Do we need vitamin D supplements?

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Health / Medicine / Myths

There’s a lot of hype around vitamin D. We’ve long known it’s essential for healthy bones, but over the last decade it’s been claimed low vitamin D levels are linked to a whole host of other illnesses. How clear are those links and how many of us really need vitamin D supplements?

So many supplements to choose from. Image credit Angel Sinigersky via Unsplash

Get some rays

Also known as the sunshine vitamin, there are two ways to get vitamin D. The first is the same way we get all the other vitamins and minerals essential to good health: from the food we eat. Foods high in vitamin D are oily fish and egg yolks. Because many people’s diets are low in vitamin D, in some countries, foods like milk, orange juice and cereal have vitamin D added during processing.

But there’s another way to get vitamin D – your body can make it through a series of steps starting with your skin being exposed to the sun. How easy it is for your body to make enough vitamin D depends on how dark your skin is, and where you live. For example, in Australia in summer, just a few minutes each day of sun exposure in the mid-morning or mid-afternoon is enough for most people.

Why we need vitamin D

We’ve known for a long time that vitamin D is essential for healthy bones. This is because vitamin D plays a vital role in absorbing calcium from your gut. Without enough vitamin D, children develop rickets – weak and soft bones, and in the worst cases, bone deformities. A lack of vitamin D is also associated with osteoporosis and other bone conditions in adults.

The importance of vitamin D in contributing to the growth of healthy bones is not in any dispute. But over the past decade, it’s been claimed low vitamin D levels are also responsible for a variety of other illnesses. Studies have reported links between low vitamin D levels and cancer, heart disease, autism, depression, type 1 diabetes, high blood pressure and rheumatoid arthritis among other conditions.

Popping pills

These research claims led to a massive media focus on vitamin D. For example, in 2010, the New York Times declared ‘a huge part of the population….are deficient in this essential nutrient’. The US-based Vitamin D Council helped to spread the message that we would all be healthier with higher levels of vitamin D became widely accepted. Dr. Oz claimed vitamin D was ‘the number 1 thing you need more of’.

It’s an appealing story: we evolved near the equator where there is plenty of intense sun year-round. Humans also used to spend almost all their time outside wearing minimal clothes. It makes sense that people working in offices, particularly those living far from the equator could become vitamin D deficient.

With all the media hype about vitamin D as a cure-all, it’s no surprise people turned to vitamin D supplements. Pills are a quick fix – much easier than eating sardines or herring every day. Today, millions of people take vitamin D tablets without any evidence it is doing them any good. We know people in the US spend more than a billion dollars a year on vitamin D supplements.

At the same time, millions of people who have no medical complaints or symptoms, and no particular disease risks, are having their vitamin D levels tested. But there’s little consensus about the best form of vitamin D to measure in the body,  and how to best measure it. Not only that, but there is no general agreement on what level of vitamin D actually constitutes a deficiency.

One osteoporosis researcher has gone on the record claiming vitamin D has become ‘a religion’.

The truth about vitamin D

Recent large-scale studies have upended the idea that a lack of vitamin D is the cause of most of the illnesses it has been linked to. A recent study showed vitamin D supplements don’t prevent heart attacks. Another showed vitamin D supplements didn’t reduce the risk of cancer in older women.

Late last year a large clinical trial involving 25,000 people found no evidence for the benefits of the supplements in protecting against heart disease or cancer. Another large study of 5,000 New Zealanders found no evidence vitamin D supplements prevented heart problems.

Interestingly, a review of 81 existing studies also found no evidence that vitamin D supplements reduced falls or bone fractures. The results of many of the other studies claiming links between low vitamin D and illnesses have been called into question after further review.

On the other hand, there does appear to be evidence that people who live in areas with high sun exposure, and particularly those who spent lots of time in the sun as kids are less likely to develop multiple sclerosis. Recent studies have also supported a possible association between vitamin D levels and depression.

Some researchers are concerned people have assumed that if some vitamin D is good, more must be better. As a result, people are buying high-dose vitamin D tablets online. But unlike the B and C vitamins, vitamin D can be stored in the body and an overdose can cause vomiting, nausea, loss of appetite and weakness.

Please always follow your doctor’s advice. But if you’ve decided to take vitamin D supplements on the basis of what you’ve read in the media or heard on the grapevine, it might be time for a rethink. You may be wiser to save the money and spend it on more real food instead.

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