LONDON (Reuters) - A leading British cancer charity called on Friday for health warnings on vitamin supplements containing beta-carotene, saying they can increase a smoker's risk of developing lung cancer.

The Cancer Research Campaign cited two studies that showed the danger of the supplement for smokers.

``My advice to smokers, who can't kick the habit, is don't add to your risk of getting cancer by taking beta-carotene supplements,'' Professor Gordon McVie, the director general of the charity, said in a statement.

``The research is cast-iron in my view and I feel certain most smokers are not aware of the risk.''

Tomatoes, carrots and other yellow fruits and vegetables are rich in beta-carotene.

The body converts it into vitamin A, which is important for healthy growth, good vision and energy levels. It is also an anti-oxidant and neutralises the effects of free radicals which damage DNA in the body and can lead to cancer.

But McVie said there seems to be a difference between naturally occurring beta-carotene and pills containing it, although medical experts are not sure what it is.

A study of 29,000 smokers in Finland, which was published in the New England Journal of Medicine, showed that smokers were 18% more likely to get lung cancer if they were given beta-carotene.

Research in the United States also found that the supplement raised the risk of lung cancer in asbestos workers and smokers.

Britain's government recommended in 1998 that beta-carotene supplements should not be used to protect against lung cancer, but McVie said the warning had been ignored.

The government has also asked a group of experts to assess the safety of the supplements. It is due to report its findings later this year.

``Eating vitamins in everyday foodstuffs, as part of a balanced diet, is proven to be good for you,'' McVie said.

``But vitamins are very active and very effective substances and should be treated as a medicine when they are given in pill form.''

Solgar, a leading manufacturer of health products, said the negative effects shown in the two studies could be due to the use of a synthetic source of the supplement.

McVie said it was up to manufacturers to prove whether people would react differently to supplements of beta-carotene from natural sources.

Britons spend about 80 million pounds ($120 million) on vitamin supplements each year. ($1-0.6661 Pound)

　　(From Yahoo)