WAIT… MUSHROOMS CAN ACTUALLY MAKE MORE VITAMIN D AFTER YOU BUY THEM?!
Saturday, 17 October 2026 • NOBODY TELLS YOU THIS
Q: Can exposing mushrooms to sunlight increase their vitamin D content?
A: Yes. UVB light can convert ergosterol in certain edible mushrooms into vitamin D₂, including after harvesting. Actual amounts depend greatly on the mushroom and exposure conditions.
HOW DOES A MUSHROOM DO THAT?
Mushrooms contain ergosterol, which reacts with suitable UV radiation. This is the basis for commercially UV-treated mushrooms and research testing sunlight exposure. It is not the same as saying every mushroom from the supermarket is high in vitamin D.
WHAT THE STUDIES FOUND
A 2018 review described experiments where sliced mushrooms in sufficiently strong sunshine produced nutritionally relevant vitamin D₂; the results varied by season, latitude, species and exposure time. A separate cooking study reported high vitamin D retention under its tested cooking conditions for UV-treated dried mushrooms.
HOW TO SHOP SMARTER
Look for labelled UV-treated or vitamin-D mushrooms and use declared nutrition information when available. Normal windows may block much of the UVB needed, so a kitchen windowsill is not a reliable vitamin-D production method.
WHAT ABOUT TRYING IT AT HOME?
If experimenting with ordinary edible shop-bought mushrooms and outdoor sunlight, use a clean food-safe tray, protect from insects and contamination, and do not leave perishable food at unsafe temperatures. Don’t use improvised UV lamps or copy controlled industrial treatments.
IMPORTANT LIMITS
Vitamin D₂ is not identical to vitamin D₃ in every outcome. Mushrooms are not a guaranteed substitute for prescribed supplementation, and wild mushrooms must never be eaten without correct expert identification.
MY TAKEAWAY
A little light can change the chemistry of something we think of as an ordinary ingredient. That’s the kind of kitchen science I love — with the caveat that the vitamin label beats guesswork.
AVAILABILITY, COST & LIMITATIONS
UV-treated labelled products vary by market and cost; sunlight result unpredictable.
OFFICIAL / RESEARCH SOURCES
https://pmc.ncbi.nlm.nih.gov/articles/PMC6213178/
https://pubmed.ncbi.nlm.nih.gov/37224637/
https://data.food.gov.uk/regulated-products/novel_authorisations/novel-144