelly Good for You?. It’s not just Vaseline, though—anything oily or greasy can do it. For instance, evidently, an “intranasal butter application” was an old folk remedy given to kids with a stuffy nose. Unfortunately, the kids could end up with pneumonia or a stuffy lung.

The same thing can happen with olive oil. There was even a case of a woman who contracted lipid pneumonia because she mistakenly thought it was a good idea to put baby oil in her nose when her nostrils were dry. Less common causes include inhaling too much vaporized candle wax, after spending most of your time in a shrine surrounded by burning candles, for instance. Lipoid pneumonia isn’t nicknamed “fire-eater’s lung” for nothing, as performers place themselves at risk for aspirating tiki torch oil in their act. Thankfully, one really uncommon cause is self-injection with oil. Why would anyone do that? To “increase the size of [their] genitals,” of course, until they accidentally hit a vein and squirt oil into their bloodstream.

As bad as that is, I’m more concerned about cases like this: A woman was admitted to the hospital for pneumonia four times in just six months. “During the fourth admission, [her doctors] meticulously inquired about every possible cause of her recurrent pneumonia, and she revealed that she had been oil pulling 2 weeks prior to her first admission.” Then, after she was discharged from the hospital, “she returned to the practice even more rigorously to remove any possible toxic effects of medicines she had taken during his hospitalization.” Her attempt to “detoxify” from all the drugs they had given her led to three more hospital admissions. Her doctors told her to stop the oil pulling, and no more pneumonia.

That’s one of the reasons the American Dental Association recommends against the practice. In fact, you may remember the tooth-whitening experiment I discussed in a previous article. The researchers used extracted teeth instead of actual real-life human subjects. Why? They stated that “it was not ethically sound to conduct a human trial of…this [oil pulling] practice with the knowledge that there was a chance of inducing lipoid pneumonia in study volunteers.”

This article discusses the final video in my four-part series on oil pulling. For the first three, see:

Speaking of toothpaste, have you ever wondered about that ingredient SLS? Check out my videos Is Sodium Lauryl Sulfate Safe? and Is CAPD in SLS-Free Toothpaste Any Better?.

For more on dental health, see:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations:

Check Out My Daily Dozen Resources

Thu, 07/22/2021 - 07:00

By now, you are probably familiar with my Daily Dozen checklist, a simple tracker that can help you get into the habit of including some of the healthiest of healthy foods and exercise into your everyday routine. But, if you need some extra support and inspiration to get those boxes checked off, join our free Daily Dozen Digest—an 11-week email series full of facts and recipes, all to help you on your health journey. Watch our new video about the Daily Dozen app below, and sign up here for the free Digest.

  Donations Matched!

One of our amazing supporters, Janet Bruce, will match all donations using this form for up to a total of $15,000!

Double your impact by making a donation to today…and thank you for your support!



  Key Takeaways: Smoothies 

Smoothies can either be filled with dairy and sugar or be made with some of the healthiest foods on the planet. What does the science say about them? Is there anything we need to be cautious about? Check out the smoothie topic page for a full summary, as well as my videos. (I even have a video where I make my own smoothie recipe!)




Recipe: Barley Tabbouli Salad with Tahini Drizzle

Intact barley stands in for cracked bulgur in this hearty salad, but you can use another whole grain if you prefer. This recipe is a great way to make use of any leftover cooked whole grains you may have on hand. A drizzle of tahini sauce adds a unique depth of flavor to the salad. You can find the full recipe here and a video of how it’s made here.




PAN Is Hiring

One of my favorite organizations, Physicans Association for Nutrition, is looking for a whole food, plant-based nutrition expert for the position of Medical Content Executive. The position is fully remote, and candidates can be based anywhere in the EU, Africa, or USA (east coast). Go here for more information and to apply.




Spotlight Volunteer: João Madureira

I have been doing Portuguese translations for a few years. I love doing it, because it has a real impact on the health of so many people and the planet. The work of is very important for many reasons. One of the major reasons, in my view, is that it sharpens critical thinking and shows the biases that exist even in scientific work.

My favorite whole food, plant-based dish is curry. I love to put a lot of antioxidant-rich spices in it, and I replace the oil with tomato paste and ground flaxseed.




What Causes Cancer to Metastasize?
Palmitic acid, a saturated fat concentrated in meat and dairy, can boost the metastatic potential of cancer cells through the fat receptor CD36.



The Benefits of Moringa: Is It the Most Nutritious Superfood?
Does the so-called miracle tree live up to the hype?




