Is Nutritional Yeast Healthy for Everyone?

Those with certain autoimmune diseases such as Crohn’s disease should probably not eat nutritional yeast.

Thousands of years ago, some yeast floated down into our flour and drinks, pleasing our palates, and we’ve been regularly exposed to it ever since. Yeast isn’t a problem for most people, but even non-disease-causing microbes could potentially trigger autoimmune diseases like Crohn’s disease in those who are susceptible because their finely tuned immune balance is somehow off. Maybe that’s why bakers have the highest Crohn’s disease mortality and, from a different data set, also have among the highest rates of Crohn’s disease, as you can see at 0:30 in my video Is Nutritional Yeast Healthy for Everyone? Perhaps a “hypersensitivity to baker’s yeast…may play a role in Crohn’s disease.”

If you take people with Crohn’s and remove from their diets the three foods to which they appear to have the most antibodies, in order to try to calm their disease, and then add those foods back, you can provoke the symptoms once again and re-stimulate the inflammation. So, for example, an anal fistula gets nice and dry off those foods, starts oozing again once the foods are back in the diet, and then the spigot’s turned back off when the foods are removed once more, as you can see (ew!) at 0:57 in my video.

However, without a control group, you can’t exclude the possibility of a powerful placebo effect. There hadn’t been any such randomized controlled trials until researchers came up with a brilliant design. They tested people with Crohn’s for antibodies to 16 different foods and then randomized the subjects into two groups. Both groups were told to avoid four foods, but one group was told to avoid the four foods they reacted most to, while the other group was told to avoid the foods they reacted least to. The group assignments were given in sealed envelopes, so no one knew who was in which group until the end. So, did it matter? Yes, more than twice the probability of major clinical improvement was seen in the group told to stay away from the four foods their blood reacted most to—but that wasn’t just yeast. In fact, the “exclusion of milk, pork, beef, and egg was most strongly associated with improvement,” leading the researchers to suggest that perhaps instead of doing fancy blood tests, we should just tell our patients to cut out meat and eggs and see how they do. This would be consistent with population studies that associate “diets high in animal fat” with an increased risk of inflammatory bowel diseases, as well as interventional studies showing that a plant-based diet, in which meat is cut down to about one serving every two weeks, can drop relapse rates as low as an extraordinary 8 percent over two years.

But, what about the whole yeast question? Can’t you just put some yeast up someone’s butt and see what happens? Why, yes! Yes, you can, and researchers have. Indeed, researchers tested rectal exposure to six different foods, including yeast, in Crohn’s disease patients. This was kind of like a skin prick test, but instead of pricking the skin, they pricked the inside of people’s rectums with various foods. You can see at 3:00 in my video the various prick sites for the different foods, and it’s clear that yeast gave the most significant reaction in Crohn’s patients.

It appears that baker’s yeast, which is the same yeast as brewer’s yeast and nutritional yeast, may indeed have disease-causing importance in Crohn’s disease, but the good news would then be that it “may be of therapeutic relevance.” If Crohn’s patients went on a yeast-free diet, would they feel better? You don’t know until you put it to the test.

In fact, that’s exactly what the original study linking yeast and Crohn’s disease suggested back in 1988. “A controlled trial of a yeast free diet for patients with Crohn’s disease may therefore be worth while.” Why did it take years before such a study was done? Well, who’s going to fund it? Big Soda Bread? Thankfully, there are charities like the National Association for Colitis and Crohn’s disease, willing to put up the (yeast-free) dough.

Nineteen patients with Crohn’s disease ate their regular diet for a month and were then switched to a yeast-exclusion diet. There was a significantly higher CDAI, Crohn’s Disease Activity Index, which assesses symptoms like abdominal pain and diarrhea, during the period when they were eating yeast, compared to the yeast-free period. So, there was worse disease activity with yeast than without. Okay, but what was this yeast-free diet? They didn’t just cut out bread and beer. The researchers switched people from dairy milk to soy milk and from white flour to whole wheat, for example. Just cutting out milk can sometimes help with inflammatory bowel disease, as you can see at 4:43 in my video.

