If there was a title for ‘nutrient of the year’ (thankfully there doesn’t seem to be), vitamin D would undoubtedly triumph as it’s rarely been out of the press in recent months.

So why are we suddenly hearing so much about this vitamin, and should we believe the hype?

What does vitamin D do?

The main role of vitamin D is to help the body absorb calcium for strong, healthy bones and teeth. It’s unusual among the vitamins in that we’ve evolved to produce vitamin D from sunlight. Cholesterol in our skin, followed by a series of reactions in the liver and kidneys, converts sunlight into the active vitamin. We can also get it from a few foods (notably oily fish), but not all that many. After Steenbok figured out how to get rid of rickets (where children's bones don't develop properly due to a lack of D) and patented his discovery in the 1920’s however, we sort of forgot about this vitamin a little bit.

So what’s suddenly changed?

New and emerging evidence over the past few years has indicated that;

a) most of us are probably not getting enough of it, and

b) vitamin D may actually play a bigger role in the immune system than previously thought.

Not getting enough vitamin D has now also been linked to (deep breath) hypertension, heart disease, depression, cancer, MS, macular degeneration, insulin resistance, impaired immunity and back pain. However (and it’s a big however) more studies are needed to provide further evidence and conclusive proof of vitamin D's role here.

Nevertheless, the evidence is such that SACN – the UK body for nutritional policy – recently reviewed the new evidence and in 2016 issued a new recommended intake (RNI) for vitamin D in healthy adults for the very first time. Which is pretty big. We are all now recommended to consume 10 micrograms (ug) per day.

Who’s at risk of deficiency?

Well, if you believe some people, as many as 1 billion of us globally, which would make Vitamin D one of the most common nutrient deficiencies worldwide.

While the numbers may not be quite this high, it’s certainly true that a lot of us are probably getting insufficient amounts. The problem is that diet alone is probably not enough to provide us with what we need, and even oily fish may not always be providing us enough thanks to modern fish farming methods.

Those most at risk include the following groups:

1. Those with an increased need for vitamin D (e.g. breastfeeding and pregnant women, growing infants and adolescents, and the obese)

2. Those with reduced sun exposure (e.g. countries with a northern latitude or with seasonal weather e.g. the UK, those with darker skin i.e. Asian and African people, those who wear concealing clothes, the disabled/immobile, and anyone excessively using sun block)

3. Those with a limited diet (e.g. vegetarians and vegans, the lactose intolerant, prolonged breast feeding, those with malabsorption problems i.e. liver or renal disease, and anyone taking certain drugs such as anti-TB drugs or anti-convulsant medicine).

So should I take a supplement?

While vitamin D probably isn’t the miracle nutrient a lot of magazine articles want you to believe, it is essential, and one that many of us are not getting enough of. Boosting your oily fish intake will help (see my recipe for sardine and apple salad for example). So too will spending more time outside during the spring and summer months - see ‘The Vitamins’ page for more info on how much time to spend in the sun and what to eat. But both are unlikely to provide you with enough, particularly during the winter months (you'd have to eat a hell of a lot of fish to hit the 10 mcg/day recommended in the UK! So yes. Vitamin D is one of the few examples of a vitamin where the majority (as opposed to the minority of us) should be taking a supplement.

Sources

https://www.gov.uk/government/publications/sacn-vitamin-d-and-health-report

http://jn.nutrition.org/content/133/4/61e.full.pdf

https://www.youtube.com/watch?v=Cq1t9WqOD-0&t=120s