Mushrooms and vitamin D
Mushrooms can produce vitamin D after exposure to ultraviolet light. Here is what that means for labels, preparation and your diet.
Mushrooms are unusual among plant-forward foods because they contain ergosterol, a compound that can be converted into vitamin D when exposed to ultraviolet light. The process resembles the way human skin makes vitamin D after sunlight exposure. Mushrooms grown indoors in darkness generally contain little vitamin D unless producers treat them with UV light.
Wild varieties may contain more vitamin D because they receive sunlight, but the amount can vary considerably. Some commercial growers expose mushrooms to UV light during or after cultivation. Packages may identify them as “UV-treated” or state a vitamin D amount on the Nutrition Facts label.
What to check on the package
Look for a specific vitamin D value on the Nutrition Facts panel. The word “mushrooms” alone does not indicate a meaningful amount because variety, growing conditions, UV exposure and storage can all influence the final level.
Vitamin D2 versus vitamin D3
Mushrooms make vitamin D2. Vitamin D3 occurs naturally in a small number of animal-derived foods and is also commonly used in fortified products and supplements. Both forms can raise vitamin D status, though research suggests D3 may maintain levels more effectively in some circumstances. The practical choice depends on diet, dose and individual health needs.
Vitamin D2 is not animal-derived, which may matter to people following vegetarian or vegan diets. Supplement ingredients can differ, so anyone choosing a product for dietary reasons should read its label carefully.
Can sunlight increase vitamin D in mushrooms?
Research has shown that exposing mushrooms to UV light can increase their vitamin D content. Sliced mushrooms and mushrooms positioned with their gills toward the light expose more surface area. However, results at home are difficult to predict because sunlight intensity, season, cloud cover, time and mushroom type all vary.
Vitamin D produced before cooking is generally retained to a useful degree, although storage and cooking method can affect the final amount. For dependable dietary tracking, packaged UV-treated mushrooms with a declared vitamin D value are more practical than estimating the effect of home sun exposure.
How to use them
UV-treated mushrooms can be prepared like other mushrooms: roast them, sauté them, add them to soups, or use them to bring savory flavor to grain and vegetable dishes. For more ideas, see this guide to mushrooms as a source of umami.
Test your knowledge: Vitamin D: How Much Do You Know?
This article provides general educational information. Vitamin D needs can vary with age, diet, health conditions, medications and sun exposure; it does not replace individual medical advice.