Flashback Friday: Eating More to Weigh Less

Energy density explains how a study can show participants lose an average of 17 pounds within 21 days while eating a greater quantity of food.


Next Live Q&A on July 22

Every other month, I do a live Q&A directly from my treadmill, and Thursday, July 22 is the day.

Join on our Facebook page or YouTube channel at 3pm ET. I’ll be streaming to both at the same time!

You can find links to past live Q&A’s here on If that’s not enough, don’t forget I have an audio podcast to keep you company, too.

And check out my recent dualing-treadmills interview with The Jaroudi Family.


In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:

Oil Pulling May Worsen Dental Erosion

Tue, 07/20/2021 - 07:00

A review of the effects of oil pulling concluded that, indeed, the ancient practice “may have beneficial effects on oro dental hygiene,” or oral and dental health. I’ve talked before about studies investigating oil pulling and dental health, but what about oral health? That’s the subject of my video Oil Pulling for Teeth Whitening and Bad Breath Tested.

Oil pulling was also tested against oral malodor, also known as halitosis or, simply, bad breath. It’s believed a quarter of the world’s population suffers from it, so researchers decided to put oil pulling versus chlorhexidine to the test, but how do you test for bad breath? There are all sorts of really fancy methods, such as “gas chromatography electronic nose, diamond probes, dark field microscopy,” but they are really expensive or not very reliable. So, the researchers decided to go with the “gold standard”: Study subjects were told to just breathe into the examiner’s face.

The researchers also wanted to know what the subjects thought about their own breath, so they instructed them to lick their own wrist, sniff it after it had dried, and then give the smell a score from zero (no odor present) to five (extremely foul odor). Though the subjects themselves thought their licked wrists smelled better after two weeks of oil pulling, the researchers disagreed that their breath smelled any better. You can see the scores at 1:07 in my video.

After three weeks, however, there was a significant and comparable improvement in breath odor in both the oil pulling and chlorhexidine groups. I was excited about this study, because the researchers used an actual placebo—colored water, in this case—presumably to match the look of the chlorhexidine and also had the subjects swish for the same duration. Finally! At last, we can answer that nagging question as to whether plaque and gingivitis improves with oil pulling because of the oil, or just because swishing anything in your mouth for that long will make a difference. In fact, as you can see at 1:50 in my video, the water worked just as well. The researchers saw the same drop whether the test subjects swished with oil or swished with plain water, suggesting that the plaque is simply disrupted by the extended “rinsing action.” Yes, oil may be five to six times cheaper than chlorhexidine and safer, too, but water is cheaper and safer than both.

But can water whiten teeth? Numerous websites offer testimonials of oil pulling whitening teeth, but with no studies published in the medical literature, most doctors would just give up there. Not all doctors, though. Two dental professors in Detroit decided to put it to the test. “Teeth were selected from a stored collection of human extracted teeth”—sounds a little horror movie-ish—and then put into tubes with coconut oil, sesame oil, or sunflower oil, along with some fake saliva. The professors vigorously shook the tubes every day for two weeks. The result? No evidence to suggest that oil pulling has any effect on teeth whitening.

Another internet darling—“DIY whitening consist[ing] of a strawberry and baking soda mix,” which was evidently featured on Dr. Oz—had a similar outcome when put to the test. Over-the-counter whitening strips worked, a home whitening system in which the dentist sends you away with custom trays also worked, as did in-office tooth whitening, but the DIY strawberry and baking soda mixture failed. It was as bad as plain water, which had been used as a control. You can see the results at 3:05 in my video.

What about dental erosion? In my video Plant-Based Diets: Dental Health, I talked about how those eating more healthfully may have healthier gums, but since they tend to consume more acidic food and drink like citrus, tomatoes, and fruity teas, they may be at greater risk of eroding some of their enamel, which is why we should all rinse our mouth with water after eating or drinking anything acidic or sour. What about rinsing with oil every morning? The way our body protects against dental erosion is by forming a “pellicle”—a protective layer of mostly proteins from our saliva and some fat—over our teeth. Might oil pulling help prevent erosive damage to our tooth surfaces by, in a way, buttressing this protective layer? You don’t know until you put it to the test.

The researchers wanted to put the teeth under a microscope afterwards, but that’s hard to do when the teeth are still in people’s heads. So, they put slabs of cow’s teeth in the subjects’ mouths, let them sit there until that protective layer developed, and then oil pulled around the teeth—or not, in the control group—and then took them out and exposed them to acid.

