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Moderate evidenceVitamins & minerals

Nutritional Yeast

A genuinely useful food: deactivated Saccharomyces cerevisiae that delivers complete protein, fibre and — if fortified — a reliable vegan source of B12 and other B vitamins. Its value depends almost entirely on whether the label says fortified.

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What the science says

  • Fortified nutritional yeast is a reliable vegan B12 source Strong evidence

    This is the strongest claim in the entry and it is a labelling issue, not a biology one. Fortified nutritional yeast has cyanocobalamin added during production; a typical 2 tablespoon (16 g) serving supplies 5-20 mcg of B12, far above the 2.4 mcg RDA. Unfortified yeast contains negligible active B12 — analyses of plant and fungal foods confirm that yeasts do not synthesize cobalamin, and several 'natural' B12 sources contain inactive corrinoid analogues instead. Check the supplement facts panel.

  • Provides high-quality complete protein Moderate evidence

    Nutritional yeast is roughly 45-50% protein by dry weight and contains all nine essential amino acids, including a decent lysine content that complements grain-based diets. A 16 g serving gives about 8 g protein and 4-5 g fibre for around 60 calories. Useful as a seasoning that carries nutrition, though nobody eats enough of it to be a primary protein source.

  • Yeast beta-glucan supports immune function Moderate evidence

    Nutritional yeast contains beta-glucan and alpha-mannan cell wall components. A systematic review and meta-analysis of yeast beta-glucan supplementation in healthy adults found reduced upper respiratory infection incidence and symptom scores at 250-500 mg/day of the purified compound over 8-12 weeks. Whole nutritional yeast is not standardized for beta-glucan, so the food form has not been tested for this outcome.

  • Is a replacement for a full B-complex or multivitamin Limited evidence

    Fortified varieties cover B1, B2, B3, B6, folate and B12 well, but the fortification blend differs by brand and it provides no vitamin D, no iron in useful amounts, no omega-3 and no calcium. Treat it as a strong B-vitamin food, not a multivitamin.

Dosage & safety

Studied doseA standard serving is 2 tablespoons (about 16 g), typically supplying 8 g protein, 4-5 g fibre and — when fortified — 5-20 mcg B12, plus 100-700% of the RDA for several other B vitamins. One serving per day is a reasonable habit for vegans relying on it for B12; those with B12 deficiency or malabsorption need a dedicated supplement (typically 250-1000 mcg/day) rather than a food source.
SafetyWell tolerated as a food. Some people get gas or bloating from the fibre. Contains tyramine — relevant for MAO inhibitor users and, anecdotally, for migraine sufferers sensitive to aged and fermented foods. High purine content means caution with gout. People with Crohn's disease often have elevated anti-Saccharomyces cerevisiae antibodies and some report symptom flares. Rare yeast allergy exists. Because it is deactivated, it does not carry the fungemia risk associated with live yeast preparations in immunocompromised patients. Heavy reliance on fortified yeast for B12 requires the fortification to actually be there — several brands sell unfortified 'natural' versions that are not adequate B12 sources.

How to take it

TimingTiming does not matter.
With food?It is a food — sprinkle it over meals.
Worth knowingConfirm the label says fortified with B12; several brands sell unfortified versions that are not adequate B12 sources for a vegan diet.

Interactions

With medications

  • MAO inhibitors (phenelzine, tranylcypromine, selegiline) and linezolid

    tyramine in yeast can trigger a hypertensive reaction avoid it on an MAOI, as you would aged cheese and fermented foods

With other supplements

  • B12 supplements

    a fortified serving can supply a full daily B12 dose, but unfortified 'natural' versions supply essentially none check the panel before dropping a separate B12, and keep the supplement if you have deficiency or malabsorption

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

Is nutritional yeast a good source of B12?

Only if it is fortified. Fortified nutritional yeast is a reliable vegan B12 source, with a 2 tablespoon (16 g) serving typically supplying 5-20 mcg of B12, but unfortified versions contain negligible active B12, so check the label.

How much protein is in nutritional yeast?

A 16 g serving of nutritional yeast gives about 8 g of complete protein and 4-5 g of fibre for around 60 calories. It is a useful seasoning that carries nutrition, not a primary protein source.

Can nutritional yeast replace a multivitamin?

No. Fortified nutritional yeast covers several B vitamins well, but it provides no vitamin D, no useful iron, no omega-3 and no calcium. People with B12 deficiency or malabsorption need a dedicated supplement rather than a food source.

Does nutritional yeast have side effects?

Nutritional yeast is well tolerated as a food, though the fibre can cause gas or bloating. It contains tyramine, so avoid it on MAO inhibitors, and its high purine content calls for caution with gout.

Scientific references

Where to buy

NuNaturals, Non-Fortified Nutritional Yeast Flakes, 1.5 lb (681 g)

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