Well-known as the scourge of scurvy, vitamin C has been considered down the years as a panacea for several ills, from the common cold to complications from diabetes.

But the enticing claim that it can help to fight cancer resurfaced this week, as a study found that high doses of the vitamin could reduce the growth of aggressive tumours in mice by 50 per cent.

Vitamin C, also known as ascorbic acid, is thought of as an antioxidant, protecting cells from the potentially damaging effects of free radicals. On this basis, one in three Britons now takes vitamin supplements - to the bewilderment of many dietitians, who say that the body's nutritional needs can be amply obtained by eating a balanced diet.

But the recommended daily amount of vitamin C varies widely. In the 1970s, the Nobel prize-winning chemist Linus Pauling encouraged people to take 1,000mg of vitamin C daily to ward off illness. This dose is unlikely to cause any harm, the Food Standards Agency says. But its own recommendation is that just 40mg a day is enough - a small orange, a large peach or a single kiwi fruit provides this much. Other good sources are peppers, blackcurrants, strawberries and potatoes.

A review of scientific evidence by the respected Cochrane Collaboration concluded in April that there was “no convincing evidence” that antioxidant supplements help to keep diseases such as cancer at bay, and added that the unnaturally large doses of vitamins and minerals they contain may actually do more harm than good.

Some patients - especially those with aggressive cancers who lack any other effective treatment - already take hefty amounts of antioxidants such as vitamin C in the belief that they will complement existing therapies. But despite some positive outcomes noted by researchers such as Professor Pauling, reliable evidence that vitamin C therapy works has been lacking. All the randomised controlled trials seem to suggest that it doesn't.

However, the latest study, published in the Proceedings of the National Academy of Sciences, involved injecting ascorbic acid directly into the bloodstream of mice rather than have them swallow it, avoiding the problem that both mice and men do not normally absorb significant amounts of vitamin C to be effective against cancer.

The daily dose supplied to the mice by the team from the National Institutes of Health (NIH) in Bethesda, Maryland, was equivalent to 4,000mg per kilogram of body weight daily (meaning that, in principle, nearly 300g would be needed for the average man).

At such high doses, the researchers found that chemical reactions sparked by the vitamin soon led to the formation of hydrogen peroxide - the common disinfectant and hair bleach - in the liquid-filled spaces between cancer cells. This destroyed even aggressive, hard-to-treat tumours while leaving healthy tissue intact.

Tackling cancer with vitamin C would have the bonus of being relatively cheap, and the scientists from the NIH study reported on two early clinical trials at the University of Kansas which showed that therapeutic doses similar to those seen in mice could be achieved in humans.

But further trials involving human patients are clearly needed before any thought can be given to injecting vitamin C as a viable treatment for cancer.

Separate research even suggests that high doses of antioxidants can reduce the effectiveness of radiotherapy and chemotherapy, our strongest weapons against the disease, so it may eventually be helpful for only a minority of hard-to-treat cases.

The key message for all of us remains: keep eating vitamin C as part of your five-a-day. But don't expect a quick fix from a vitamin pill.

David Rose is a health correspondent of The Times. He recently won the Medical Journalists' Association's health journalist of the year award.

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