As you can see at 4:43 in my video, if you expose the teeth to acid without putting them in your mouth, within two minutes, 120 seconds, significant demineralization takes place. Calcium is dissolved out of the teeth by the acid. But, if you let those same teeth sit in your mouth for a few minutes before exposing them to acid, there’s less erosion. What happens if you then put them back into your mouth and do some oil pulling? Is there even less erosion? No, there’s more. It’s as if the oil pulling undermined the protective layer. Indeed, that’s exactly what the researchers saw under the microscope, as you can see yourself at 5:20 in my video. The researchers suspect the oil may actually be depleting the pellicle, “impairing its protective properties.”

This article discusses the third video in a four-part series on oil pulling. If you missed the first two, see Does Oil Pulling Help with Cancer? and Oil Pulling Benefits for Plaque and Gingivitis.

For the final video of this series and the final nail in the coffin of oil pulling, see The Risks of Oil Pulling.

How can we protect our enamel? See:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations:

Does Oil Pulling Help Dental Plaque or Gingivitis?

Thu, 07/15/2021 - 07:00

Oil pulling is put to the test head-to-head against chlorhexidine mouthwash for oral and dental health measures. 

What are the potential risks and benefits of the ancient practice of oil pulling, in which oil is swished or “pulled” between the teeth for 15 minutes or so and then spit out? There are wild, unsubstantiated claims online and even in the medical literature, including the British Dental Journal. I can believe oil pulling is good exercise for your tongue and cheek muscles, but it seems a little crazy to suggest “it heals cells, tissue and all organs simultaneously.” Talk about tongue in cheek!  

A respondent in the British Dental Journal expressed “surprise” in reading that “swishing…oil around the mouth…can ‘effectively treat … meningitis, heart and kidney disorders, women’s hormonal disorders, and chronic diseases like cancer, AIDS etc.’” It’s certainly possible that oil pulling may help in some way, but in order to enter into evidence-based medicine, we need a little something called evidence “without being distracted by illusory effects ascribed to them by their advocates.” This is particularly relevant when other respondents shared their experience of a case of severe inflammatory gingivitis that worsened after oil pulling. After the subject stopped oil pulling, however, her gingival inflammation got better. The researchers felt some of the oil had gotten stuck under her gums, worsening her condition. Regardless, perhaps people should hold off on oil pulling until we actually have some evidence.  

Thankfully, as I discuss in my video Oil Pulling Benefits for Plaque and Gingivitis, the Centre for Evidence-Based Medicine at Oxford recently compiled all of the controlled trials. Controlled? Why is it so important for studies to have control groups? Without a control group against whom to compare findings, it may be the case that reported declines in gingivitis and plaques with oil pulling are simply due to the fact that the subjects had dentists looking over their shoulders and faced recurring check-ups, so they may have just upped their brushing and flossing game. 

At 1:52 in my video, I present the kind of study we need. Researchers observed no changes before and after in the control group, but there was a drop in plaque and gingivitis scores in the oil-pulling group. That’s more like it! Okay, so there does seem to be an effect, but what do those scores mean? When you test a new drug, it isn’t enough just to show it works better than nothing, or better than a sugar pill. Ideally, you want to know whether the new drug works better than the current best drug out there for the same condition. Otherwise, what’s the point of a new therapy? This is why drug companies are often forced to use so-called active controls, comparing their drug head-to-head against the leading drug instead of pitting it against a placebo. In the study I just mentioned, oil pulling was compared to doing nothing. How about oil pulling compared to chlorhexidine?  

An antiseptic chemical used in medicated mouthwash, chlorhexidine is considered to be the “gold standard” in the fight against plaque, cavities, and gingivitis. Talk about a head-to-head battle! What happened when researchers investigated oil pulling against chlorhexidine, measuring each treatment’s ability to lower the number of cavity-producing bacteria on people’s teeth? As you can see at 3:07 in my video, researchers found that chlorhexidine worked faster, resulting in a significant drop in plaque within just 24 hours, whereas it took a week for the oil pulling to really start working. By two weeks, though, the oil pulling may end up just as efficacious as the gold standard, as you can see at 3:18 in my video. In fact, they appeared to work so similarly that the skeptic in me wondered, Wait a second. Maybe it’s just the physical act of swishing that disrupts the plaque

If only the researchers had included a third group who swished with plain water. They did! And? Swishing with water had no effect. 

Now, it wasn’t exactly fair. The researchers had the oil-pulling group swish for ten minutes, whereas the other two groups only swished for one minute. So, for all we know, swishing with plain water for ten minutes might be as good as swishing with oil.  