So, with so many dietary changes, how do we know what role the yeast played? This is how we know what role the yeast played: After placing the subjects on the new yeast-free diet, they then challenged the Crohn’s sufferers with either a capsule of yeast or a placebo. A tiny amount of yeast, like giving them a quarter teaspoon of nutritional yeast a day, made them worse, suggesting “yeast may be important in the pathogenesis [disease process] of Crohn’s disease.”

Now, for the vast majority of people, yeast is not a problem, but in susceptible individuals, it may trigger an abnormal immune response in the gut. But, wait. I thought the paratuberculosis bug was considered a trigger for Crohn’s disease. Well, maybe infection with paraTB is what “induces a hypersensitivity response to dietary yeast.” Who knows? The bottom line is that people with Crohn’s disease should not go out of their way to add baker’s, brewer’s, or nutritional yeast to their diets.

I introduced this topic in Does Nutritional Yeast Trigger Crohn’s Disease?, then took a bit of a tangent with Is Candida Syndrome Real?. Next, I finish up this video series by talking about another autoimmune disease that appears to be affected: Dietary Cure for Hidradenitis Suppurativa.


For more on Crohn’s, see Preventing Crohn’s Disease with Diet and Dietary Treatment of Crohn’s Disease

And paratubercuwhat? See Does Paratuberculosis in Milk Trigger Type 1 Diabetes? and Does Paratuberculosis in Meat Trigger Type 1 Diabetes?

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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:

Treating Advanced Prostate Cancer with Diet

Dr. Dean Ornish showed that a plant-based diet and lifestyle program could apparently reverse the progression of prostate cancer for early stage, localized, watch-and-wait cancer. What about for more advanced stage life-threatening disease?

Dr. Dean Ornish showed that a plant-based diet and lifestyle program could apparently reverse the progression of prostate cancer by making men’s bloodstreams nearly eight times better at suppressing cancer cell growth. But this was for early-stage, localized, watch-and-wait prostate cancer.

What about for more advanced-stage, life-threatening disease? There have been sporadic case reports in the literature suggesting benefit. For example, a man with extensive metastatic disease who had been given about three years to live went on a strict plant-based diet. Four years later, it appeared the cancer had disappeared. After six years, he got a little too comfortable, backslid a bit on the diet and began eating “turkey, tuna fish, and chicken,” then the cancer came raging back and he died. But that could have been a total coincidence. That’s the problem with case reports, which are kind of glorified anecdotes. You have no idea how representative the outcome is unless it’s studied formally. But, throughout the 20th century, all we had were these kinds of case reports for more advanced prostate cancer until 2001.

We had “preliminary evidence” based on all the case reports that “prostate cancer may be sensitive to diet even after metastasis develops. Plant-based diets may be associated with prolonged survival and instances of remission of bone metastasis in men with advanced disease.” So, researchers decided to put it to the test in a four-month intervention. They thought that too much saturated fat, too little fiber, and too much meat may be the biggest players in tumor promotion and progression, so they put people on a whole food plant-based diet of whole grains, beans, seeds, and fruits. Figuring this would be quite the departure from their regular diet, the researchers included a stress reduction component in hopes of improving dietary compliance.

Who were the subjects? The ten men in the study didn’t just have prostate cancer—they had all undergone a radical prostatectomy to remove their primary tumor and then subsequently had increasing PSA levels, indicative of probable metastatic disease. PSA stands for prostate-specific antigen. It’s only made by prostate cells, but the ten men had just had their entire prostates removed so their levels should have been zero. The fact that they not only still had some PSA, but that it was rising suggests that the surgery had failed, and the cancer had spread and was making a comeback.

At 2:43 in my video Treating Advanced Prostate Cancer with Diet: Part 1, you can view a graph showing the PSA levels for each of the men before the study began and see the speed at which their PSAs went up. If their PSA trajectories had stayed the same after four months of eating healthfully, it would mean the diet had had no effect. In that case, presumably, the cancer would have still been powering away and spreading just as fast as before. Instead, in two of the men, it looked as if the cancer had accelerated and grew even faster, but in the other eight men, the intervention appeared to work, apparently slowing down cancer growth. And, in three of the ten men, it didn’t just slow or stop, but appeared to reverse and shrink.

