Scientists claim mushrooms are vit D factories

But there's a catch. Like humans, button mushrooms need exposure to sunlight for the photochemical manufacturing to kick into action.

Button mushrooms need two hours unwrapped on a plate in the midday summer sun – a bit longer in winter – to get the vitamin D boost, said Professor Rebecca Mason, head of physiology at Sydney Medical School, who assisted with the research. 

Placing the mushrooms a couple of extra hours in the shade will allow time for the full chemical reaction, she said. 

This step doesn't affect the mushroom or the taste either.

The research investigated the vitamin D levels of three standard button mushrooms exposed to direct midday sunlight.

Results confirmed they generate vitamin D levels in a similar way to humans and an average serve of 100g or three button mushrooms can provide 100% of an adult's daily requirement (10mcg). 

Professor Mason said this amount is enough