What’s more, one could look at this and argue that chlorhexidine actually worked ten times better than oil because it got the same effect swishing for one-tenth of the time. Chlorhexidine has side-effects, though. In fact, it has potentially serious side effects, like painful desquamation, meaning peeling of the mucous membranes in your mouth, as well as discoloration of the teeth or tongue, which you can see at 4:11 in my video (but be warned because they aren’t pretty sights). 

So, “oil pulling has certain benefits over commercially available mouthrinses such as non-chemical, non-alcoholic, low cost, and non-staining, yet the effectiveness…[is] unclear.” Hold on. Oil pulling has been shown to significantly drop the number of cavity-causing bacteria on the teeth. Yes, but does that translate out into fewer actual cavities, which is what we really care about? It hasn’t been studied. Researchers did pair up oil pulling versus chlorhexidine against plaque and gingivitis, however, and found both were able to help to a similar degree. And, plaque-induced gingivitis is a reasonable predictor of future dental health, thereby explaining Oxford’s Centre for Evidence-Based Medicine’s conclusion that, indeed, “oil pulling may have beneficial effects” on oral and dental health. 


  • The ancient practice of oil pulling, swishing or “pulling” edible oil between the teeth before spitting it out, has been said to be an effective treatment for meningitis, heart and kidney disorders, and such chronic diseases as cancer and AIDS, without any scientific evidence.
  • Chlorhexidine, an antiseptic chemical used in medicated mouthwash, is considered to be the gold standard in the fight against plaque, cavities, and gingivitis, yet has potentially serious side effects, including painful peeling of your mouth’s mucous membranes.
  • When oil pulling was pitted head-to-head against chlorhexidine, researchers found that although chlorhexidine worked faster than oil pulling in reducing plaque, by two weeks, the oil pulling may be just as effective as the antiseptic chemical.
  • The act of swishing alone may have caused the plaque disruption, however the oil-pulling group swished for ten minutes compared with only one minute for the chlorhexidine and water-only groups, so we cannot know for certain if swishing with plain water for ten minutes might be as effective as swishing with oil.
  • Unlike chlorhexidine, oil pulling is free of chemicals and alcohol, as well as lower in cost, and it appears to be similarly effective as the antiseptic against plaque and gingivitis.

This article discusses the second video in a four-part series on oil pulling. If you missed the first video, see Does Oil Pulling Help with Cancer?

Oil Pulling for Teeth Whitening and Bad Breath Tested is the third in the series. 

I do not recommend oil pulling and explain why in the final video of the series, The Risks of Oil Pulling

For other tips on oral and dental health, see: 

In health, 

Michael Greger, M.D. 

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations: 


Oil Pulling for Cancer? 

Tue, 07/13/2021 - 07:00

What evidence exists to suggest oil pulling can effectively treat serious diseases, such as paralysis, meningitis, cancer, and AIDS? 

I’ve produced videos on how coconut oil is safe to put on your hair or put on your skin, but you certainly don’t want to eat it. In fact, you may not even want to be in the same kitchen when coconut oil is being heated. I don’t know where people got the idea it’s safe to use for cooking. Coconut oil has one of the lowest smoke points. It can release a variety of toxic compounds at typical frying temperatures, and “emissions below the smoke point…might be harmful,” so you want to make sure there is good ventilation.  

Don’t inject it into your privates, and even standing under a coconut tree is not completely without risk. But, what about swishing coconut oil around in your mouth? Evidently, so-called “oil pulling…is a time-honored…folk remedy that involves swishing edible oil in the mouth”—that is, “pulling” it back and forth between the teeth for purported “oral and systemic health benefits.” You put a spoonful of oil in your mouth and swish it around for up to 20 minutes. If that’s too long, you can “pull” for just 5 or 10 minutes. Then, spit it out, rinse out your mouth, and brush your teeth.  

I could see how oil pulling might, for example, dislodge dental plaque and have some oral health benefits, but systemic effects? As I discuss in my video Does Oil Pulling Help with Cancer, not only is it supposedly “absolutely harmless,” but apparently “this simple method makes it possible to effectively treat the most varied diseases, in some cases enabling one to avoid surgical intervention and the taking of medications that can have harmful side effects.” I was excited to check out a citation within a review on oil pulling, until I realized the source was, an e-book that evidently provides answers to questions like “oil for oil pulling [sic], pulling oil and diseases cured and the science behind oil pulling therapy [sic] and much more.” 

The moral of the story? Always check your sources. 

