No I haven’t gone crazy! It’s usually myself going out in the sunshine to get some Vitamin D – not my food! In the last week the sun has finally decided to show itself and give a little glimpse of summer so I thought it would be the perfect time to talk about Vitamin D and a relatively novel way of how to get it.
Vitamin D is a pretty hot topic. Most people know that our skin produces it upon exposure to sunlight and that some foods contain small amounts, but did you know that mushrooms are able to produce vitamin D in a similar format when exposed to ultraviolet light? This is great news for vegetarians because it is obviously a completely vegetarian AND vegan source of vitamin D – many products fortified with vitamin D are from animal origin making them unsuitable.
Mushrooms are naturally rich in ergosterol (pro-vitamin D). The action of sunlight (or UV light) on the surface of the mushrooms changes the pro-vitamin D to ergocalciferol (vitamin D2). European wild mushrooms have been found to contain between 2-40mcg vitamin D/100g.
Wild mushrooms and sun dried mushrooms often used in Asian cooking naturally contain higher vitamin D because of natural sun exposure. But it even works for store-bought mushrooms – typically the common button mushroom. Just put your mushrooms in the sun like I did anytime between 10am and 3pm for between 30-60 minutes and you will be naturally eating an additional source of Vitamin D. If you place the mushrooms upside down so the gills (the brown bit underneath) are facing upwards they will create an even greater amount of Vitamin D. I forgot to do that this time though!
The content of vitamin D that can develop in mushrooms varies from species to species and it varies according to where, how and when they are exposed to the sunlight or artificial UV light. Shiitake mushrooms are probably one of the highest sources. One researcher found that shiitake mushrooms that had been grown inside increased their vitamin D content from 110 IU (international Units) to a massive 46,000 IU after being put outside in the sun for 6 hours gills facing up. When the gills faced down it rose to 10,900 which is still impressive in itself.
Mushrooms grow very quickly and artificial UV exposure during the growing phase can end up with a diluted effect if not exposed repeatedly. Last year Kristensen et al published a study looking at how different methods of UV-B exposure impacted the end vitamin D content. Exposure just before or after harvest resulted in the greatest vitamin D2 with post harvest exposure to UV-B resulted in 32mcg/100g vitamin D2 in fresh button mushrooms.
There has been much debate over the years about which of the two kinds of Vitamin D – D2 and D3 – are better for improving your serum or blood vitamin D levels. A study recently published (Keegan 2013) looked at whether vitamin D2 in dried mushroom extract was as effective in increasing and maintaining vitamin D status as supplemental vitamin D2 and vitamin D3.
Thirty adults were randomised to receive either 2000 IU mushroom extract vitamin d2, 2000 IU vitamin D2 or 2000 IU vitamin D3. After the 12 week study was completed there was no statistical difference between the serum vitamin D levels between each group demonstrating that eating mushrooms containing vitamin D was as effective as supplemental vitamin D2 or D3. The table below shows the changes in total serum vitamin D levels in each group at the beginning and end of the study.
|Group||Baseline ng/mL||12 weeks ng/mL||Significance|
|Total serum 25(OH)D levels||mushroom extract||20.6||30.1||p < 0.001|
|vitamin d2 supplement||19.4||29.2||p < 0.01|
|vitamin d3 supplement||17.1||34.4||p < 0.05|
Mushroom manufacturers in Australia, the USA and Canada are now selling vitamin D rich mushrooms in the supermarkets and I would imagine other countries will swiftly follow suit. I think it will be interesting to see how this contributes nutritionally to overall vitamin D intakes and whether increasing general awareness of mushrooms being a source of vitamin D can help to improve vitamin D deficiencies in the coming years.
Hopefully this has given you some new insight about vitamin D in mushrooms and maybe you can join me by putting your mushrooms in the sun for better health!
Enjoy the sun!
- Kristensen, Rosenqvist, Jakobsen (2012) Increase in vitamin D2 by UV-B exposure during the growth phase of white button mushroom (Agaricus bosporus) Food and Nutrition Research Vol 56:7114
- Keegan, Lu, Bogusz, Williams, Holick (2013) Photobiology of vitamin D in mushrooms and its bioavailability in humans. Dermato-Endocrinology 5(1)