Recently, there have been reports that we aren’t getting enough vitamin D. In fact, it’s got so bad that in Cardiff, children have been getting rickets. So what should we do about it? How about eating mushrooms. That’s not such a crazy idea as you might think, as long as they’ve been on a tanning bed first.

We’re all taught that we make vitamin D using sunlight, and that’s certainly true. In fact, the 1928 Nobel Prize in chemistry was awarded to Adolf Otto Reinhold Windaus, in part for working out how cholersterol (it’s not all bad) is turned into vitamin D3 in the body. But as the BBC story I link to explains, not everyone is getting enough sun to make the vitamin D they need.


Luckily, we can also get vitamin D from our diets. These days, lots of foods are often ‘fortified’ with a huge array of vitamins and minerals, but there are also natural sources of vitamin D. These are mainly oily fishes like salmon, but mushrooms are also quite high in the vitamin, and suitable for vegetarians and vegans. And in a coup for those foragers among us, it seems wild mushrooms have more vitamin D than those cultivated mushrooms grown indoors. It seems mushrooms use sunlight to make the vitamin too.

Naturally this has led to the obvious question, can we just shine some UV on the mushrooms and get the same benefits? There have been quite a few papers on this and the answer seems to be yes. But if you’re wondering if this suspicious UV irradiation activity is a good idea, listen up, sometimes the lab is better than nature.

In this paper in J. Agric. Food Chem., button mushrooms were harvested and then either exposed to sunlight, or an equivalent dose of UVB (315nm–280nm), which I know as the wavelengths of UV that makes me go pink if I forget my suncream. While 100g of control mushrooms contained only 5μg of vitamin D, 100g of mushrooms exposed to sunlight contained 374μg of the vitamin and the same amount of UVB exposed mushrooms now had 410μg of vitamin D. That’s a lot more vitamin D than you’d get from the same amount of corn flakes (4.2μg).

So far so good. But if the vitamin D amounts for both groups of light exposed mushrooms are so high, why put your mushrooms on a tanning bed rather than giving them some fresh air and sunlight? Well the authors didn’t just measure the vit D concentrations in their mushrooms, they also measured the amounts of other vitamins and minerals present, and it seems sunlight isn’t so great after all. Although the sunlight helped make lots of vitamin D, it also reduced the amounts of riboflavin and folate. The authors suggest this might be because heat, or the more penetrating UVA in sunlight, caused the vitamins to degrade.

So, while tanning beds aren’t so healthy for humans, UVB exposure for your mushrooms is. However, I can’t help thinking that it would be better to just make sure everyone got enough sun in the first place, that at least is free.

Laura Howes

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