One source cited by oil-pulling proponents does seems legitimate, though. It was published in the British Dental Journal, but it’s just a letter from some guy saying the literature has reported that oil pulling can “effectively treat various disorders like…paralysis…meningitis…and chronic diseases like cancer, AIDS etc.” However, absolutely no references are given. So, this literature of which he speaks is presumably the fairy tale literature. The bottom line is that there is simply no scientific proof to these claims.  

What about the oral health claims? If you look at the list of purported benefits, from blood clots to stopping the growth of malignant tumors, and check out the citations purported to back up such wild statements, at this point, you probably won’t be surprised to find they have absolutely nothing to do with blood clots, cancer, or any of those other diseases. Instead, they are references to studies done on dental health. Well, let’s not spit the baby out with the bathwater. Let’s see what they say. 

The studies start out like this: Add oil pulling to some people’s regular oral hygiene regimens, then stand back and watch gingivitis get better week after week, as the amount of plaque gets less and less, as you can see at 3:21 in my video. That study used sunflower oil. The finding? “Conclusion: Oil pulling is having dental benefits.” The same was found with coconut oil, as you can see at 3:35 in my video. Gingivitis and gum inflammation started to get better within a week, as the dental plaque went down. Sounds pretty good, right? So, the researchers came to a similar conclusion: “Oil pulling…could be an effective adjuvant procedure in decreasing plaque formation and plaque induced gingivitis,” a useful addition to one’s oral hygiene habits. 

Anyone see what’s wrong with these studies? There was no control group.  

Why am I always going on and on about needing control groups? Didn’t the studies act as their own control? Think about it: We know where the subjects were at baseline, and then week after week, we saw their plaque and gingivitis get better and better. Are we supposed to imagine it’s all just one big coincidence that all of the subjects just happened to start getting better right after they started the coconut oil? 

Let me tell you about a phenomenon termed the Hawthorne Effect. “Patients frequently appear to improve merely from the effects of being placed in a clinical trial.” Why? Because “patients may improve oral hygiene…as a result of the special attention or frequent examinations that often result from study participation.” Indeed, the Hawthorne Effect is why it’s so important to do controlled trials. 

It happens to the best of us. You know how you may brush extra thoroughly the morning of a dentist appointment? Well, imagine knowing you’ll be going back to the dentist for an exam every single week for a month to check on your plaque and gingivitis. Don’t you think you’d brush a little more and floss a little more? That uptick in oral hygiene alone could get you the kinds of results seen in these studies. So, the only way to tell if oil pulling had anything to do the improvements is to have a control group who didn’t do the oil pulling but also knew they would be getting weekly dental checkups. Unfortunately, there weren’t any compilations of controlled studies… until the study I cover in my video Oil Pulling Benefits for Plaque and Gingivitis


  • Coconut oil may be safe for use on your hair or skin, but I do not recommend consuming it or even being in the vicinity when it is being heated as it can release toxic compounds at typical frying temperatures and emissions may be harmful.
  • Oil pulling—swishing edible oil and “pulling” it between the teeth—is a folk remedy, but there is no scientific proof to claims it is effective for cancer, paralysis, meningitis, blood clots, AIDS, or other chronic diseases.
  • When adding oil pulling to regular oral hygiene practices, the amount of plaque seems to diminish, and gingivitis and gum inflammation may improve, but such studies were conducted without a control group so the results remain unfounded.
  • The Hawthorne Effect, wherein subjects appear to achieve benefits simply because of their involvement in a clinical trial, may be at play. For example, participants may improve oral hygiene practices as a result of the increased scrutiny or more frequent exams resulting from the study, and that increase itself could be the cause of perceived improvements.

This article discusses the first video in a four-part series on oil pulling. For the rest of the series, see:  

I delved into oil pulling because people kept asking me about it. What other health topics, nutrition-related or not, do you want me to take on? 

Why did I say not to swallow coconut oil? See: 

What can one do for cancer? Check out How Not to Die from Cancer, my overview video. 

In health, 

Michael Greger, M.D. 

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations: 


Fasting for Weight Loss Infographic

Thu, 07/08/2021 - 07:00

Fasting has been branded the “next big weight loss fad,” and about one in seven Americans report using some sort of fasting as a means for weight loss.

This infographic is a guide to explore some of the key facts to help you to make your own choice. Dr. Greger compares the advantages and disadvantages of different types of fasting based on the latest evidence, and provides some important cautions and notes to consider before deciding to start.

For all of the videos on fasting, check out our topic page. Fasting for weight loss is also covered in-depth in Dr. Greger’s book How Not to Diet.

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations: