Okay, before you decide I'm crazy give me a second to explain. This is such an interesting fact that I forget about, then remember and become so excited by every time, hence this post.
While it's well known that mushrooms are super nutritious, providing fibre, B vitamins and selenium, potassium, copper and zinc, they also provide some vitamin D. Typically, 5 white button mushrooms would provide 1-3ug of vitamin D. Our daily requirements are 5-15ug and we are to get most of this from the sun. Well, so can mushrooms! Despite being classified as a vegetable food-wise, mushroom are fungi. They contain pre-vitamin D (initially ergosterol) in their cell walls, similar to what is found in our skin. When exposed to sunlight, this becomes vitamin D! For example, if you charge up those 5 button mushrooms in the sun over midday, they have been found to then provide at least 10ug, and up to 32ug. If left in the sun for 2 hours, this would be more than our daily requirement and equivalent to supplementary doses (1000IU as it is normally labelled). Isn't this cool? If the mushrooms are sliced and have more surface area, the number was found to be higher. It isn't only button mushrooms either- same goes for 3 cup mushrooms or 1 portabella. Additionally, this vitamin D has been found to be bioavailable (used by the body), lasting up to a week in the fridge and to withstand heat quite well (>60% retained, higher with certain methods). Now, I bet you're just as excited about this as I am. I expect to see all your mushies sun baking from now on! . 🐶 Keep them out of reach of pets!
A nice, clear summary can be found here: