Vitamins 'should carry health warning'
Health warnings for smokers should be carried on bottles of vitamin supplements containing beta-carotene, says the Cancer Research Campaign.
The charity's Director General Professor Gordon McVie said the warning is necessary because there is evidence that supplements of beta-carotene, which can be converted into Vitamin A, can raise smokers' risk of developing lung cancer.
Vitamins are very active and very effective substances and should be treated as a medicine
Prof Gordon McVie
Cancer Research Campaign
Professor McVie advised people to treat all vitamin supplements with caution because they can be as powerful as medicines.
He said: "Eating vitamins in everyday foodstuffs, as part of a balanced diet, is proven to be good for you.
"But vitamins are very active and very effective substances and should be treated as a medicine when they are given in pill-form."
One in five people in the UK take a vitamin supplement and Â£80 million are spent on them every year in Britain alone.
The possible risk associated with beta-carotene supplements was uncovered by clinical trials originally designed to test how effective the pills were in reducing the risk of lung cancer.
Against all expectations, the opposite turned out to be the case.
A Finnish study of 29,000 male smokers, published in the New England Journal of Medicine, showed that participants were 18% more likely to develop lung cancer if they were given beta-carotene.
Another study in the US discovered that asbestos workers and smokers were 28% more likely to develop lung cancers if they were given beta-carotene supplements.
This study of 18,000 men and women, which was published in the Journal of the National Cancer Institute, was stopped following the negative result.
Professor McVie said: "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.
"The research is cast iron in my view and I feel certain most smokers are not aware of this risk."
The Government recommended in 1998 that beta-carotene supplements should not be used to protect against lung cancer.
Professor McVie said this warning has been largely over-looked or ignored.
An expert group on vitamins and minerals is currently assessing the safety of beta-carotene supplements, at the request of the Government, and is expected to report its findings next year.
Beta-carotene occurs naturally in tomatoes, carrots and other yellow foods.
It is important for our health because our bodies can convert it into Vitamin A which helps vision, growth and energy levels.
Doctors think beta-carotene might have a role in preventing cancer because it is an anti-oxidant.
Anti-oxidants neutralise the effects of free radicals which are harmful chemicals released in our bodies.
But there is an apparent difference between the health benefits of beta-carotene in pills and in natural foodstuffs and experts do not know why.
A spokesman for the dietary supplement company, Solgar, said on the programme that although a negative effect had been shown for beta-carotene in trials, it had been a synthetic source of the anti-oxidant.
He argued that this adverse effect might not happen with natural sources of beta-carotene as used in many dietary supplements.