Cold comfort: vitamin C myth exposed

[Marulus]

Cold comfort: vitamin C myth exposed

Ian Sample
Wednesday July 18, 2007
Guardian Unlimited


Daily doses of vitamin C do little to protect people from the common cold, scientists revealed today.

In a survey of scientific studies spanning more than two decades and including more than 11,000 people, those who took 200mg of vitamin C daily had almost as many colds as those who took no supplements. The vitamin also failed to have a substantial effect on the length and severity of a person's cold.

The supposed cold-combating powers of vitamin C have been hailed since its discovery in the 1930s. In his book Vitamin C and the Common Cold, the Nobel laureate Linus Pauling encouraged people to take 1,000mg of the vitamin daily to ward off colds, though the current recommended daily allowance of vitamin C is just 60mg. A large glass of orange juice contains nearly 100mg.

However, the latest survey, compiled results from 30 different studies around the world, concluded that only people who were exposed to exceptionally high levels of stress, such as marathon runners, skiers and soldiers on sub-arctic exercises, had fewer colds as a result of taking the vitamin. Among these, a daily supplement of vitamin C reduced the chances of catching a cold by half.

Harri Hemilä at Helsinki University, who led the survey, said that for most people the cold-preventing effect of taking daily vitamin C supplements was so slight that it was not worth the effort or expense. "It doesn't make sense to take vitamin C 365 days a year to lessen the chance of catching a cold," he said.

The review appears in the latest issue of the Cochrane Library, an international organisation that is widely regarded as the most prestigious medical research evaluating authority.

Despite finding that vitamin C did little to help protect people against common colds, however, Dr Hemilä said more scientific studies were required to investigate whether the vitamin helped to treat colds and pneumonia in children.

Vitamin C was not a panacea, but neither was it useless, he said. "Pauling was overly optimistic, but he wasn't completely wrong."

A separate study recently warned that people who took regular supplements of vitamins A, E and beta-carotene in the hope of living a fitter, longer life were instead at risk of dying younger.

Like vitamin C, the supplements are marketed as antioxidants capable of mopping up free radicals, highly reactive particles produced in the body that are thought to play a role in ageing.
But the study, published by the Journal of the American Medical Association, found that during 47 trials involving more than 180,000 people, those who took the supplements were at greater risk of dying than those who did not.

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