Mrs Growster has just discovered that if you leave any mushrooms - shop or field, in a sunny position for a while, they just absorb the light and create huge amounts of Vitamin D, and then become a great way to back-up and restore levels in the human body!
We've never heard of this, as I've never had any success with them, but as they grow in darkness, they presumably want to catch up!
Seems to make sense, and worth remembering in the winter months!