Your report (24 December) on the proposal that there should be artificial supplementation of Scotland's food by vitamin D to reduce the frequency of multiple sclerosis did not address the two main questions of whole-population interventions. Is it effective? Is it safe?
Current evidence strongly supports a role for low levels of vitamin D in the development of MS, as your article says. However, other factors are also involved. There are no population-based clinical trials supporting the effectiveness of artificial dietary supplementation by vitamin D in lowering the frequency of MS.
On the matter of safety, vitamin D supplementation should have no adverse effect on healthy individuals. However, whole-population medication also affects the frail, elderly and ill. There are a number of illnesses in which vitamin D supplementation is potentially harmful. These are diseases associated with elevated blood calcium and include hyperparathyroidism, myeloma, lymphoma, tuberculosis and sarcoidosis.
How common are these conditions? In Scotland hyperparathyroidism alone affects 6 per 1,000 of the population – it is several times more frequent than MS. So while we need to examine this issue carefully, mass medication with no published evidence of benefit, and with the risk that more people could be harmed than are likely to benefit, would be irresponsible.
Professor Stewart Fleming
University of Dundee
Your article highlights major problems in medical research. As the Scottish chief medical officer said, the issue can only be settled by a large, simple "randomised clinical trial". However, Scotland alone could not afford the required size of a trial to prevent MS with vitamin D. Collaboration is needed with the rest of Britain, but the current funding mechanisms do not allow for such a large trial, of probably 20,000-30,000 people followed for five years, without special high-level arrangements.
The funders include the research councils and the Department of Health under its disparate, rather dysfunctional Health Technology Assessment (HTA) and Medicines and Healthcare Products Regulatory Agency. The HTA has received many vitamin D and other trial proposals, generally turned down at their first hurdle by statisticians with inadequate experience of clinical and public health issues.
A huge bureaucracy suffocates originality and prolongs applications; even after approval for ethics, implementation is obstructed again by local "research and development" processes that may take months to surmount. In our institution alone, there are over 30 people employed by the NHS to monitor the minutiae of trials, and many more people in primary care now being paid to recheck what ethics committees have already agreed. That cost of policing imaginary risk is enormous, and delays patient benefit.
Professor JK Cruickshank
King's College London