Vitamin D has got a lot of press in the last year, for good reason! It's key to supporting a healthy immune system, and an easy one to miss out on in the UK. We all want to know how we can get more of it.
The government recommendations remind us it is essential to find good natural sources of Vitamin D all year and to support them with supplements over the winter months (Oct-Apr). During the summer months, we can produce vitamin D from sunshine.
But did you know you can get some of your vitamin D from food sources? While salmon and eggs are the classic examples and are certainly good ones, there is a surprising plant source of vitamin D that's often overlooked, too: mushrooms.
Mushrooms contain a range of nutrients including B vitamins, minerals, antioxidants and fibre – another important nutrient for immune health. But their vitamin D content is unique amongst the plant world.
We asked Dr Glenys Jones from the Association for Nutrition to explain how mushrooms can help support our immune systems through their vitamin D content, and how to tell which mushrooms are best to get hold of, as well as tips for boosting any mushroom's vitamin D levels.
Mushrooms are one of the few foods that naturally contain vitamin D, but the content will vary dramatically depending on how they are grown, so make sure you check your mushroom sources.
If they are grown in the dark, then they will have low levels of vitamin D present and cannot be considered a source of vitamin D. However many varieties readily available in the supermarket now have little pings on their packaging to let you know that they have enhanced/high vitamin D levels and these can be classed as a source of vitamin D.
This enhanced level of vitamin D is achieved by either growing the mushrooms outdoors in the light or being moved outside for their last few days. The other (more popular method) is to shine a UV light source on them in the factory during packing.
Research from the USDA has shown that 100g of mushrooms that have been exposed to UV light, can go from containing 0.1-0.7mcg of vitamin D (3-29iu) to containing 13.1-31.9mcg (524-1276iu)! This shows us that the enhanced level of vitamin D in mushrooms exposed to UV light means that a portion of these mushrooms ( e.g. 4-5 chestnut mushrooms or a large portobello mushroom, or 80g) can provide us with a delicious source of our daily recommended intake of vitamin D (10mcg / 400iu).
We can easily achieve a similar thing at home, by placing our portion of mushrooms in the light on the windowsill or out in the garden/balcony for about an hour (ideally between 11am & 3pm when the sun is at its highest, and best March-Sept time). Whilst the levels we achieve will vary depending on the level of UV light there is on that day, the mushrooms will behave very similar to ourselves when our skin is exposed to spring or summer sun, and they will absorb the UV light and use this to naturally produce more vitamin D and can therefore become a good source of vitamin D in our diet.