The idea that vitamin C supplements fight off colds is a myth, researchers have concluded.
A review of data from 30 studies involving more than 11,000 people found no evidence that, for the average person, taking extra vitamin C can stop sneezes, sniffles and coughs.
Only individuals under extreme physical stress, such as marathon runners, skiers and soldiers, stood to benefit, said the Australian and Finnish scientists.
They were 50 per cent less likely to catch a cold if they took daily vitamin C, research found.
Generally, the protection offered by the vitamin supplements was so slight it was not worth the effort or expense, said the researchers.
Professor Harri Hemila, from the Department of Public Health at the University of Helsinki, said: ‘It doesn’t make sense to take vitamin C 365 days a year to lessen the chance of catching a cold.’
The new analysis appears in the latest issue of The Cochrane Library, published by the Cochrane Collaboration, an international organisation that evaluates medical research.
Scientists pooled together information from studies spanning several decades, which looked at the effect of taking daily supplements of at least 200 milligrams of vitamin C.
This kind of ‘meta-analysis’ is often more sensitive than a stand-alone study and better able to spot subtle trends.
Controversy has surrounded the protective effects of vitamin C since its discovery in the 1930s.
The belief that vitamin C can cure the common cold took hold in the 1970s, largely thanks to the US Nobel Prize-winning chemist Dr Linus Pauling, who championed the vitamin.
His book, Vitamin C and the Common Cold, encouraged people to take large vitamin C doses of 1,000 milligrams daily.
The current recommended daily allowance of vitamin C is 60 milligrams. Just one 220-millilitre glass of orange juice contains more than that – about 97 milligrams.
The Cochrane researchers acknowledge that vitamin C supplements, taken alone or with other substances, might have health benefits other than keeping adult colds at bay.
Prof Hemila said he wanted to see more studies on colds in children, and the effect of the vitamin on pneumonia.
‘Pauling was overly optimistic, but he wasn’t completely wrong,’ he added.
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