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Vitamin D –


09 May 2012

Vitamin D is a vitamin and pro hormone which is synthesised by the body when our skin is exposed to Ultraviolet light. It is estimated that 70 per cent of Brits suffer from vitamin D deficiency during the spring and winter months – a worrying statistic given the vital role this vitamin plays in maintaining our everyday health and wellbeing.

Our knowledge of vitamin D is changing. In the 1970s this hormone was found to control absorption of calcium in the intestine and the deposition of calcium in the bone. But now we understand much more. Recent medical research tells us that receptors for the vitamin D hormone are found in more than 38 different tissues or organs in the body, not just bone and the gut, as was originally believed. These findings have snowballed, with numerous research studies discovering even more compelling evidence to suggest that lack of vitamin D is linked to many different diseases, including arthritis, some cancers, fibromyalgia, multiple sclerosis and rickets. Further studies have found moderate evidence of links with other diseases, for example asthma, the common cold, depression, Parkinson’s disease and stroke.

Vitamin D deficiency has been brought into the health and media spotlight really quite suddenly over the last decade as relatively recent research has shown the extent of the impact deficiency has on our major health issues. Early studies from a century ago show the importance of vitamin D supplementation for prevention of the bone disease Rickets. Experts argued early on that this disease could be cured not only by an ‘accessory factor’ in food, but also by the action of UV light through the skin. It was after this that more was understood about how vitamin D is produced in the body.

Sunlight and vitamin D

Ultraviolet B rays from the sun convert a universally present form of cholesterol found in epidermis, which is the outermost layer of the skin, into an inactive form of vitamin D. This is then carried to the liver, where it picks up extra oxygen and hydrogen molecules. However it cannot function until the vitamin travels to the kidneys and acquires a final pair of oxygen and hydrogen molecules to become the final, active form of vitamin D.

In evolutionary terms, as we migrated from our sunny equatorial homelands to more northerly locations, we evolved with lighter skin pigmentation to absorb the weakening UVB rays. But in the last hundred years or so humans have been retreating increasingly away from the sun and many simply don’t achieve the level UVB absorption they need to maintain even basic health.

Firstly, the somewhat unfortunate geographical location of the UK is often overlooked. When the sun is below 45 degrees in the sky, nearly all of the UVB it produces is absorbed by the atmosphere, rather than our bodies. So in the UK, the angle of our winter sun is simply not strong enough to ensure sufficient vitamin D production at the levels we need. Even when the strength and angle of the sun is good enough for optimum vitamin D generation in our bodies, our nation’s infamous cloudy weather often blocks it out completely, hindering the absorption of those all important UVB rays. Therefore only a very few people – those who lead outdoor lives most of the year round – are likely to generate enough vitamin D.

Another barrier to sun exposure is today’s busy, modern life, which tends to go hand-inhand with working longer hours and spending more time indoors. For many people nowadays it’s habitual to get up, walk to the car, spend the day in the office, eat lunch at a desk, then go home. Exposure to the sun is playing a decreasing role in our daily lives. Children are at risk for different reasons. Whereas kicking a ball round a field was still the pursuit of choice for many a youngster only 10 or 20 years ago, now children find entertainment from the latest games console, computer terminal or social media site – all behind closed doors, all hidden away from sunlight.

There are also genuine concerns – but not without a fair dose of scaremongering – with regards to sun exposure and skin cancers. This has resulted in the regular overuse of high factor sunscreens, particularly on children, producing yet another shield to the healthy, natural absorption of vitamin D.

At-risk groups

From what has been reported in the last decade, it is safe to say that this lack of sun exposure is affecting the health of the population – particularly in the UK. There are now several at-risk groups which have been identified as being especially vulnerable to suffering from vitamin D deficiency, including people over 50, the housebound, vegetarians, those who regularly cover up in the sun and people with darker skin.

But it is two very specific groups – pregnant and nursing women and children under five, who are causing growing concerns to nationally significant health officials – notably the Chief Medical Officer for England. In January, Professor Dame Sally Davies asked health professionals to recommend vitamin D supplementation to these at risk groups after cases of rickets began to make headlines again.

Importantly, new research now shows that pregnant women with low levels of Vitamin D may have higher rates of pregnancy related health conditions, including pre-eclampsia, gestational diabetes, birth by caesarean section and a lowering of the immune system. In addition, babies are born with 50 to 60 per cent of the mother’s vitamin D levels, putting them at even greater risk of future health problems if their mothers are already deficient. Unfortunately, many mothers are often not informed of these risks during pregnancy, occasionally with tragic consequences. Vitamin D deficiency has been discovered in a significant number of children who died of sudden infant death syndrome, whilst two senior paediatric pathologists have reported further infant deaths and injuries which could be put down to vitamin D deficiency and linked bone diseases.

With this in mind, there is clearly the need for a more sensible approach to sun exposure and a greater understanding of the need to supplement. Some confusion remains as to how much an individual should supplement. The problem lies in trying to provide a single guideline for different people, often living in very different environments and leading subtly different lifestyles. But one thing’s for sure – when it’s clear an individual is not able to spend the required time exposed to sunlight, or during the six months of the year when the sun’s UVB rays are simply not strong enough to stimulate vitamin D production in our bodies, we must look to daily supplementation.

Supplementation

There are different ways of supplementing our vitamin D levels. Food fortification is one way, but is not enforced in the UK, unlike many countries. Some UK children’s cereals are now fortified with low levels of vitamin D. But for most people living in the UK, taking a supplement is likely to be the most readily available way of reaching optimum levels.

Vitamin D supplementation is not an exact science as it depends upon skin type and everyday natural sun exposure. Although vitamin D is a fat soluble vitamin, taking too much vitamin D in the UK is virtually impossible. As a rule of thumb, I personally recommend 1,000iu per 25kg of body weight as a maintenance dose – see figure 1. But of course those with deficiency will need a higher dose to begin with in order to raise blood levels to a level that can be maintained.

Tablet forms of vitamin D are generally the most accepted way of supplementing and there are numerous brands on the market, offering varying doses for different needs. This form of supplementation can work effectively, but stressful lives, coupled with an ageing population, mean our digestive efficiency is worsening. Our body is therefore less likely to absorb nutrients from this traditional form of oral supplementation.

With this in mind, there are some valuable alternatives. The sublingual route delivers the vitamin under the tongue, via the mucous membrane, which is then transported directly into the bloodstream, rather than through the small intestine. Sublingual supplements can come in the form of drops, dissolving tablets or sprays, which mean the formulation is already broken down for easier absorption. This is ideal for vitamin D supplementation, which relies on the bloodstream to transport the vitamin direct to the liver and kidneys, where it can be absorbed. So the faster it can enter the bloodstream, the sooner the body can benefit from it, making sublingual sprays one of best methods for fast absorption when the body really needs it.

Andrew Thomas, managing director of BetterYou


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