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.

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