Vitamin D From Mushrooms in the Sun: Khumbi Trick That Works
Yes. It works. Put sliced mushrooms gills-up in strong midday sun for 15 to 60 minutes and they make their own vitamin D, the way your skin does. The honest catch is that nobody can tell you how much you got, so sunned khumbi are a useful extra on the plate, not a fix for a low blood test.
Quick facts
- What happens: UV light turns ergosterol in the mushroom into vitamin D2
- Best time: about 10 am to 2 pm on a clear day, outdoors, not behind glass
- How long: 15 to 60 minutes, sliced, gills or cut side facing the sky
- Keeps: much of the vitamin D survives drying and a few months of dark, dry storage
- Not for: replacing a vitamin D test or the treatment a doctor prescribes
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How do mushrooms make vitamin D in the sun?
Your skin holds a cholesterol-like molecule that sunlight turns into vitamin D3, and mushrooms hold a close cousin of it, called ergosterol, packed mostly into the thin papery gills under the cap and the soft skin on top. Same trick. Different organism.
When UVB rays (the short, burning part of sunlight) hit ergosterol, the ring in the middle of the molecule snaps open, and a little later the result settles into vitamin D2 (ergocalciferol), which your body can use once you eat it. Mushrooms grown in dark sheds, which is most button mushrooms in the market, have almost none. A sunbath changes that.
Wild mushrooms that grew under the open sky often carry some already. Please don’t go picking wild ones for this reason; some deadly species look ordinary, as our guide to buying and storing khumbi explains.
A mushroom is a tiny solar panel that stores vitamin D instead of electricity.
How to sun mushrooms for vitamin D: step by step
- Pick the day: clear sky, between roughly 10 am and 2 pm. In Pakistan and north India, summer and early autumn give the strongest UVB, while winter mornings and the hazy, smoggy days of November in Lahore or Delhi give much less, even when the sun looks bright.
- Prepare 200 to 250 g mushrooms: wipe with a damp cloth or rinse fast and pat dry. Slice about 0.5 cm thick, or turn whole mushrooms gills-up. More exposed surface means more vitamin D.
- Lay them out in one layer: on a clean steel thali or tray, not overlapping.
- Put them in direct sun outdoors: a roof, balcony or courtyard. Glass blocks UVB. A windowsill won’t do.
- Leave 15 to 60 minutes: 15 to 30 minutes in fierce summer sun, up to an hour in milder weather. Net them if flies come.
- Cook or chill within 2 hours: fresh mushrooms spoil fast when warm. Refrigerate in a paper bag. Use within 2 days.
Dry them for later
Leave thin slices in the sun for 1 to 2 full days, bringing them in at night, until they snap rather than bend. Store in a dry, airtight jar in a dark cupboard and use within about 6 months, throwing out anything that has turned soft, damp or musty, because mould on dried food can make toxins you can’t cook away. Soak 10 minutes in warm water and add to pulao, soup or a mushroom-matar sabzi.
How much vitamin D do sunned mushrooms really give?
Honestly? It varies. A lot. The amount depends on the strength of the sun, the minutes, the thickness of the slices, the variety and how you cook them afterwards.
Mushrooms sold as UV-treated in some countries are zapped under lamps to a set level and can supply a day’s worth in a normal serving. Home sunning can reach a meaningful amount too, but you have no way to measure it in your kitchen. For reference, the usual daily need for adults under 70 is 600 IU (15 micrograms), and 800 IU over 70.
D2 is also a little weaker than D3 over time. Think of a sunned mushroom sabzi as a helpful top-up alongside eggs, oily fish, fortified milk and sensible sun on your own skin, which our vitamin D and sun exposure guide covers in detail.
Does cooking destroy the vitamin D?
Some, not most. Vitamin D is fairly heat-stable, and because it dissolves in fat rather than water, very little of it leaks out into a pan of bhuna masala the way water-soluble vitamins leak into boiling water.
- A quick stir-fry or bhuna in a little oil keeps a good share.
- Long boiling in water you then throw away loses more.
- Cooking with a little ghee or oil also helps your body absorb it, because vitamin D travels with fat.
Add them late to a curry. Or sauté them with garlic and black pepper for 5 minutes and fold into an omelette.
Myth: any sunlight on any mushroom does the job
Three things break the trick. Glass blocks UVB. Indoors behind a window gives little. Early morning and late afternoon sun carry very little UVB. And stacking whole mushrooms cap-up in a basket exposes only the tops, while the gills, which hold much of the ergosterol, stay in the dark. Slice. Spread. Go outside at midday.
Bone pain, muscle weakness, frequent cramps or a child with bowed legs or slow growth need a doctor and a blood test, not a kitchen experiment. If a report shows low vitamin D, follow the treatment your doctor prescribes and don’t swap it for mushrooms; our guide to reading a vitamin D report explains the numbers. People with kidney disease, sarcoidosis or high calcium levels should ask before adding extra vitamin D from any source. Only ever sun mushrooms bought from a shop or grown from a known kit.
Sunned mushroom questions people ask
Can you get vitamin D from mushrooms kept in the sun?
Yes. Sunlight turns their ergosterol into vitamin D2, which your body can use, although the amount swings so widely with the strength of the sun, the minutes and the slicing that nobody can measure it in an ordinary home kitchen.
How long should mushrooms be kept in sunlight?
About 15 to 60 minutes of direct midday sun, sliced and gills up. Shorter in harsh summer sun, longer in mild weather.
Should mushrooms be gills up or down in the sun?
Gills up. Or sliced, cut faces up. The gills and cut surfaces expose more ergosterol to the UV light.
Does sunlight through a window work?
Barely. Ordinary glass blocks most UVB, which is the part of sunlight that makes vitamin D.
Do button mushrooms have vitamin D?
Almost none, if farmed in the dark. A short sunbath before cooking gives them some.
Can sun-dried mushrooms keep their vitamin D?
Yes, much of it survives drying and a few months in a dark, dry, airtight jar. Light and damp reduce it over time.
Is mushroom vitamin D as good as sunlight on skin?
Close, not equal. Treat it as a top-up, not the main source.
Can sunned mushrooms fix vitamin D deficiency?
No. A diagnosed deficiency needs the treatment your doctor prescribes. Mushrooms can help keep intake up once levels are back to normal.
Is it safe to leave mushrooms outside?
For an hour, yes. Use a clean covered tray, then cook or refrigerate them within 2 hours, or dry them fully before storing.
Can children eat sunned mushrooms?
Yes, well cooked and cut small for young children. Sunning doesn’t change their safety, only their vitamin D.
For more on what light, heat and water really do to food, see Kitchen Science, Honestly.