Should we all be taking a ‘sunshine’ supplement?
Vitamin D has been hailed as a cure-all but does popping it as a pill do any good – and can you take too much, asks Rosa Silverman
It goes by a variety of flattering names: the “sunshine” vitamin; the superstar supplement; the cure-all. And if recent research is to be believed, vitamin D really does live up to its billing – good news for anyone feel devoid of verve and vim as we slowly limber up to the shortest day of the year. But it’s not simply good to boost energy levels. In the last few years we have been told that vitamin D supplements can also protect against severe asthma attacks; help burns to heal and prevent scarring; prevent millions of colds; improve function in damaged hearts; help prevent rheumatoid arthritis; and could even ward off dementia.
The vitamin, which helps regulate the amount of calcium and phosphate in the body, is important for bone health and immune system function, and a lack of it can cause rickets. If that’s not enough to send you rushing to the pharmacy to stock up on tubs of the stuff, then maybe the fact that our natural levels of vitamin D tend to plunge during these cold winter months will be.
Last year, Public Health England took the unprecedented step of advising the whole population to increase their vitamin D intake during autumn and winter, warning that the combination of modern lifestyles and our gloomy weather had led to widespread deficiencies. Our bodies make most of our vitamin D from direct sunlight on the skin, but poor diets as well as indoor jobs and general lack of sun have been blamed for reducing our levels.
Yet the science can sometimes be confusing. On the one hand, we are told that even eating the right foods won’t suffice: “You can’t get the right amount of vitamin D your body needs from food,” states the Vitamin D Council’s website. On the other hand, we are told of all the things that can boost our intake: from beef liver and mackerel to egg yolk and shiitake mushrooms, the list of foods rich in D is long enough to include something for everyone (though vegans might struggle more than the rest of us.)
The current NHS advice says: “During the autumn and winter, you need to get vitamin D from your diet because the sun isn’t strong enough for the body to make vitamin D. But since it’s difficult for people to get enough vitamin D from food alone, everyone (including pregnant and breastfeeding women) should consider taking a daily supplement containing 10mcg of vitamin D during the autumn and winter.”
Certainly there’s a weight of medical opinion in favour of this approach. Martin Hewison, Professor of Molecular Endocrinology at Birmingham University’s Institute of Metabolism & Systems Research, says he has been persuaded of the case for vitamin D supplements by both his own work and other people’s studies. A recent study he led suggested maintaining sufficient levels of vitamin D could even help prevent the onset of rheumatoid arthritis.
“There was a time when we were outdoors more and people worked on the land so had more vitamin D inside them than they do now,” he explains. “[Now] most people in the UK are vitamin D deficient and I’m persuaded there’s enough circumstantial evidence [in favour of taking a supplement].”
Some are calling for further action still, arguing that the problem is so severe that vitamin D should be added to food in the UK to combat the population-wide deficiency. In the US, milk has long been fortified with the vitamin. The intervention is credited with helping eradicate rickets in the country, though vitamin D deficiency is still said to be widespread there.
Dr David Llewellyn, who conducted the first population-based studies to identify the associations between vitamin D deficiency and cognitive impairment in the Health Survey for England, pinpoints not only lifestyle factors but also ageing and skin cancer warnings as responsible for our inadequate vitamin D levels.
“We become less effective at producing it through our skin as we grow older,” he says. “Because of advice about skin cancer we have
minimised sunlight exposure. Sensible exposure is essential but that message has been lost.”
Since exposure to sunlight is less of an option in winter, he believes that supplementation during the colder months is advisable. But given that not everyone will heed the message, “there remains a case for fortification”.
Prof Hewison adds: “Fortification of foods has worked quite well in the US. There increasingly seems to be a case [in Britain] for at least discussing this in a more positive manner and providing funding to address how this might work in a large-scale setting.”
Not everyone is equally sold on the idea of vitamin D as a panacea, however. Tim Spector, Professor of Genetic Epidemiology at King’s College London and author of The
Diet Myth, believes the evidence does not support the case for putting a whole population on vitamin D supplements. “You might stop a few hundred people from getting extreme rickets or osteomalacia [a softening of the bones most often caused by severe vitamin D deficiency]. But recent evidence suggests it doesn’t work for other people and doesn’t show any effect for people suffering fractures,” he says.
The NHS guidelines, moreover, are based on an “arbitrary” idea of what level of vitamin D we need, he argues: “Thirty years ago we didn’t call anyone vitamin D deficient. Now half the population is, and it’s because we’ve moved the goalposts.”
The advice is also based on old data, he suggests, “because it takes so long to get a consensus.” Prof Spector, who runs an osteoporosis clinic, was once a “big fan” of the supplements but has changed his mind about them and now routinely asks patients what they eat before giving out vitamin D.
So why have so many people united behind the case for the “wonder vitamin”? In his view, it comes down to an alliance between industry and government that serves the interests of both. “It sells lots for the companies, and governments love it because they’re seen to be doing something, so it’s a bandwagon everyone gets on.”
The danger, he warns, is that popping a vitamin supplement can offer a false sense of security. “People think if they take vitamins they don’t have to worry about what they eat or their lifestyle. We should be going in the sun during summer and eating vegetables and oily fish. I’m not saying no one should take vitamin D supplements, but they shouldn’t be given out like Smarties.”
Meanwhile, although the vitamin D pills available in pharmacies are widely deemed to be safe, the claims made for the vitamin’s healing qualities have prompted some to risk their health by buying dangerously high doses online. Earlier this year, Britain’s leading NHS testing laboratory warned that hundreds of people were taking toxic levels of vitamin D in supplements containing up to 2,250 times the recommended dose. This puts them at risk of heart and kidney problems, said the City Assays lab in Birmingham that identified the problem.
Prof Hewison is among those who take doses far higher than recommended, buying an unregulated product online during the winter months. “The current recommendation is 400 units and I take 2,000 a day,” he says. “It’s unregulated so it could be 20,000, it could be 200. There have been a handful of people getting toxicity but it’s very rare to see this.
“If you look at many clinical trials, 400 units per day is the placebo arm of the vitamin trial, yet that’s the amount the Government says we should be taking. This is where the vitamin D field gets rather confusing because we don’t really know what is the best level to have.”
Dr Llewellyn agrees the optimal dose remains somewhat uncertain. But, he says: “Sensible exposure to sun during summer and supplementation during winter seems a good compromise.”