Vitamin D

Vitamin D plays an essential role in your overall health and a deficiency can have a negative impact. Learn what Vitamin D is and find how our nutrition plans and lifestyle advice can help you live a better life.

Approx read time: 3 mins

What is Vitamin D?

Vitamin D is really a hormone* – confusing, right? – and our bodies need it for building and maintaining healthy bones and supporting our natural immunity, amongst other things.

Vitamins are nutrients that we need to get from food because our bodies don’t make them, but food is a very poor source of vitamin D; instead our bodies make it in response to skin exposure to sunlight.

*hormones can be thought of as chemical messengers whereas a vitamin is a ‘nutrient’. 

What does it do?

Vitamin D, once made by the body, circulates in the blood and binds to special targets or ‘receptors’ on cells in order to cause certain critical actions.

One of the key actions is to ensure that calcium is absorbed via the gut and assimilated into bone.

But many cells and tissues other than bone and intestine have vitamin D receptors, including bone marrow, brain cells, hair follicles, cells lining the vagina, kidneys, pancreas, immune cells and more.

Vitamin D science is still very much emerging and more importance is being given to it almost by the hour!

What’s the problem?

Since so many people lead indoorsy lives and shy away from sun exposure, as well as not eating the very few foods that provide a bit of vitamin D, deficiency seems to be becoming more prevalent.

What about vitamin D and immunity?

In terms of immunity there have been some very good studies that show the importance of vitamin D to the immune system, particularly our ‘inborn’ or ‘innate’ immune system, where it activates certain types of immune cells that help to fight infections. 

Vitamin D deficiency has been linked to respiratory tract infections and its sufficiency linked to lack of the same, see here

Further research is needed and ongoing but there’s no harm in getting sufficient sunlight, without burning, to ensure adequate levels. 

Always remember that these things are not a replacement for clinical treatment and that levels of vitamins and minerals take time to reach their optimum. So banging down a load of supplements is not a treatment for anything.

Food and supplements

In terms of food, as I said above, there are low levels of vitamin D in certain foods such as oily fish, eggs, fortified margarines and some breakfast cereals, mushrooms that have been exposed to UV light and in vitamin supplements.

Getting vitamin D from food alone is not sufficient and if there is a lack of exposure to the sun or when the sunlight is weak, as in a UK winter, supplements might be beneficial. That’s something you should discuss with your GP but I would always recommend having levels tested before supplementing.

Is it a panacea?


Restoring low vitamin D levels to normal is not enough to promote good health in someone who doesn’t have other good health behaviours.

A nutritious diet, a healthy weight, getting enough sleep and activity, low alcohol consumption, no smoking and are all the other factors that need to work together to make a healthy individual.

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Thank you for reading this article. Please note that while we share a lot of awesome information and research you should be aware our articles are strictly for informational purposes and do not constitute medical advice intended to diagnose, cure, treat or prevent any disease.

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