Too much of a good thing

Excessive quantities of vitamin C can be detrimental to health

Large doses of vitamin C may do more harm than good and could even help trigger serious diseases such as cancer and rheumatoid arthritis, according to new research.

Although the recommended daily dose of vitamin C is 60mg, doses of up to 1,000mg are sold in shops.

The vitamin which helps the body to fight infection is also a powerful antioxidant preventing the conversion of nitrates from substances such as tobacco smoke, smog and some vegetables into cancer-causing substances.

However, new research shows that doses of 500mg can actually promote the damage it is meant to reduce.

The discovery follows resarch led by Ian Podmore at Leicester University which looked for evidence of DNA damage caused by oxygen in white blood cells.

Volunteers spent six weeks taking a daily dose of 500mg of vitamin C followed by six weeks without.

After a series of tests, scientists found that while the vitamin did have some beneficial effects, DNA damage was significantly increased.

No substitute for a balanced diet

Nutrition expert Wynnie Chan, from the British Nutrition Foundation, said the findings demonstrated the necessity of a balanced diet.

"It is true that people take high doses of vitamin C not only for its antioxidant properties but also because they think it helps prevent colds," she said.

"We do caution people not to take excessive doses of vitamins and minerals because of their toxic effects.

"People should really try to get their nutrients from a varied and balanced diet and not rely on the magic effect of supplements."