Why the different responses? Well, in the Ornish study, the more people complied with the diet and lifestyle recommendations, the better they did, as you can see at 3:31 in my video. Dietary changes only work if you actually do them. Just because you tell people to start eating a whole food plant-based diet, doesn’t mean patients actually do it. One can use fiber intake as a proxy for dietary compliance because all whole plant foods have fiber, and Ornish’s patients about doubled their fiber intake from 31 grams to 59 grams.

How did the ten men in the 2001 study do? They started out even worse, averaging 14 grams of fiber a day, and only made it up to 19 grams a day. That’s not a whole food plant-based diet—that doesn’t even meet the recommended minimum daily intake. As you can see at 4:18 in my video, only four of the ten men even increased their fiber intake at all, so that may explain the different responses. In fact, the man whose fiber improved the most had the best PSA result, and the man whose fiber intake dropped the most had the worst PSA result. Indeed, it appears the more changes they made to their diet, the better their results.

The researchers concluded that “a plant-based diet delivered in the context of MBSR [Mindfulness-Based Stress Reduction]…may slow the rate of tumor progression,” and, unlike other treatments, may give patients some control over their disease. And, as Ornish pointed out, “the only side effects are beneficial ones.”

Dr. Ornish and colleagues were able to show an apparent reversal in the progression of early-stage, localized prostate cancer with a plant-based diet and lifestyle program, and researchers at the University of Massachusetts and elsewhere showed a similar diet may help slow the progression of even advanced prostate cancer over a period of four months.

How about over six months? As I discuss in my video Treating Advanced Prostate Cancer with Diet: Part 2, researchers at University of California, San Diego put cancer patients through the same protocol as the four-month study. Once again, these were patients who had already been treated for invasive prostate cancer by either radical prostatectomy or radiation therapy, yet still had rising PSA levels, suggesting the treatment didn’t work and the cancer was on the move. “In those who have undergone a [cancer] recurrence, PSA typically tends to rise exponentially after prostatectomy or radiation therapy, reflecting the gradual, inexorable growth of the cancer in the body. After local treatment, the rate of PSA rise is the single best predictor of…development of overt metastatic disease, as well as of overall survival.” The next step would be hormonal therapy, which is chemical or surgical castration, but that has a list of side effects, including loss of libido, sexual function, strength, and vitality. “Therefore, many physicians employ a strategy of active surveillance” and try to hold off for as long as possible. If we’re just waiting, why not give diet a try?

Patients were “taught to increase intake of whole grains, vegetables, fruit, and legumes and to decrease meat, dairy, and refined carbohydrates.” Of all possible lifestyle interventions, why a whole food plant-based diet? If you look around the world, there are huge differences in prostate cancer rates, as you can see at 1:42 in my video, and our We’re #1! USA! USA! rates are up to a hundred times higher than some places in Asia, for example—and it’s not just genetic. Within one generation of migrating to the United States, cancer rates shoot up, and the grandkids of the immigrants end up with the same top-of-the-pile “approximate US rates.” A whole range of lifestyle factors have been looked at, but diet appears to have the greatest influence.

Specifically, “consumption of meat and dairy appears to increase risk, and consumption of plant-based foods appears to decrease risk.” Hence, the plant-based diet. A possible mechanism found in both meat and dairy products is arachidonic acid, an inflammatory compound that we make from omega-6-rich oils, like corn, sunflower, safflower, and cottonseed oils. It also comes “preformed” in animal-based foods and, in the American diet, is found particularly in chicken and eggs. In a petri dish, arachidonic acid appears to stimulate prostate cancer cell growth as much 200 percent, as you can see at 2:43 in my video.

