Benefits of Nutritional Yeast to Prevent the Common Cold

Image Credit: Sally Plank

Benefits of Nutritional Yeast to Prevent the Common Cold

Natural immunomodulators that can help regulate our immune system without side-effects have been sought for centuries, and all the while they’ve been sitting in the produce aisle. Plants produce thousand of active compounds, many of which modulate our immune system, but we can’t forget the fungi (see Boosting Immunity While Reducing Inflammation).

Mushrooms have been used for centuries as folk remedies, and for good reason. Some have been shown to boost immune function, so much so that a type of fiber found in shiitake mushrooms is approved for use as adjunct chemotherapy, injected intravenously to help treat a variety of cancers by rallying our immune defenses.

More than 6,000 papers have been published on these so-called beta glucans, but almost all of the data about preventing infections had come from petri dish or lab animal studies, until a few years ago when a series of experiments on athletes showed beneficial effects in marathon runners (see Preserving Immune Function in Athletes With Nutritional Yeast). What about the rest of us? We didn’t know… until now.

As I explore in my video, Nutritional Yeast to Prevent the Common Cold, beta glucan fiber found in baker’s, brewer’s, and nutritional yeast helps to maintain our body’s defense against pathogens even in nonathletes, according to a double-blind, randomized, placebo-controlled trial. The recurrence of infections with the common cold was reduced by 25% in those that ate the equivalent of about a spoonful of nutritional yeast a day, and they had fewer cold-related sleeping difficulties when they did get sick.

What about half a spoonful a day? Still worked! Subjects experienced a big drop in common cold incidence and a reduction in symptoms as well. Why is this? This study found that not only were upper respiratory infection symptoms diminished, but that mood states appeared to improve, for example, a significant boost in feelings of “vigor.” So, the researchers suggest that maybe the yeast fiber is able to counteract the negative effects of stress on the immune system.

In terms of side effects, two folks reported stomachaches, but they were both in the placebo group.

Unlike antibiotics and antivirals, which are designed to kill the pathogens directly, these yeast compounds instead appear to work by stimulating our immune defenses, and as such don’t share the same antibiotic side effects. They stimulate our immune defenses presumably because our body recognizes them as foreign. But if it’s treated like an invader, might it trigger an inflammatory response? Turns out these fiber compounds may actually have an anti-inflammatory effect, suggesting nutritional yeast may offer the best of both worlds, boosting the infection fighting side of the immune system while suppressing inflammatory components.

Yeast is high in purines; so, those with gout, uric acid kidney stones, and new organ transplant recipients may want to keep their intake to less than a teaspoon a day. But is there any downside for everyone else? In California, some packages of nutritional yeast are slapped with prop 65 warning stickers, suggesting there’s something in it exceeding cancer or birth defect safety limits. I called around to the companies, and it turns out the problem is lead.  California state law says a product cannot contain more than half of a microgram of lead per daily serving; so, I contacted the six brands I knew about and asked them how much lead was in their products.

KAL originally said “<5 ppm,” but when we called back they said “<3 ppm.” Even if it’s 3, that translates into less than 45 micrograms per serving, nearly a 100 times more than the California limit. But perhaps that’s better than Bob’s Red Mill or Frontier Coop, who evidently don’t test at all. But at least they got back to me. Redstar brand failed to respond to multiple attempts to contact them. Now Foods said they test for lead and claim that at least their recent batches meet the less than a half a microgram California standard. Unfortunately, despite repeated requests, they would not provide me with documentation to substantiate their numbers. My favorite response was from Bragg’s who sent me the analysis certificate from the lab showing less than 0.01 ppm, which means at most less than half the California standard, which I believe is the most stringent in the world. To put the numbers in context, in determining how much lead manufacturers can put into candy likely to be frequently consumed by small children, the Food and Drug Administration would allow about 2 micrograms a day in the form of lollipops, but as far as I’m concerned, the less lead the better.

I was so frustrated by the lack of transparency, I decided to test them for lead myself. hired an independent lab to conduct our own tests for lead and shipped out 8 samples of nutritional yeast in their original package. The lab used standard practices for lead testing known as Official Methods of Analysis set by AOAC International. Lab technicians determined the lead values based on California Prop 65 standards. Here are the results from the brands we tested:

Bob’s Red Mill  – Test report shows no detectable lead (<0.01 ppm).

Bragg – Test report shows no detectable lead (< 0.01 ppm).

Dr. Fuhrman –  Test report shows no detectable lead (< 0.01 ppm).

Frontier Coop – Test report shows lead levels at 0.021 ppm. It would take six tablespoons a day (based on the manufacture’s listed density) to exceed the California Office of Environmental Health Hazard Assessment Maximum Allowable Dose Level (MADL) for chemicals causing reproductive toxicity.*

KAL – Test report shows lead levels at 0.011 ppm. It would take seven tablespoons a day to exceed the MADL.*

NOW Foods – Test report shows no detectable lead (< 0.01 ppm).

Red Star – Test report shows no detectable lead (< 0.01 ppm).

Whole Foods – Test report shows lead levels at 0.012 ppm. It would take six tablespoons a day to exceed the MADL.*

So, what do all those numbers mean? None of the brands tested exceeded California prop 65 standards. No matter what brand, consuming a typical serving (2 tablespoons) per day is still well within safe limits.

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:

* The Maximum Allowable Dose Level for lead as a developmental toxin is 0.5 micrograms a day. How are MADL’s calculated? Basically scientists figure out what the “no observable effect level” is, the level at which no birth defects or reproductive toxicity can be found, and then introduce a 1000-fold safety buffer. So for example, let’s say there’s some chemical that causes birth defects if expectant moms are exposed to two drops of the chemical a day, but there’s no evidence that one drop a day is harmful. Do they set the Maximum Allowable Dose Level at one drop? No, they set it at 1/1000th of a drop to account for scientific uncertainty and to err on the side of caution. So by saying six tablespoons a day of nutritional yeast may exceed the MADL is in effect saying that the level of lead found in 6,000 tablespoons of nutritional yeast may cause birth defects. Like mercury, though, as far as I’m concerned the less lead exposure the better. I hope this will inspire companies to do further testing to see if the levels we found were just flukes.


Michael Greger M.D., FACLM

Michael Greger, M.D. FACLM, is a physician, New York Times bestselling author, and internationally recognized professional speaker on a number of important public health issues. Dr. Greger has lectured at the Conference on World Affairs, the National Institutes of Health, and the International Bird Flu Summit, testified before Congress, appeared on The Dr. Oz Show and The Colbert Report, and was invited as an expert witness in defense of Oprah Winfrey at the infamous "meat defamation" trial.

40 responses to “Benefits of Nutritional Yeast to Prevent the Common Cold

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  1. I have just become aware of the lead issue in supplements, particularly spices. Thank you for the testing on nutritional yeast.

    Frontier Coop spices have become a concern since there is no indication of country of origin. Specifically, I have just been researching their turmeric for information about lead to no avail. Discovering your testing results from their nutritional yeast product had me tossing the bottle of their turmeric and grinding the fresh local root from the farmers market into my smoothie.

  2. It’s hard to find a brand that is organic and does not have added folic acid, a synthetic form of folate which reports say has been linked to cancer and other health issues. I did find Sari brand on amazon that meets my criteria and I like it. Although I think nutritional yeast might cause me a skin reaction. I’m testing more. I’m not affiliate with Sari in any way.
    Mark G

  3. Dr. G, all of the nutritional yeast products you just mentioned are fortified with B6, B3, and other B vitamins. It’s the same thing as sticking a vitamin pill of chemical-based synthetic vitamins into nutritional yeast. I would be surprised to hear you are willing to even ingest nutritional yeast, based on this and on your, and a lot of other vegan doctors, advising that there is scientific evidence that synthetic B vitamins (other than B12) might not be a good idea. And these yeasts contain, uh, a whole lot. Could these studies today be tested out on both fortified and non-fortified to see where the yeast is helping from?
    Also, are there fruits and veggies that would be even better than using nutritional yeast, as far as the benefits you have highlighted in today’s post? Is it even necessary, maybe better to replace nutritional yeast with real food?

  4. Nutritional yeast inherently has B vitamins. If you look at the Nutrition Information panel of an unfortified brand (such as Sari Foods), you will see this.

    B12 is the obvious exception. You will only find that in fortified versions.

    1. yes, naturally high in b vitamins, but most nutritional yeast products on the store shelves are also fortified with synthetic vitamins. Especially the products Dr. Gregor has listed today. It is surprising to many in this vegan community that he has not addressed this synthetic vitamin concern, and whether or not he himself consumes synthetic vitamins via a fortified nutritional yeast.

      1. lindy: re: “he has not addressed … whether or not he himself consumes synthetic vitamins via a fortified nutritional yeast.” On page 375 of Dr. Greger’s book, How Not To Die, Dr. Greger shares that he enjoys putting chlorella and nutritional yeast on his popcorn.

  5. Hi,

    We noticed that the article did not mention that nutritional yeast can trigger migraines. Do you have any information on this phenomenon that could help someone to find a relatively “safe” level of nutritional yeast; e.g., one that provides health benefits without causing migraines or other problems that develop over time?


    1. Nutritional yeast CAN trigger migraines in SUSCEPTIBLE people. That is not everyone with migraine. Nutritional yeast is not my trigger. The same thing goes for bananas, chocolate, cheese, etc.

    2. Nutritional yeast CAN trigger migraines in SUSCEPTIBLE people. That is not everyone with migraine. Nutritional yeast is not my trigger. The same thing goes for bananas, chocolate, cheese, etc.

      Second try

  6. While I appreciate the effort of independently testing the different brands of nutritional yeast for lead content, please keep in mind:
    – this is only one data point of one sample of one production run
    – manufacturer quality processes are not necessarily standard
    – more meaningful results would be to test several bags within each production run and then repeat that on different production runs
    – the above is likely what the manufacturers actually do to arrive at their declared lead content values
    – if the manufacturers are willing share – would be nice to see the process they go through to declare their numbers and if they are subject to independent third-party audits

    Living in California, I see Prop 65 warnings everywhere. Most public buildings and stores have signs posted at the entrance (even the office where I work!). Most products I buy have a Prop 65 paper flyer inside. In the grand scheme of things, I fear the amount of lead I get from nutritional yeast is relatively just a drop in the ocean compared to what I am exposed to every day from apparently everything around me :( So I do understand we have to keep some things in perspective ;)

    I am not going to stop consuming nutritional yeast any time soon – and agree that theless lead is better.

  7. For those asking about the folic acid found in many nutritional yeast products: Word is that NutritionFacts will be doing some videos on folic acid. I’m not sure if/how that will change things. But maybe we will get some answers that help us decide whether or not to consume nutritional yeast.

    FYI: In the meantime, I have every intention of continuing to enjoy nutritional yeast in various sauces and on oatmeal/grains. Yummmm.

    1. Hi Dale, thanks for your question. I am one of the site moderators. Yeast is a living organism that requires a form of sugar for food and a slightly warm temperature to grow. This is why bakers “proof” their yeast to see if it is still active – alive and why they put bread in a warm place for several hours for the yeast to grow and release the gasses they make as part of their reproductive process. Baking or any high heat will kill them off so there will not be any active yeast in a finished product that has been exposed to high heat. This is why there are active cultures in yogurt and other fermented foods that have not been cooked or pasteurized as the higher heat would then render these organisms inactive. I hope this answers your question.

  8. I have been adding 1 TBS of Brewer’s Yeast to my morning shake for years. Brewer’s Yeast is not the same as Nutritional Yeast. I have been purchasing my brewer’s yeast from the Wellness Forum. According to Dr. Pam Popper, Wellness Forum Founder, brewer’s yeast and nutritional yeast are totally different. The Wellness Forum brewer’s yeast is not made from beer processing and has no additives, including vitamins.

  9. Nutritional yeast is from molasses.
    Most of the time fortified and brewed with synthetic ingredients.
    Brewers yeast is from beer. Has cromium. Much better. Many are not fortified.
    they also have proteins in amino acid structure. Use them as a source of nutrients and protein for weight lifting.

    1. You have problems possibly because some of yest weren’t dead actually, so they could reproduce themselves and provoke a disbyosis.
      Try to heat them for more than 60 degree or simply take pills from another manufacturer.

    2. I’ve tried it twice, dinner last night and again tonight, very! bad gas and bloating both times. Strangely doesn’t effect my partner (except for my ungodly wind) who has a multitude of intolerances. What gives?

  10. I have had very positive results from over 30 years of taking powdered brewers yeast, 2 tbsps per day, with some noticeable gaps in between but too much to go into online. Cure of dizziness, cure of palpitations etc.

  11. I use Dr. Fuhrman’s Nutritional Yeast because it is the only one I have found that contains no added folic acid. Folic acid has been linked to an increased risk of cancer so I am very careful as to which I use, and after doing my research Dr. Fuhrman’s is the only one I am sure of that does not have folic acid.

  12. I have enjoyed and appreciated reading about Nutritional Yeast and Folic Acid. I have been Vegan (plant based0 over 30 years. When I have tests done, my folic acid is ALWAYS higher than what is stipulated. I do not buy any vitamins, supplements, etc. with Folic Acid, sometimes hard to find.

    Any others on plant based diet found their folic acid, when tested, quite high?

  13. Thank you for doing the research on lead I appreciate it. I took nutritional brewers yeast from Lewis Labs for the high phosphorus content and it cured my sciatica. I am all for adding extra B vitamins to it because otherwise they are not balanced in the correct ratio for the body which can only use then in the right match to the lowest of them. So if you had 2 mg of B1 and 100 mg of B2 then the body would only use the 2 of B1 and 2 of B2. Most are not correctly balanced but some add extra to do so. I don’t know if I believe that folic acid is bad -my husband took it for gout for years 10 to 20 little 400 mcg tablets a day and also for preventing too much homocysteine and it helped both gout and heart trouble.

  14. Thank you for testing the batches of nutritional yeast. I learn so much from you and I share it with anyone who will listen. Onward to better health!

  15. Can beta glucan found in nutritional or brewer’s yeast be used by our bodies? Or is it true that our body cannot isolate the glucan out of yeast as said by Dr Vetvicka?

  16. Hi, Ana. Could you please share the source of this statement, so that we can evaluate it? I have seen nothing in the scientific literature to suggest that beta glucans from food cannot be used, but I would be interested in reviewing any additional information you may have. It is worth noting that Dr. Vetvicka is working on developing drugs and supplements. Why would anyone buy a drug or supplement, if the same benefits are available at reduced cost from food?

  17. How many grams are two tablespoons of nutritional yeast?
    How many grams is one cup of nutritional yeast?
    How many grams is one teaspoon of nutritional yeast?

    Thanks in advance!

  18. Hi Sandro, thanks for your question. On average, two tablespoons (about 30 ml) provides 60 calories with five grams of carbohydrates and four grams of fiber. A serving also provides 9 g of protein, which is complete protein, providing all nine amino acids the human body cannot produce. I cup is about 250 ml . 1 teaspoon is 5 g. I cup is about 6 oz.

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