One could be forgiven for thinking, after reading certain recent media reports, that vitamin D can perform miracles. This humble supplement, it was claimed, had the power to prevent no less an evil than multiple sclerosis, prompting reports of a rush on health food shops and pharmacies.
MS is a chronic illness that affects the nervous system. An afflicted person can have a variety of symptoms, some minor, others with serious consequences for mobility and health. There are few treatments, and there is little agreement about cause.
One theory is that MS is an autoimmune disease, in which the body reacts aggressively to its own cells. Others think it’s a genetic disorder, since the relatives of MS sufferers are at increased risk. Another possibility is that there is an infectious agent responsible, perhaps a viral trigger. One compelling explanation relates to geography: the further one goes from the equator, the greater the number of MS cases, suggesting that a lack of exposure to sunlight could be an influencing factor.
Sunlight exposure is necessary to generate vitamin D from skin. The vitamin is also present in food – fish especially – but not in high enough quantities to meet the body’s demand. There is already evidence showing that people with MS are more likely to have low vitamin D levels. The latest research, published in the online journal Public Library of Science Genetics, combines a number of theories about MS, all of which have some supporting evidence. The researchers found that a known gene, more common in people with MS, interacted with vitamin D. According to their hypothesis, this could then affect the production of white cells, which in turn could mean that the body is unable to recognise “self” cells and attack them – an “autoimmune” response.
So can we be sure that vitamin D will prevent MS? No. It may do, but focused trials will be necessary first. It is important to answer the key questions – does it work? At what dose? For how long? – as soon as possible. And as with any healthcare intervention, there will be complications. We may recall the advice from the Department of Health urging us to stay out of the sun, lest we develop skin cancer. But sun exposure is one way to generate vitamin D. Could this advice to avoid the sun, together with the addition of high-factor sunscreens, actually be doing us harm? The research has yet to be done.
Margaret McCartney is a GP in Glasgow.
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