So what happened when those researchers at University of California, San Diego asked men to remove processed and animal foods from their diet for six months? At 2:57 in my video, you can see a graph showing how fast the cancer patients’ PSA levels had been rising before starting the study. “In the absence of treatment, absolute levels of PSA tend to increase exponentially,” but upon eating more healthfully, nine of the ten study subjects showed an apparent slowing of cancer growth and four of the nine showed an apparent reversal in cancer growth. The average doubling time, an estimate of how long it would take for their cancer to double in size, slowed from doubling every year to closer to every ten years.

Other studies have used various diets and nutritional interventions, like vitamin supplements, but none has worked as well as this one—and the subjects’ compliance wasn’t even all that great. As you can see at 3:41 in my video, they did well in boosting their whole grain consumption in the first three months, but then backslid a bit, and they ate more vegetables, including a serving of greens, and an extra serving of fruit, at least early on. And, in the beginning, they at least ate one whole serving of legumes a day. So the researchers “did observe some [dietary] recidivism by 6 months,” with subjects sliding back into old habits. Given that, they checked to see if the study participants were better able to beat off the disease during that earlier period. And, indeed, at the end of the first three months, on average, there was PSA reversal. “Changes in the rate of rise in PSA, an indicator of disease progression, were in the opposite direction as changes in the intake of plant-based food groups, raising the provocative possibility that PSA may have inversely tracked intake of these foods and suggesting that adoption of a plant-based diet may have therapeutic potential in the management of this condition.”

Their findings suggest that, without further surgery, radiation, or chemotherapy, disease progression can be slowed or even reversed, despite “the prevailing scientific consensus…that cancer progression is largely irreversible.” The researchers state their “findings do not refute the benefits of standard therapies or guarantee that a plant-based diet and stress reduction will always induce remission,” but their results “do contribute to a growing [medical] literature that suggests that in at least some circumstances, cancer may be partly reversible and that modification of dietary and lifestyle factors may be able to help prevent disease spread”—all without getting their testicles cut off.

Hold on. We can make men’s bloodstreams nearly eight times better at suppressing cancer cell growth? See How Not to Die from Cancer.

It’s not all or nothing, though. Any movement we make towards healthy eating may help. See Prostate Cancer Survival: The A/V Ratio .


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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 About Coconuts, Coconut Milk, and Coconut Oil MCTs?

Do the medium-chain triglycerides in coconut oil and the fiber in flaked coconut counteract the negative effects on cholesterol and artery function?

Studies of populations who eat a lot of coconuts are “frequently cited” by those who sell coconut oil “as evidence that coconut oil does not have negative effects on cardiovascular health.” For example, there was an apparent absence of stroke and heart disease on the island of Kativa in Papua New Guinea. What were they eating? Their diets centered around tubers, like sweet potatoes, with fruits, greens, nuts, corn, and beans. Although they ate fish a few times a week, they were eating a largely whole food plant-based diet. It’s no wonder they may have had such low rates of artery disease. And, one of the whole foods they were eating was coconut, not coconut oil.

Now, if you go to Pukapuka, even more coconuts are eaten. In fact, as you can see at 0:51 in my video What About Coconuts, Coconut Milk, and Coconut Oil MCTs?, there’s even an island where coconuts make up most of what people eat—and they do get high cholesterol. How can a population eating 87 percent plant-based, with no dairy and only rare consumption of red meat, chicken, and eggs, have cholesterol levels over 200? Well, they’re eating all those coconuts every day. What are their disease rates like? We don’t know. There are no clinical surveys, no epidemiological death data, and no autopsies. Some EKGs were taken, which can sometimes pick up evidence of past heart attacks, but they found few abnormalities. The sample was too small to be a definitive study, though. And, even if they did have low disease rates, they weren’t eating coconut oil—they were eating coconut in its whole form.

Coconut oil proponents pointing to these studies is like the high fructose corn syrup lobby pointing to studies of healthy populations who eat corn on the cob or the sugar industry pointing to studies on fruit consumption and saying you can eat all the refined sugar you want. But fruit has fiber and so do coconuts. Just as adding psyllium fiber (Metamucil) to coconut oil can help blunt the adverse effects on cholesterol, fiber derived from defatted coconut itself can reduce cholesterol levels as much as oat bran. What’s more, the plant protein in coconuts, which is also missing from the oil, may help explain why whole coconuts may not have the same effects on cholesterol. Although coconut fat in the form of powdered coconut milk may not have the same effects on cholesterol as coconut oil, frequent consumption, defined as three or more times a week, has been associated with increased risk of vascular disease, stroke, and heart disease. And, no wonder, as coconut milk may acutely impair artery function as badly as a sausage and egg McMuffin.

