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:

What About the Trans Fat in Animal Fat?

The years of healthy life lost due to our consumption of trans fats are comparable to the impact of conditions like meningitis, cervical cancer, and multiple sclerosis. But, if “food zealots” get their wish in banning added trans fats, what’s next? I explore this in my video Banning Trans Fat in Processed Foods but Not Animal Fat.

Vested corporate interests rally around these kinds of slippery slope arguments to distract from the fact that people are dying. New York Mayor Bloomberg was decried as a “meddling nanny” for his trans fat ban and attempt to cap soft drink sizes. How dare he try to manipulate consumer choice! But isn’t that what the food industry has done? “Soft drink portion sizes have grown dramatically, along with Americans’ waistlines.” In 1950, a 12-ounce soda was the king-sized option. Now, it’s the kiddie size. Similarly, with trans fats, it was the industry that limited our choice by putting trans fats into everything without even telling us. Who’s the nanny now?

New York City finally won its trans fat fight, preserving its status as a public health leader. “For example, it took decades to achieve a national prohibition of lead paint, despite unequivocal evidence of harm,” but New York City’s Board of Health led the way, banning it “18 years before federal action.”

There’s irony in the slippery slope argument: First, they’ll come for your fries; next, they’ll come for your burger. After the trans fat oil ban, one of the only remaining sources of trans fat is in the meat itself. “Trans fats naturally exist in small amounts in the fat in meat and milk,” as I’ve discussed before in my video Trans Fat in Meat and Dairy. Before the trans fat ban, animal products only provided about one fifth of America’s trans fat intake, but since the U.S. trans fat ban exempts animal products, they will soon take over as the leading source. As you can see at 2:09 in Banning Trans Fat in Processed Foods but Not Animal Fat, now that added trans fats are banned in Denmark, for example, the only real trans fat exposure left is from animal products found in the U.S. dairy, beef, chicken fat, turkey meat, lunch meat, and hot dogs, with trace amounts in vegetable oils due to the refining process.

The question is: Are animal trans fats as bad as processed food trans fats? As you can see at 2:38 in my video, a compilation of randomized interventional trials found that they both make bad cholesterol go up and they both make good cholesterol go down. So, both animal trans fats and processed food trans fats make the ratio of bad to good cholesterol go up—which is bad. Therefore, all trans fats cause negative effects “irrespective of their origin.” The researchers suspect that also removing natural trans fats from the diet could prevent tens of thousands of heart attacks, but unlike processed foods, you can’t remove trans fats from milk and meat because trans fats are there naturally.

The livestock industry suggests that a little bit of their trans fats might not be too bad, but you saw the same everything-in-moderation argument coming from the Institute of Shortening and Edible Oils after industrial trans fats were first exposed as a threat. The bottom line is “that intake of all sources of trans fat should be minimized.” The trans fat in processed foods can be banned, and just adhering to the current dietary guidelines to restrict saturated fat intake, which is primarily found in meat and dairy, would automatically cut trans fat intake from animal fats.

The reason no progress may have been made on animal trans fat reduction in Denmark is because The Danish Nutrition Council that pushed for the trans fat ban was a joint initiative of The Danish Medical Association and The Danish Dairy Board. They recognized that “the economic support from The Danish Dairy Council could be perceived as problematic” from a scientific integrity point of view, but, not to worry—“The Danish Medical Association expanded the Executive Board and the funding members to also include the Danish pork industry, the Danish meat industry, The Poultry and Egg Council and The Danish Margarine Industry Association.”

If people want to eat trans fat, isn’t that their right? Yes, but only if they’re informed about the risks—yet The Food Industry Wants the Public Confused About Nutrition.

For more on the industry pushback, see my video Controversy Over the Trans Fat Ban.

There does not appear to be a safe level of exposure to trans fat—or to saturated fat or dietary cholesterol, for that matter. See Trans Fat, Saturated Fat, and Cholesterol: Tolerable Upper Intake of Zero.


If you find these videos about industry influence on public policy compelling, check out my many others, including:

Note that the concept of raising or lowering HDL (the so-called good cholesterol) playing a causal role in heart disease has come into question. See Coconut Oil and the Boost in HDL “Good” Cholesterol.

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:

Decreasing Inflammation and Oxidation After Meals

Within hours of eating an unhealthy meal, we can get a spike in inflammation, crippling our artery function, thickening our blood, and causing a fight-or-flight nerve response. Thankfully, there are foods we can eat at every meal to counter this reaction.

Standard American meals rich in processed junk and meat and dairy lead to exaggerated spikes in sugar and fat in the blood, as you can see at 0:13 in my video How to Prevent Blood Sugar and Triglyceride Spikes after Meals. This generates free radicals, and the oxidative stress triggers a biochemical cascade throughout our circulation, damaging proteins in our body, inducing inflammation, crippling our artery function, thickening our blood, and causing a fight-or-flight nerve response. This all happens within just one to four hours after eating a meal. Worried about inflammation within your body? One lousy breakfast could double your C-reactive protein levels before it’s even lunchtime.

Repeat that three times a day, and you can set yourself up for heart disease. You may not even be aware of how bad off you are because your doctor is measuring your blood sugar and fat levels while you’re in a fasting state, typically drawing your blood before you’ve eaten. What happens after a meal may be a stronger predictor of heart attacks and strokes, which makes sense, since this is where most of us live our lives—that is, in a fed state. And it’s not just in diabetics. As you can see at 1:30 in my video, if you follow non diabetic women with heart disease but normal fasting blood sugar, how high their blood sugar spikes after chugging some sugar water appears to determine how fast their arteries continue to clog up, perhaps because the higher the blood sugars spike, the more free radicals are produced.

So, what are some dietary strategies to improve the situation? Thankfully, “improvements in diet exert profound and immediate favorable changes…,” but what kind of improvements? “Specifically, a diet high in minimally processed, high-fiber, plant-based foods such as vegetables and fruits, whole grains, legumes, and nuts,”—antioxidant, anti-inflammatory whole plant foods—“will markedly blunt the post-meal increase” in sugar, fat, and inflammation.

But what if you really wanted to eat some Wonder Bread? As you can see at 2:23 in my video, you’d get a big spike in blood sugar less than an hour after eating it. Would it make a difference if you spread the bread with almond butter? Adding about a third of a cup of almonds to the same amount of Wonder Bread significantly blunts the blood sugar spike.

In that case, would any low-carb food help? Why add almond butter when you can make a bologna sandwich? Well, first of all, plant-based foods have the antioxidants to wipe out any excess free radicals. So, nuts can not only blunt blood sugar spikes, but oxidative damage as well. What’s more, they can even blunt insulin spikes. Indeed, adding nuts to a meal calms both blood sugar levels and insulin levels, as you can see at 3:02 in my video. Now, you’re probably thinking, Well, duh, less sugar means less insulin, but that’s not what happens with low-carb animal foods.

As you can see at 3:23 in my video, if you add steamed skinless chicken breast to your white rice, you get a greater insulin spike than if you had just eaten the white rice alone. So, adding the low-carb plant food made things better, but adding the low-carb animal food made things worse. It’s the same with adding chicken breast to mashed potatoes—a higher insulin spike with the added animal protein. It is also the same with animal fat: Add some butter to a meal, and get a dramatically higher insulin spike from some sugar, as you can see at 3:45 in my video.

If you add butter and cheese to white bread, white potatoes, white spaghetti, or white rice, you can sometimes even double the insulin reaction. If you add half an avocado to a meal, however, instead of worsening, the insulin response improves, as it does with the main whole plant food source of fat: nuts.


I’ve covered the effect adding berries to a meal has on blood sugar responses in If Fructose Is Bad, What About Fruit?, and that raises the question: How Much Fruit Is Too Much?

In addition to the all-fruit jam question, I cover The Effects of Avocados and Red Wine on Postprandial Inflammation.

Vinegar may also help. See Can Vinegar Help with Blood Sugar Control?.

Perhaps this explains part of the longevity benefit to nut consumption, which I discuss in Nuts May Help Prevent Death.

I also talk about that immediate inflammatory reaction to unhealthy food choices in Best Foods to Improve Sexual Function.

Surprised by the chicken and butter reaction? The same thing happens with tuna fish and other meat, as I cover in my video Paleo Diets May Negate Benefits of Exercise.

Also check:

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: