The Facts at glance
Vitamin D from Sunlight
Mushrooms exposed to sunlight naturally generate vitamin D
UV light exposure
Some producers expose mushrooms to a burst of UV light after harvesting. One serve of these mushrooms generates your daily need of vitamin D
One hour of sun
100g of mushrooms in the winter sun for an hour will generate your daily needs of vitamin D
Vitamin D & Mushrooms
Mushrooms naturally produce vitamin D when they see sunlight (or another source of UV light). Through the action of sunlight, they convert their abundant ergosterol to ergocalciferol (vitamin D2). Wild mushrooms in Europe commonly have 2-40 mcg vitamin D/100g.
Farmers generally don’t subject their mushrooms to light other than during growing operations and harvesting, however mushrooms from retail stores can have 1-5 mcg vitamin D per 100g, possibly due to UV light exposure in-store (University of Sydney analysis 2013, unpublished). An analysis in 2015 of mushrooms from five cities undertaken by the National Measurement Institute confirmed an average 2.3 mcg vitamin D per 100g, which is 23% of daily needs.
Store-bought mushrooms are able to generate over 20 mcg per serve after being placed in sunlight for a couple of hours in the sun for about an hour produced about 10 mcg of vitamin D in a 100g serve.
If the mushrooms are exposed to a short burst of ultraviolet light after harvesting they quickly generate vitamin D, while retaining the good looks and nutrition of the mushroom. Once consumed, the vitamin D2 in mushrooms is converted to 1, 25 (OH) ergocalciferol. Both vitamin D2 and D3 act in the same way in the body.