Does Nutritional Yeast Trigger Crohn’s Disease?

Is the exaggerated reaction of many Crohn’s disease patients to baker’s, brewer’s, and nutritional yeast just a consequence of their inflamed leaky gut, or might the yeast be a contributing cause?

“Baker’s Yeast in Crohn’s Disease—Can It Kill You?” is the inflammatory title (no pun intended) of a 1999 journal article. Crohn’s disease is an inflammatory bowel disease. Might baker’s yeast, which is the same yeast as brewer’s yeast, which is the same yeast as nutritional yeast, play a role in Crohn’s disease? I explore this in my video Does Nutritional Yeast Trigger Crohn’s Disease?

It all started with a study published in 1988 that showed that people with Crohn’s disease tend to have more antibodies to yeast than people without Crohn’s, as you can see at 0:32 in my video. Antibodies are like homing devices our immune system makes to attack foreign invaders, and cell-mediated immunity, where our white blood cells attack invaders directly, is another part of our immune system. The same hypersensitive reaction to yeast was found in the white blood cells of Crohn’s disease patients, as well.

If you draw blood from healthy people—even bakers who are around yeast all the time—and then you expose their immune system’s white blood cells to yeast, nothing happens. The white blood cells just ignore the yeast because it’s typically harmless. But, “[i]n striking contrast with healthy controls,” if you do the same with Crohn’s disease patients, they show “a marked increase in their lymphocyte proliferation when exposed to yeast” as their white blood cells go crazy.

Now, when I say yeast is “typically harmless,” if you have cancer or AIDS or are immunocompromised, you could potentially get infected from home-brewed beer or probiotic yeast supplements, but researchers don’t think the yeast is actually infecting Crohn’s patients. People with Crohn’s may just be hypersensitive to exposure to the inactive, dead yeast in typical food products, which may help explain why they get better when they rest their bowels by fasting.

In fact, that’s why we add yeast extracts and proteins to vaccines as an adjuvant, an irritant like aluminum, to make the vaccines work better by heightening the immune response. But might that be raising the risk of autoimmune disease, boosting our immune response a little too much, especially in people who may be genetically susceptible, like those with Crohn’s?

The greater the anti-yeast response, the more severe the disease. This was seen in children and may also be the case for adults, too. Should we try a yeast-free diet for Crohn’s patients to see whether they get better? Hold on. Just because anti-yeast antibodies are associated with Crohn’s disease doesn’t mean the reaction to yeast is causing the Crohn’s disease. Maybe the Crohn’s disease is causing the reaction to yeast.

Think about it: Crohn’s causes an inflamed, leaky gut, so maybe the Crohn’s came first and allowed yeast particles to leak into the bloodstream, which resulted in the anti-yeast reaction. Instead of the yeast reaction triggering the Crohn’s, maybe the Crohn’s triggered the yeast reaction. “Whether these antibodies are triggering IBD [inflammatory bowel disease] or are only a consequence of gut inflammation without a disease-aggravating role remained elusive.” How could we test it? If anti-yeast antibodies are just a consequence of food particles leaking through the gut, Crohn’s patients should have antibodies to all sorts of common foods, but they don’t. As you can see at 3:18 in my video, there were higher anti-yeast antibodies in Crohn’s disease patients compared with controls, but there was no greater reaction in Crohn’s patients to milk, wheat, or egg proteins, all of which would presumably leak through, too.

We can also look at it the other way. Instead of other foods, what about other inflammatory bowel disorders? Ulcerative colitis and acute gastroenteritis could cause guts to get inflamed and leaky, too, yet there is no increased yeast reaction. There does appear to be something unique about the relationship between yeast and Crohn’s, but might inflamed Crohn’s intestines just uniquely and selectively allow yeast through? If you cut out the Crohn’s, can you stop the yeast reaction? Crohn’s gets so bad that most patients have to go under the knife and get sections of their intestines removed. So, when the inflamed segments are removed, does the yeast reaction go away? No, as you can see at 4:18 in my video, there is no post-operative change. So, a change in Crohn’s activity doesn’t lead to a change in the yeast reaction, but we still have to prove that the yeast reaction comes first.

Thankfully, the Israeli military systematically draws blood from its recruits and follows their health for years, so we can go back and check the blood of newly diagnosed Crohn’s victims. And, indeed, those who went on to have Crohn’s were disproportionately reacting to yeast years earlier. So, it’s not as though yeast reactions were low until Crohn’s hit and then shot up. As you can see at 4:54 in my video, yeast reactivity crept up year after year before the diagnosis. It is possible there was some subclinical gut leakiness in the years preceding diagnosis that led to the yeast reaction, but there doesn’t appear to be any association between yeast reactivity and gut leakiness. Given that, do high blood levels of anti-yeast antibodies result from leakiness of the gut barrier in Crohn’s disease? No, that does not appear to be the case. So, if Crohn’s isn’t leading to the yeast reaction, does that mean the yeast reaction is leading to the Crohn’s?

Any time two things appear to be associated—in this case, reacting to yeast (X) and Crohn’s disease (Y)—they can appear tied together because X causes Y or Y causes X. Well, as we’ve discussed, it appears that Y, Crohn’s disease, does not cause X, a yeast reaction, but does that mean that X causes Y? There’s another option. There may be a third factor, Z, that causes both X and Y independently. Maybe the only reason yeast reactivity and Crohn’s disease appear to go together is that there’s a third factor causing them both—for instance, Candida, which I cover in my video Is Candida Syndrome Real?.

This is something I warned people about long ago on social media. It takes some time from when I first research a topic until the video is produced and uploaded to the site, so for breaking or important news, I rely on our Facebook, Twitter, Instagram, and YouTube channels to let everyone know as quickly as I can. Please consider following along and joining in on the conversation.


Warned about? So is yeast really a potential problem? Yes, and not just for Crohn’s. This is the first of a four-part video series. See also:

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:

Arsenic in Rice Milk, Rice Krispies, and Brown Rice Syrup

I recommend people switch away from using rice milk

For kids and teens, the amount of arsenic flowing through their bodies was found to be about 15 percent higher for each quarter cup of rice consumed per day, and a similar link was found in adults. A study of pregnant women found that consuming about a half cup of cooked rice per day could raise urine arsenic levels as much as drinking a liter of arsenic-contaminated water at the current upper federal safety limit. These findings “suggest that many people in the United States may be exposed to potentially harmful levels of arsenic through rice consumption.” which I explore in my video Arsenic in Rice Milk, Rice Krispies, and Brown Rice Syrup.

Do you know where Americans get most of their rice arsenic? From Rice Krispies, though brown rice crisps cereal may have twice as much, as I discuss in my video Arsenic in Rice Milk, Rice Krispies, and Brown Rice Syrup.

“Organic brown rice syrup (OBRS) is used as a sweetener in organic food products as an alternative to high-fructose corn syrup.” Big mistake, as organic brown rice syrup products “may introduce significant concentrations” of toxic arsenic into people’s diets. For example, two energy chews sweetened with brown rice syrup might hit the provisional upper daily arsenic intake based on the water standards.

“Toddler formulas with added organic brown rice syrup have 20 times higher levels of inorganic [toxic] arsenic than regular formulas,” and in older children, thanks to brown rice syrup, a few cereal bars a day “could pose a very high cancer risk.”

What about rice milk? A consensus statement of both the European and North American societies for pediatric nutrition recommends the “avoidance of rice drinks for infants and young children,” and, generally, toxic “inorganic arsenic intake in infancy and childhood should be as low as possible.”

To this end, the United Kingdom has banned the consumption of rice milk for young children, a notion with which Consumer Reports concurred, recommending no servings a week of rice milk for children and no more than half a cup a day for adults, as you can see at 1:56 in my video.

The arsenic in various brands of rice milk ranges wildly—in fact, there’s a 15-fold difference between the highest and lowest contamination, suggesting manufacturers could make low arsenic rice milk if they wanted. As you can see at 2:16 in my video, Consumer Reports found rice drinks from Pacific and Rice Dream brands were right about average, though, for Rice Dream, it appears the vanilla or chocolate flavors may be lower. It doesn’t seem we have anything to worry about with rice vinegar, but rice pasta and rice cakes end up similar to pure rice in terms of arsenic levels, which makes sense because that’s pretty much what they are—pure rice. However, pasta is boiled, so we’d expect the levels to be cut 40 to 60 percent, like when you boil and drain rice.

If you just couldn’t live without rice milk for some reason, you could make your own using lower arsenic rice, like brown basmati from India, Pakistan, or California, but then your homemade rice milk might have even less nutrition, as most of the commercial brands are at least fortified. Better options might be soy, oat, hemp, or almond milk, though you don’t want kids to be drinking too much almond milk. There have been a few case reports of little kids drinking four cups a day and running into kidney stone problems due to its relatively high oxalate content, which averages about five times more than soy milk. More on oxalates in my video series starting with Oxalates in Spinach and Kidney Stones: Should We Be Concerned?

I have about 40 videos that touch on soy milk, discussing such topics as how it may normalize development in girls and reduce breast cancer risk, as well reduce prostate cancer risk in men. Some of the latest science on soy milk includes an association with better knee x-rays, suggesting protection from osteoarthritis, and an interventional study suggesting improved gut health by boosting the growth of good bacteria. However, drinking 3 quarts a day, which is 10 to 12 daily cups, for a year may inflame your liver, but two cups a day can have an extraordinary effect on your cholesterol, causing a whopping 25 percent drop in bad cholesterol after just 21 days.

An ounce and a half of almonds, about a handful, each day, can drop LDL cholesterol 13 percent in six weeks and reduce abdominal fat, though a cup of almond milk only contains about ten almonds, which is less than a third of what was used in the study. So, it’s not clear if almond milk helps much, but there was a study on oat milk compared to rice milk. As you can see at 4:37 in my video, five weeks of oat milk lowered bad cholesterol, whereas rice milk didn’t, and even increased triglycerides and may bump blood pressure a bit. However, the oat milk only dropped LDL about 5 percent and that was with three cups a day. As plant-based alternatives go, it appears soy milk wins the day.

So, why drink rice milk at all when there are such better options? There really isn’t much nutrition in rice milk. In fact, there are case reports of severe malnutrition in toddlers whose diets were centered around rice milk due to multiple food allergies. Infants and toddlers have increased protein requirements compared to adults, so if the bulk of a child’s diet is rice milk, coconut milk, potato milk, or almond milk, they may not get enough, as you can see at 5:23 in my video. In fact, cases of kwashiorkor—that bloated-belly protein- and calorie-deficient state of malnutrition—due to rice milk have been reported in Ethiopia…and Atlanta, Georgia, because literally 99 percent of the child’s diet was rice milk. So, these malnutrition cases were not because they drank rice milk, but rather because they drank rice milk nearly exclusively. I just use these examples to illustrate the relative lack of nutrition in rice milk. If you’re going to choose a milk alternative, you might as well go for one that has less arsenic—and more nutrition.

I have released several videos on soy milk, but only one on almond milk video so far: Prostate Cancer and Organic Milk vs. Almond Milk. I plan on producing many more on choosing between various milk options, so stay tuned.


If you’ve missed any of the useful material on dietary arsenic I’ve also shared, please see:

The final four videos in this series take all of this information and try to distill it into practical recommendations:

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: