Meta-study: supplements containing vitamin D protect against colds
A supplement containing extra vitamin D protects against colds. Adrian Martineau, a researcher at Queen Mary University of London, is sure of it from the meta-study he published in the BMJ.
Martineau and his colleagues put together data from 25 previously published trials in which a total of 11,321 people had participated - and reanalysed them.
On average, vitamin D supplementation reduced the chance of developing a cold by 12 percent.
That percentage rose to 19 percent when the participants took vitamin D daily or weekly. Taking a very high dose every few weeks worked less well, the researchers discovered. Occasional very high doses lowered the likelihood of developing a cold by a few percent.
In populations where the average vitamin D level was lower than 25 nanomoles/litre supplementation worked, not surprisingly, best. When the participants in these groups were given vitamin D daily or weekly then their chances of catching a cold decreased by up to seventy percent.
No side effects were observed, although the researchers suspect that trials published until now have not been completely honest on this point. They were able to show statistically that a few studies in which people did develop side effects probably accidentally disappeared into a desk drawer.
"Our study reports a major new indication for vitamin D supplementation: the prevention of acute respiratory tract infection," the researchers wrote. "We also show that people who are very deficient in vitamin D and those receiving daily or weekly supplementation without additional bolus doses experienced particular benefit."
"Our results add to the body of evidence supporting the introduction of public health measures such as food fortification to improve vitamin D status, particularly in settings where profound vitamin D deficiency is common."
Mark Bolland and Alison Avenell wrote in a BMJ comment that in their opinion the government should wait with introducing food fortification programmes. "The results are heterogeneous and not sufficiently applicable to the general population. We think that they should be viewed as hypothesis generating only, requiring confirmation in well designed adequately powered randomised controlled trials." [BMJ 2017;356:j456.]
Supplement containing vitamin D halves chance of flu 24.09.2016
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