Over the years, vitamin C has established itself as the pre-eminent nutrient for combating the common cold. Some individuals regularly take supplements of this vitamin in the belief that this will reduce their risk of succumbing to the sniffles or something more serious. Others will load up on vitamin C once an infection has taken hold in an effort to contain symptoms and speed recovery. However, the hopes of those who put faith in vitamin C as an anti-infective agent seemed to be dashed recently on the publication of study which appeared to show that this nutrient is a relatively ineffective weapon in the cold war.

The research in question, published in the journal Public Library of Science (PLoS) Medicine, analysed data from several studies and concluded that taking vitamin C at a dose of 200 mg or more each day did not reduce the risk of succumbing to the common cold. However, not all of the results from this review of the evidence were as disappointing: it was found, for instance, that in individuals subjected to cold weather or considerable physical stress (such as marathon running), vitamin C supplementation cut the risk of cold infection by half.

Also, while taking vitamin C prophylactically did not seem to reduce the risk of catching a cold for most people, it did lead to a statistically significant reduction in the duration of an ensuing infection in both children and adults. The authors of the study commented that the consistency of the findings across studies suggested that vitamin C has a genuine biological effect. This concept is supported by a wealth of evidence which reveals vitamin C to have the ability to stimulate and support the immune system through a variety of mechanisms.

The PLoS Medicine study found that supplementing with vitamin C once an infection had set in did not seem to confer benefit. However, studies of this nature have generally used pretty modest vitamin C dosages. My experience in practice, supported by at least some scientific evidence, is that once a cold has got a hold, only large doses of vitamin C stand a decent chance of speeding recovery.

I generally recommend that individuals who feel they are going down with something should start by taking 3 grams of vitamin C right away, followed by 1 g of vitamin C every waking hour until symptoms disappear. One study using high doses of vitamin C saw an 85 per cent reduction in cold and flu symptoms compared to an untreated group. Such large doses of vitamin C may loosen the bowels, though this symptom invariably resolves once the dosage is sufficiently reduced. The evidence suggests that the amount of vitamin C found in foods such as citrus fruits, kiwi fruits and strawberries is unlikely to do much to keep colds at bay, although it should be borne in mind that the eating of such foods is likely to benefit the body in lots of other ways. It seems that high dose supplementation of vitamin C is required if this nutrient is to offer effective cold comfort.

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