Researchers tested three different meals including a Western high-fat meal that “consisted of an Egg McMuffin®, Sausage McMuffin®, 2 hash brown patties and a non-caffeinated beverage (McDonald’s Corporation)” a local high-fat meal, and an “isocaloric low-fat meal.” The study was conducted in Singapore, so the more traditional local high-fat meal was rice cooked in coconut milk and served with anchovies and an egg. These two different high-fat meals were put up against the same amount of calories in an unhealthy low-fat meal of Frosted Flakes, skim milk, and juice. At 3:21 in my video, you can see the artery function—that is, its ability to relax normally—before and after eating each of the three meals. Researchers found that artery function is significantly crippled within hours of consuming the McMuffins and also the local high-fat meal with coconut milk. So, whether the fat is mostly from meat and oil or from coconut milk, the arteries clamped down similarly, whereas that horrible sugary breakfast had no bad effect on artery function. Why? Because as terrible as the Frosted Flakes meal was, it had no saturated fat at all. (It also didn’t have contain any eggs, so that might have helped, too.)

Coconut oil proponents also try to argue that coconut oil has MCTs, medium-chain triglycerides, which are shorter-chain saturated fats that aren’t as bad as the longer-chain saturated fats in meat and dairy. You can’t apply the MCT research to coconut oil, though. Why not? Well, MCT oil is composed of MCTs—about 50 percent of the medium-chain fat caprylic acid and the other 50 percent of the MCT capric acid—whereas those MCTs make up only about 10 percent of coconut oil. Most of coconut oil is the cholesterol-raising, longer-chain saturated fats, lauric and myristic. “It is therefore inaccurate to consider coconut oil to contain either predominantly medium-chain fatty acids or predominantly medium-chain triglycerides. Thus, the evidence on medium-chain triglycerides cannot be extrapolated to coconut oil.”

It’s actually quite “a common misconception” that the saturated fat in coconut oil is comprised of mainly MCTs. Actually, as we discussed, coconut oil is mainly lauric and myristic, both of which have potent bad LDL cholesterol-raising effects. “Coconut oil should therefore not be advised for people who should or want to reduce their risk of CHD,” coronary heart disease, which is the number-one killer of U.S. men and women. The beef industry, for example, loves to argue that beef fat contains stearic acid, a type of saturated fat that doesn’t raise cholesterol. Yes, but it also has palmitic and myristic acids that, like lauric acid, do raise cholesterol, as you can see at 5:12 in my video.

If you compare the effects of different saturated fats, as you can see at 5:29 in my video, stearic acid does have a neutral effect on LDL, but palmitic, myristic, and lauric acids shoot it up—and, frankly, so may MCT oil itself, as it bumps up LDL 15 percent compared to control. Bottom line? “Popular belief”—spread by the coconut oil industry—“holds that coconut oil is healthy, a notion not supported by scientific data.” The science just doesn’t support it.

So, basically, “coconut oil should be viewed no differently” from animal sources of dietary saturated fat. A recent review published in the Journal of the American College of Cardiology put it even more simply in its recommendations for patients. When it comes to coconut oil, “avoid.”

Okay, but doesn’t saturated fat boost HDL, the so-called good cholesterol? Check out Coconut Oil and the Boost in HDL “Good” Cholesterol.


Isn’t coconut oil supposed to be good for Alzheimer’s, though? See my video Does Coconut Oil Cure Alzheimer’s?

If you want to learn more about the original McMuffin artery studies, see The Leaky Gut Theory of Why Animal Products Cause Inflammation.

You may also be interested in Flashback Friday: Coconut Oil and Abdominal Fat.

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: