Nutritional Yeast

Nutritional yeast is Saccharomyces cerevisiae — the same species as baker’s and brewer’s yeast — usually grown on molasses, then killed and dried into savoury, cheese-flavoured yellow flakes. Its best-supported benefit depends entirely on the label: fortified flakes are an easy, reliable source of vitamin B12 for vegans, while unfortified flakes contain essentially none. The popular claims that it “heals nerves” and “reduces anxiety” hold only where a B-vitamin deficiency is being corrected, and trials of purified yeast beta-glucan capsules show mixed effects on colds. Large helpings of fortified flakes can pass the upper limits for added niacin and folic acid, and dried yeast is among the most purine-dense foods measured — which matters if you have gout.

Table of Contents

  1. What It Is: Nutritional, Brewer’s and Baker’s Yeast
  2. Traditional and Historical Use
  3. What Is Actually in It: Fortified vs Unfortified
  4. Vitamin B12: The Real Benefit, Only When Fortified
  5. Protein and Amino Acids
  6. Beta-Glucans, Immunity and Colds
  7. Nerves and Anxiety: What B Vitamins Can and Cannot Do
  8. How to Use It
  9. Myths and Overclaims in the Popular Videos
  10. Safety, Interactions and Who Should Avoid It
  11. Key Research Papers
  12. Connections
  13. Featured Videos

What It Is: Nutritional, Brewer’s and Baker’s Yeast

Nutritional yeast is a single-celled fungus, Saccharomyces cerevisiae, sold as a food. Makers grow it the way baker’s yeast is grown commercially: in large, aerated tanks fed a sugary medium, usually cane or beet molasses — the dark syrup left behind when sugar is crystallised out of cane or beet juice (its grocery-shelf cousin is blackstrap molasses). When the batch is ready, the yeast is harvested, washed, inactivated with heat and dried into flakes or powder.

The word that matters is inactive. A 2022 review of yeast as a food describes commercial food yeast as “dead yeast cells with no leavening power” (Jach 2022), and many labels simply list the single ingredient as “inactive yeast” or “dried yeast.” Nutritional yeast cannot raise bread, ferment sugar or grow in your gut.

The same species turns up under several names, and they are not interchangeable:

Nutritional yeast is also not a probiotic. Probiotic yeast supplements contain living cells chosen to survive the gut; nutritional yeast contains none. See Probiotics for the live kind.

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Traditional and Historical Use

Yeast earned its reputation as a health food in the fight against pellagra, the niacin-deficiency disease of rough, reddened skin, diarrhoea and mental changes. In the first half of the twentieth century pellagra reached epidemic levels in the American South: at its peak, at least 250,000 cases and 7,000 deaths a year, for several decades, in 15 southern states (Bollet 1992). Investigators at the U.S. Public Health Service, led by Joseph Goldberger, found that yeast contained what they called the “pellagra-preventive factor” and that it was the most potent source of it they had — the factor was later identified as nicotinic acid, one form of niacin (vitamin B3). Doctors began treating pellagra with yeast, which was especially valuable for patients whose painful mouth sores kept them from swallowing ordinary food.

The most striking episode came in 1927. When the Mississippi River flooded, Goldberger arranged for the Red Cross to ship large quantities of yeast into the flood-stricken areas. The expected outbreak of pellagra did not happen — cases fell below their usual seasonal level — and after the emergency, when the yeast stopped, pellagra returned to its usual level (Bollet 1992). The disease itself is covered on our Pellagra page.

Two lessons from that history still apply. First, it is a story about correcting a deficiency: yeast worked because the people eating it were starved of niacin, not because it did anything special for people who were already well fed. Second, later efforts to turn fast-growing microbes, yeast among them, into a bulk protein food for a hungry world ran into a practical limit: their high nucleic-acid content, which the body breaks down to uric acid. Reviews of yeast protein note that microbial protein destined for food or feed should have its nucleic acids reduced to about 1%, because high intakes can cause gout and kidney stones in susceptible people (Jach 2022). That is one good reason to treat nutritional yeast as a seasoning rather than a staple.

Today nutritional yeast is best known as a seasoning in vegetarian and vegan kitchens, and the same 2022 review singles it out as a useful supplement food for vegan and vegetarian diets (Jach 2022).

Evidence tier: historical public-health experience with deficiency disease, later explained by the discovery of niacin.

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What Is Actually in It: Fortified vs Unfortified

“Nutritional yeast” is really two products sold under one name. Unfortified flakes contain only what the yeast cell itself made or took up while it grew. Fortified flakes have vitamins added — typically thiamine, riboflavin, niacin, vitamin B6, folic acid and vitamin B12, which is what the ingredient lists in USDA’s label database show. The two are very different.

What the yeast itself supplies (unfortified)

USDA’s FoodData Central has no generic record for nutritional yeast. Its closest is SR Legacy record FDC 175043, “Leavening agents, yeast, baker’s, active dry” — the same species, dried and unfortified — which gives a fair picture of what the yeast cell itself contains. Scaled from its per-100 g values to 10 g, it lists:

The RDAs above are the U.S. Institute of Medicine’s (Institute of Medicine 1998). Unfortified yeast is therefore a genuinely rich natural source of thiamine and folate, a moderate source of riboflavin and niacin, and not a source of vitamin B12.

What fortified labels declare

For fortified flakes, the best public source is the label data manufacturers submit to FoodData Central’s Branded Foods collection. We looked at eight plain, fortified nutritional yeast products listed there (label records published in 2023) and converted each label to a common 10 g amount. Ten grams is roughly two to three tablespoons of large flakes or about one tablespoon of powder: labels put a tablespoon at anywhere from about 3 g for large flakes to about 10 g for powder. Per 10 g, the eight labels declared:

Per labelled serving, which ranged from 5 g to 16 g, the same eight labels declared 17–70 mg of niacin, 1.7–13.6 mg of vitamin B6 and 2.2–60 µg of vitamin B12, and one product declared about 1,075 µg of folic acid in a quarter cup (15 g). Recipes change, and these are the manufacturers’ own declarations, so read the panel on the package you actually buy.

How to tell which you have: check the Nutrition Facts panel, not the front of the bag. If vitamin B12 is not listed on the panel, assume the product contains essentially none. Do not rely on the ingredient list alone: in USDA’s database, two products whose ingredients read only “dried yeast” or “inactive yeast” still declared B12 on the panel.

Evidence tier: food-composition data — USDA laboratory analysis for the unfortified yeast, manufacturers’ label declarations for fortified products.

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Vitamin B12: The Real Benefit, Only When Fortified

This is the benefit worth having, and it belongs to the fortified product alone. Vitamin B12 is needed to make healthy red blood cells and to keep nerves working. Running short causes a large-cell (megaloblastic) anaemia and nerve damage that can become serious and permanent if it is missed (Institute of Medicine 1998). Diets without animal foods are naturally low in B12 (Miller 2024), and yeast does not make meaningful amounts of its own — USDA’s analysis of dried yeast found only a trace. Fortified nutritional yeast, whose added B12 is often listed as cyanocobalamin, is one of a handful of fortified foods that can fill that gap without a pill.

The evidence

The only study we found that tested nutritional yeast itself for B12 status is small. Researchers measured 49 adults who had followed a mostly raw vegan diet for at least two years; most had followed it for two to four years. Three in four (37 people, 76%) had blood B12 below 221 pmol/L (300 pg/mL), and almost half (23 people, 47%) had raised urinary methylmalonic acid, a sign that their cells were already short of B12. When those with abnormal results were followed up, sublingual B12 tablets and nutritional yeast both significantly lowered the group’s methylmalonic acid; a probiotic supplement did not (Donaldson 2000). Because yeast carries essentially no B12 of its own, the improvement almost certainly came from B12 added to the yeast.

Evidence tier: a small, uncontrolled follow-up study — weak on its own, but it points the same way as the well-established physiology of B12 and the measured B12 content of fortified products.

What to do with this

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Protein and Amino Acids

Nutritional yeast is about half protein by weight. The plain products in USDA’s label data declared 40–60 g of protein per 100 g, which works out to about 3–5 g in two tablespoons of flakes and 5–8 g in a quarter cup.

The quality is good. USDA’s record for dried yeast (FDC 175043) lists all nine essential amino acids — the ones the body cannot make for itself — which is the everyday meaning of a “complete” protein. Per 100 g it lists 3.28 g of lysine, 2.92 g of leucine, 2.31 g of valine, 1.99 g of threonine, 1.89 g of isoleucine, 1.75 g of phenylalanine, 0.91 g of histidine, 0.59 g of methionine and 0.54 g of tryptophan. Lysine is the standout: it is the essential amino acid that grains run short of, so a sprinkle of yeast over brown rice or other whole grains complements them well. Methionine is present in much smaller amounts. More on lysine: Lysine.

Keep the amounts in perspective. At seasoning quantities, nutritional yeast adds a few grams of protein to a meal — useful, especially in plant-based cooking, but not a replacement for beans, eggs, fish or meat. Eating it by the quarter-cup to chase protein also runs straight into the purine and fortification limits described under Safety.

Evidence tier: food-composition data (USDA laboratory analysis and manufacturers’ labels), not outcome trials.

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Beta-Glucans, Immunity and Colds

Beta-glucans are long chains of glucose found in the cell walls of yeasts and mushrooms. Purified, insoluble beta-glucan extracted from yeast is sold as an immune supplement, on the proposed idea that immune cells lining the gut recognise the particles and are primed to respond faster to infection. What matters is what happened in people:

Two cautions keep these results in their place. First, both trials tested a purified extract in capsules, not nutritional yeast flakes, and we found no trial of nutritional yeast itself for colds. Whole yeast does carry beta-glucan in its cell walls, but we found no study measuring how much a tablespoon of flakes delivers, or whether the intact cell wall behaves in the body like the processed extract. Second, the trials disagree: a benefit in one, no change in the number of colds in the other, larger one.

Evidence tier: randomised controlled trials in humans of an isolated beta-glucan extract, with mixed results; nutritional yeast itself untested. For what does help with colds, see Common Cold. Oat beta-glucan is a different, soluble fibre studied mainly for cholesterol; see Oats for Beta-Glucan and Cholesterol.

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Nerves and Anxiety: What B Vitamins Can and Cannot Do

The popular videos say nutritional yeast “heals nerves” and “reduces anxiety.” There is a true version of that claim and a false one, and the difference is whether you are short of a B vitamin to begin with.

When you are deficient, B vitamins matter a great deal

Nerves and brain depend on B vitamins, and a real shortage shows. Lack of thiamine causes beriberi; lack of niacin causes pellagra, whose symptoms include mental changes; and lack of vitamin B12 damages nerves, sometimes permanently if it is missed (Institute of Medicine 1998). Correcting a genuine deficiency — with food, fortified food or a supplement — is effective medicine, and for a vegan the B12 in fortified yeast is a sensible way to prevent the problem in the first place. If you have numbness, tingling, balance trouble or unexplained low mood, the useful step is a blood test, not a bigger spoon; see Vitamin B12 Deficiency and Peripheral Neuropathy.

When you are not deficient, extra does little

The twist: too much B6 harms nerves

Vitamin B6 is the one B vitamin where more can damage the very nerves the videos promise to heal. Sensory neuropathy is the harm the U.S. upper limit of 100 mg a day is built on, and the first reported cases had taken 2,000 to 6,000 mg a day for months (Institute of Medicine 1998). A serving of fortified yeast will not get anywhere near that on its own, but people who stack a B-complex, a multivitamin and several spoonfuls of fortified flakes should add up their B6. See Vitamin B6 Toxicity.

Evidence tier: deficiency effects — established clinical medicine; extra B vitamins in people who are not deficient — systematic reviews showing little or no effect on anxiety or nerve damage; nutritional yeast itself — we found no trial for either claim.

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How to Use It

In the kitchen

How much

Choosing a product

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Myths and Overclaims in the Popular Videos

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Safety, Interactions and Who Should Avoid It

For most people, nutritional yeast in seasoning amounts is a safe food. The cautions below come from its purine content, from the doses of vitamins added to fortified products, and from a few specific medical conditions.

Gout, high uric acid and kidney stones

Yeast is rich in nucleic acids — roughly 5–8% of the biomass of most yeasts, and 8.1% RNA in one analysis of spent brewer’s yeast — and their purines are broken down in the body to uric acid (Jach 2022). Japanese researchers who measured purines in 270 foods found dried brewer’s yeast sold as a supplement at 2,995.7 mg per 100 g, in their highest category; chicken liver, for comparison, measured 312.2 mg. They advised people with gout or high uric acid to avoid such supplements, and noted that Japanese guidelines keep dietary purines below 400 mg a day (Kaneko 2014). Nutritional yeast itself was not in the study, but it is the same organism, dried whole; if its content is similar, a 10 g serving carries around 300 mg of purines. Reviews of yeast protein warn that high nucleic-acid intake can cause gout and kidney stones in people whose purine metabolism is impaired (Jach 2022). If you have gout, high uric acid or kidney stones, keep yeast to occasional pinches or skip it; see also Uric Acid Test.

Niacin flushing from fortified flakes

The U.S. upper limit for niacin added to foods or taken as supplements is 35 mg a day for adults. It was set because of flushing — a burning, tingling, itching sensation with redness, mainly on the face, arms and chest — seen at 50 mg a day. Flushing is temporary, but it can be alarming. It comes from nicotinic acid; the other form, nicotinamide, appears not to cause it (Institute of Medicine 1998). On U.S. ingredient lists, “niacin” means nicotinic acid and “niacinamide” means nicotinamide (21 CFR 184.1530), and the fortified products in USDA’s database that named their added vitamins all listed “niacin.” With 23–44 mg in 10 g, a generous helping can pass the adult limit on its own.

The limits for children and teenagers are lower: 10 mg a day (ages 1–3), 15 mg (4–8), 20 mg (9–13) and 30 mg (14–18). The Institute of Medicine also named people with liver disease, diabetes, active peptic ulcer, gout, heart-rhythm problems, inflammatory bowel disease, migraine or alcoholism as especially sensitive to excess niacin, and possibly not protected by the general limit (Institute of Medicine 1998). See Niacin Toxicity.

Folic acid is not the same as folate

Yeast naturally contains food folate — about 234 µg in 10 g of unfortified dried yeast. Fortified flakes add folic acid, the synthetic form, which is absorbed better: 1 µg of folic acid taken with food counts as 1.7 µg of dietary folate equivalents. The adult upper limit of 1,000 µg a day applies to folic acid from fortified foods and supplements, not to natural food folate (Institute of Medicine 1998). The fortified labels that listed folic acid separately declared 470–717 µg per 10 g, and one declared about 1,075 µg in a quarter cup — over the limit in a single serving.

The limit exists because large amounts of folic acid can correct the anaemia of vitamin B12 deficiency while the nerve damage carries on unnoticed (Institute of Medicine 1998). A 2024 review adds that people with low B12 and high folate have higher levels of homocysteine and methylmalonic acid (markers of B12 shortage) and lower cognitive test scores than people with low B12 alone, while stressing that this evidence is mostly correlational; it names people on vegan or vegetarian diets, older adults and people with B12 malabsorption as groups to watch (Miller 2024). Fortified nutritional yeast carries B12 as well as folic acid, so on its own it does not create that mismatch. The risk lies in combinations — for example, a vegan who uses unfortified flakes, takes folic-acid supplements and has no reliable B12 source. See Folate (Vitamin B9).

Crohn’s disease and anti-yeast antibodies

Many people with Crohn’s disease carry antibodies against mannan, a sugar on the cell wall of Saccharomyces cerevisiae; they are called ASCA (anti-Saccharomyces cerevisiae antibodies). In a study of stored blood samples from Israeli military recruits, ASCA were present in 10 of 32 people (31%) before their Crohn’s disease was diagnosed — on average 38 months earlier — and in none of 95 matched controls; after diagnosis, 54.5% were positive (Israeli 2005). What that does and does not mean:

A marker is not a cause, and there is no evidence that nutritional yeast harms people who do not have Crohn’s disease. If you do have it and notice that yeast-containing foods seem to worsen your symptoms, a trial without them is reasonable, ideally planned with your gastroenterologist or dietitian. See Crohn’s Disease.

MAOI antidepressants and tyramine

Older antidepressants called monoamine oxidase inhibitors (MAOIs) can cause a dangerous rise in blood pressure when combined with foods rich in tyramine. The yeast product with a well-documented warning is concentrated yeast extract, the dark spread: an evidence-based MAOI diet lists it among the few foods to avoid entirely, alongside aged cheese, aged or cured meats, sauerkraut, soy sauce and tap beer (Gardner 1996). Nutritional yeast is whole dried yeast, not an extract, and is not on that list, but we found no published measurement of its tyramine content. If you take an MAOI, ask your prescriber before using it regularly.

Yeast allergy

Some people are allergic to yeast proteins. Serious allergic reactions are reported only rarely, and people who regularly breathe in yeast are particularly at risk (Jach 2022). If yeast-containing foods have ever given you hives, swelling or breathing trouble, avoid nutritional yeast and ask about allergy testing.

