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:

Is Candida Syndrome Real?

Does the presence of Candida in stool correlate with “Candida-hypersensitivity” symptoms, such as headaches and tiredness? And what happens when people are placed on a high-sugar diet?

Despite its extensive use in the brewing and baking industries, only about 5 percent of healthy people—1 in 20—have anti-yeast antibodies in their bloodstream, whereas that percentage is more like 60 or 70 percent in people with Crohn’s disease. Most people with Crohn’s have antibodies that react to regular baker’s, brewer’s, or nutritional yeast, which are all just different forms of a yeast known as Saccharomyces cerevisiae.

But baker’s/brewer’s/nutritional yeast has never been directly implicated in Crohn’s. Maybe the antibodies are a direct reaction to it, or maybe they are a reaction to another yeast altogether and just mistakenly cross-react with regular yeast. Indeed, it was discovered that antibodies against Candida, a totally different kind of yeast (the yeast that causes thrush and vaginal yeast infections), can cross-react with Saccharomyces. Is it possible that baker’s/brewer’s/nutritional yeast was just an innocent bystander all along? I investigate this in my video Is Candida Syndrome Real?.

For nearly 30 years, we’ve known that antibodies to Saccharomyces are linked to Crohn’s disease, but instead of bread, beer, and nutritional yeast leading to Crohn’s disease, perhaps Candida is causing the Crohn’s disease and the antibodies. Or maybe Candida is the innocent bystander, and exposure to food and beverage yeast is the real culprit. You don’t know until you put it to the test: Remove yeast from the diet of Crohn’s patients, and see if they get better. If they do, then yeast was indeed the culprit. If they don’t? Then maybe Candida is the real cause.

Before I get to the study, let me first bust some Candida myths. Candida is a normal constituent of our gut flora. Get some Candida in your bloodstream, though, and it can cause a life-threatening infection. But it is normal to have some Candida in your mouth or colon—what’s important is location! location! location! It’s similar to how having stool bacteria in our colon is normal, but stool bacteria in our blood or a wound would be bad. Because of the ability of Candida to cause problems in the wrong location or in people who are immunocompromised, a Candida-syndrome theory arose, linking the presence of Candida to all sorts of health problems. This led to “mycophobia”—or fungalphobia—“spreading due to the false interpretation” that the finding of Candida in your mouth or stool is evidence of some kind of infection, rather than just being totally normal. (If you think the authors of that paper were being a little overdramatic with their phobia talk, just google “Candida” and you’ll see.)

Not only is it normal to have Candida in your gut, you apparently can’t get rid of it even if you wanted to. Give people powerful antifungal drugs, and you can drop levels down, but they pop right back up again as soon as you stop the antifungals. What about the concept that sugar feeds yeast, so you should go on a low sugar diet? It doesn’t make much sense because sugars should get absorbed high up in the small intestine and never even make it down into the colon unless you’re lactose intolerant. Indeed, there appears to be no correlation between Candida counts and sugar consumption. You can put people on a high-sugar diet by adding an additional 14 spoonfuls of sugar to their diets and still not see an effect. Of course, there are lots of science-based reasons to cut sugar from your diet, but Candida does not appear to be one of them.

There does not appear to be good “evidence for the existence of the so-called “Candida-syndrome” at all. But those are fighting words! “Few illnesses have sparked as much hostility between the medical community and a segment of the lay public as the chronic candidiasis syndrome.” The medical community has dismissed purported sufferers as emotionally disturbed and they’ve also been dubbed just plain crazy. Of course, you can’t just come out and call people crazy. “Psychiatric diagnoses need to be presented gently…” Some patients, for example, prefer to believe their mental illness is caused by the Candida, in which case doctors may just pat them on the head so they’ll take their pills. “However, patients self-diagnosed as having the yeast connection will only infrequently relinquish their illness”—some even to the extent they attempt to use their yeast as a drunk driving defense: I wasn’t drinking, your Honor. My yeast was just self-brewing beer in my gut!

The whole concept of Candida syndrome is officially derided by the American Academy of Allergy and Immunology as “speculative and unproven,” without any proof that it exists. The presumption that “the ubiquitous C. albicans [Candida] has some toxic effect on the human immune system…[is] without a trace of clinical evidence or scientific proof.” If you want proof, argued a response to the study, what about the millions of unnecessary tonsillectomy surgeries and all the radical mastectomies? At least putting people on low-sugar diets doesn’t disfigure them. Though some anti-Candida therapies can be “potentially dangerous,” antifungal drugs might breed resistance and can have side effects. Nystatin isn’t so bad, but ketoconazole can damage your liver. And, indeed, there are reports of people being treated for what may be a fake diagnosis and ending up in quite dire straits because of it. So, it’s important to know if the syndrome actually exists. Researchers decided to put it to the test in a super simple study: Give subjects stool-tubes to take samples, and ask them questions about their symptoms—headaches, stomachaches, tiredness, and all the other typical Candida syndrome symptoms. The result? The researchers found no relationship to whether or not the subjects had Candida growing in their guts. No hints of Candida syndrome could be found.


This was a bit of a tangent from the topic of my video Does Nutritional Yeast Trigger Crohn’s Disease?. I return to that topic in my video Is Nutritional Yeast Healthy for Everyone? and then offer hope for sufferers of another inflammatory condition in Dietary Cure for Hidradenitis Suppurativa.

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 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: