As we enter the Autumn and Winter months of the year, we lose our natural ability to make vitamin D from skin exposure to sunlight. We therefore should be looking at alternative ways to maintain our vitamin D status through our diets. I have previously written about the importance of supplementation during winter months, but there are alternative sources to supplementation if you further want to ensure your vitamin D status remains within the healthy range during the darker days.
Sun-dried and UVB irradiated mushrooms are the only non-animal-based food product with substantial amounts of bioavailable vitamin D (as D2) and, as such, have the potential to be a primary source of vitamin D in a vegetarian and vegan diet.
Most fresh-grown retail mushrooms in the UK are grown in dark, temperature-controlled rooms before being refrigerated and transported. Thus, the vitamin D2 content of most mushrooms sold is commonly less than 1μg/100g fresh weight (FW), and therefore the typical serving of mushrooms is negligible.
When mushrooms are exposed to midday sunlight for 15-120 minutes they will generate significant amounts of vitamin D2 (<10μg/100g FW) which approaches the recommendation for the UK which is set at 10μg/day. However, the total amount of vitamin D generated in these mushrooms is dependent on many factors, such as length of exposure, time of exposure, the surface area exposed, and weather. Increasing the surface area by slicing the mushrooms to expose more flesh can increase vitamin D production. Additionally, certain species of mushrooms will produce more vitamin D if the gills are exposed.
Commercially produced vitamin D mushrooms are exposed to specific UV radiation in the growing and/or post-harvest phase. Fresh mushrooms deliberately exposed to UV light post-harvest can produce vitamin D2 levels up to 320μg/100 FW (calculated from dried weight).
In contrast, wild mushrooms are naturally exposed to UV light and therefore contain vitamin D2, as are sun-dried mushrooms. Both wild and sun-dried mushrooms contain significant amounts of vitamin D2.
There are plenty of mushroom-containing recipes available on my website which can easily use vitamin D-enriched mushrooms, but here are a few of my favourite!
- One of my favourite foods Mushroom Risotto
- My vegan Mushroom & Lentil Pie
- Reduced Meat Bolognese with added vitamin D
- Super creamy Roasted Mushroom Pate