Who should avoid it or take extra care

Evidence tier for the harms: food-composition analysis (purines), official intake limits (niacin, folic acid, vitamin B6), an antibody study and one small trial (Crohn’s disease), an evidence-based diet review (MAOIs) and a review statement (allergy) — enough to act on sensibly, without turning a seasoning into a hazard.

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Key Research Papers

  1. Bollet AJ (1992). Politics and pellagra: the epidemic of pellagra in the U.S. in the early twentieth century. The Yale Journal of Biology and Medicine. — PubMed PMID: 1285449
  2. Jach ME, Serefko A, Ziaja M, Kieliszek M (2022). Yeast Protein as an Easily Accessible Food Source. Metabolites. — PubMed PMID: 35050185
  3. Institute of Medicine (US) Standing Committee on the Scientific Evaluation of Dietary Reference Intakes and its Panel on Folate, Other B Vitamins, and Choline (1998). Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. National Academies Press (US). — PubMed PMID: 23193625
  4. Donaldson MS (2000). Metabolic vitamin B12 status on a mostly raw vegan diet with follow-up using tablets, nutritional yeast, or probiotic supplements. Annals of Nutrition & Metabolism. — PubMed PMID: 11146329
  5. Miller JW, Smith A, Troen AM, Mason JB, Jacques PF, Selhub J (2024). Excess Folic Acid and Vitamin B12 Deficiency: Clinical Implications? Food and Nutrition Bulletin. — PubMed PMID: 38987872
  6. Auinger A, Riede L, Bothe G, Busch R, Gruenwald J (2013). Yeast (1,3)-(1,6)-beta-glucan helps to maintain the body's defence against pathogens: a double-blind, randomized, placebo-controlled, multicentric study in healthy subjects. European Journal of Nutrition. — PubMed PMID: 23340963
  7. Dharsono T, Rudnicka K, Wilhelm M, Schoen C (2019). Effects of Yeast (1,3)-(1,6)-Beta-Glucan on Severity of Upper Respiratory Tract Infections: A Double-Blind, Randomized, Placebo-Controlled Study in Healthy Subjects. Journal of the American College of Nutrition. — PubMed PMID: 30198828
  8. Ang CD, Alviar MJ, Dans AL, Bautista-Velez GG, Villaruz-Sulit MV, Tan JJ, et al. (2008). Vitamin B for treating peripheral neuropathy. Cochrane Database of Systematic Reviews. — PubMed PMID: 18646107
  9. Young LM, Pipingas A, White DJ, Gauci S, Scholey A (2019). A Systematic Review and Meta-Analysis of B Vitamin Supplementation on Depressive Symptoms, Anxiety, and Stress: Effects on Healthy and 'At-Risk' Individuals. Nutrients. — PubMed PMID: 31527485
  10. Field DT, Cracknell RO, Eastwood JR, Scarfe P, Williams CM, Zheng Y, et al. (2022). High-dose Vitamin B6 supplementation reduces anxiety and strengthens visual surround suppression. Human Psychopharmacology. — PubMed PMID: 35851507
  11. Kaneko K, Aoyagi Y, Fukuuchi T, Inazawa K, Yamaoka N (2014). Total purine and purine base content of common foodstuffs for facilitating nutritional therapy for gout and hyperuricemia. Biological & Pharmaceutical Bulletin. — PubMed PMID: 24553148
  12. Israeli E, Grotto I, Gilburd B, Balicer RD, Goldin E, Wiik A, et al. (2005). Anti-Saccharomyces cerevisiae and antineutrophil cytoplasmic antibodies as predictors of inflammatory bowel disease. Gut. — PubMed PMID: 16099791
  13. Barclay GR, McKenzie H, Pennington J, Parratt D, Pennington CR (1992). The effect of dietary yeast on the activity of stable chronic Crohn's disease. Scandinavian Journal of Gastroenterology. — PubMed PMID: 1502481
  14. Gardner DM, Shulman KI, Walker SE, Tailor SA (1996). The making of a user friendly MAOI diet. The Journal of Clinical Psychiatry. — PubMed PMID: 8617704

PubMed Topic Searches

  1. PubMed: Nutritional yeast and vitamin B12
  2. PubMed: Yeast beta-glucan and colds
  3. PubMed: Anti-yeast antibodies (ASCA) and Crohn’s disease

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Connections

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