Ergosterol

Fatty-acidSterolBest with a meal

What is it

Ergosterol is a sterol found in fungi (yeast, mushrooms) and some protists. It is the biological precursor of vitamin D2 (ergocalciferol), which forms when ergosterol is exposed to ultraviolet light.

Evidence for 1 use

AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.

Vitamin D2 precursor

Good Evidence

Ergosterol converts to vitamin D2 with UV light. UV-exposed mushrooms can meaningfully raise vitamin D levels in deficient individuals.

How it works

When fungal-source ergosterol is irradiated with UV-B light, it converts to ergocalciferol (vitamin D2). UV-exposed mushrooms are a meaningful dietary source of vitamin D2. Ergosterol itself has a structural role in fungal cell membranes (similar to cholesterol in animal cells) and is the target of antifungal medications like the azoles, which inhibit its synthesis.

Dosage

There is no RDA for ergosterol; it is generally consumed indirectly through mushrooms and as a precursor to vitamin D2.

When and how to take it

Eat mushrooms (especially UV-exposed) at any meal. For vitamin D2 supplementation, take with a meal containing some fat for better absorption.

1 commercial form

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Mushroom-derived ergosterol

Found in many edible mushrooms; concentration enhanced by UV treatment.

Converted to vitamin D2 with UV exposure

Safety

Ergosterol from food sources is considered safe. Vitamin D2 derived from it has an established safety profile up to the tolerable upper intake limit (4,000 IU/day for adults).

Who should be cautious

Generally safe in pregnancy and breastfeeding at food levels. Vitamin D status should be discussed with a clinician for supplementation.

Interactions

No significant interactions from dietary ergosterol. Vitamin D2 derived from ergosterol interacts with other vitamin D forms in cumulative intake.

Food sources

UV-exposed maitake mushrooms

Amount
1/2 cup
%DV
—

Sun-dried shiitake mushrooms

Amount
1/2 cup
%DV
—

Frequently asked questions

Do all mushrooms provide vitamin D?⌄

Mushrooms contain ergosterol but need UV exposure (sunlight or commercial UV treatment) to convert significant amounts to vitamin D2.

Is vitamin D2 as good as D3?⌄

Both raise blood vitamin D levels. D3 is generally more efficient per dose, especially at higher doses.

References

Ergosterol on Wikidata — Wikidata link

Ergosterol (ChEBI:16933) — ChEBI link

Ergosterol (PubChem CID 444679) — PubChem link

Ergosterol on NIH DSLD (US supplement label database) — NIH Dietary Supplement Label Database link

Research on Ergosterol (PubMed search) — PubMed link

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Evidence-based·How we grade evidence

Disclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you’re pregnant, breastfeeding, on medications, or managing a chronic condition.