Vitamin D is unique among the vitamins in that the cholesterol naturally present in our skin can make vitamin D from sunlight, so We don’t just need to get it from our diets. this is why it’s often known as the sunshine vitamin.
In fact, vitamin D acts more like a hormone than a vitamin as it can tell the body to carry out actions at a distance.
Vitamin D’s major function is helping to balance levels of calcium and phosphorus in the body, vital for creating strong, healthy bones and teeth. There is also increasing evidence to suggest D plays other important roles in the body and immune system – from reducing the risk of cancers, to helping prevent cardiovascular disease (CVD), infectious diseases and autoimmune diseases. Much more research is needed to confirm the role D may play in these other areas, however.
What’s the story?
New research is emerging all the time about vitamin D, to the extent that it was only in 2016 that SACN (the expert advisory committee for nutrition in the UK) felt that there was sufficient evidence to recommend an RNI for the adult population. Previously, it wasn’t thought necessary. For an entertaining and ever-so-slightly bonkers video about the new and emerging evidence around D, take a look at this talk here.
Vitamin D is also a perfect example of why supplements can be more trouble than they’re worth. The body has a clever inbuilt mechanism that stops too much active vitamin D being produced from sunlight, as it’s the liver and kidneys that convert vitamin D into its active form. No such mechanism exists however with supplements, so be careful not to take excessive amounts in supplement form.
How much do I need?
For adult men and women (including those over 50 years old and anyone pregnant), you need 10 μg (micrograms) per day.
Where can I find good sources?
It’s difficult to get enough from food sources alone. Oily fish such as salmon, mackerel, and sardines are good sources, as are egg yolks, butter, cod liver oil (sorry) and liver. Some breakfast cereals and breads are also fortified with vitamin D; useful if for some strange reason your 5-year old doesn’t fancy a portion of liver for dinner…. Interestingly enough, mushrooms can be a good source of vitamin D when exposed to UV light, so next time you buy some mushrooms try leaving them on the window sill for a couple of hours.
But the best way of getting enough vitamin D is to spend 5-30 minutes in the sun at least twice a week, between 10 am and 3 pm, exposing your face, arms, legs or back. Be warned that sun block of 8 SPF+ or wearing lots of clothing will prevent the sun getting to your skin in adequate amounts, and in countries on a more northern latitude such as the UK, we don’t get enough sun during the winter months (October to March) to make enough D. So although not by any means necessary for most vitamins and minerals, a supplement of 10 μg every day is recommended in the UK when it comes to Vitamin D.
Any ideas for using those ingredients?
Salmon with miso veg stirfry/shakshuka/lentil, mushroom and hazelnut/liver alla veneziana/trout with avocado and pumpkin seeds/mackerel with black olives, capers and tomato/sardine and apple salad
References
Keegan, RJ., Lu, Z., Bogusz, J.M., Williams, J.E., Holick, M. F. (2013) Photobiology of vitamin D in mushrooms and its bioavailability in humans. Dermatoendocrinol. v. 5 (1), pp. 165–176. Available here
Public Health England (2016) The Scientific Advisory Committee on Nutrition (SACN) recommendations on vitamin D. Available here.
Price, C. (2016) The Vitamin Complex. London, Oneworld Publications, pp. 263-4.