Doubt raised again over value of antioxidant supplements

According to a new study by French researchers, antioxidant supplements do not protect women against skin cancer and in fact they may possibly increase their risk.

Dr. Serge Hercberg, a professor of nutrition at the Medical University of Paris and along with a team of researchers examined the effects of antioxidant doses on skin cancer as part of a larger study which was considering the effects of antioxidants on cancer and ischemic heart disease.

The authors say excessive exposure to sunlight or other sources of UV light can overwhelm the skin's antioxidant power and for this reason antioxidant pills have been recommended for the prevention of sunburns and for their protective properties.

Antioxidants are thought to reduce disease risk by cutting down on the unhealthy effects of "free radical" molecules that damage cells.

The new findings raise concerns over the long-term use of supplements such as beta-carotene used most notably by sun lovers and people wanting to look tanned.

For the study 13,000 French adults, ages 35 to 60, were divided into two groups; half took an oral daily capsule of antioxidant that contained vitamins C, E, beta carotene and selenium while the other half took a placebo.

Hercberg says the doses were below the level of many pills on the market.

The participants were tracked for a period of 7.5 years and in that time, 157 cases of skin cancers were reported, including 25 melanomas, the most deadly form.

The research team found in the women, the incidence of all types of skin cancer combined was actually higher in the antioxidant group, and so was their incidence of melanoma.

The incidence of non-melanoma skin cancers, when evaluated separately, did not differ between the antioxidant and placebo groups in men or women.

In the men, there was no difference in any form of skin cancer (including melanoma) between the two groups.

In the antioxidant group, 51 women developed skin cancer, while 30 in the placebo group did; among the men, 43 in the placebo group and 33 in the antioxidant group got skin cancers.

For melanoma, the incidence did not differ significantly between the men's treatment group, 6 in the placebo group and 3 in the antioxidant group got it.

But 3 women on placebo and 13 on antioxidants got melanoma which represents a significant difference, say the researchers of four times greater for women taking the antioxidant supplements.

Hercberg says other antioxidant studies have produced a mixed bag of results with some suggesting a higher risk of lung cancer in heavy smokers who regularly took high doses of beta-carotene.

However previous research on animals found that when antioxidants are given prior to exposure to ultraviolet light a protective effect against skin cancer was provided.

Other research implies on the one hand that antioxidant supplements might protect against prostate cancer incidence in men with low blood levels of prostate specific antigen (PSA) but on the other, research also suggests that the nutrients might increase prostate cancer risk in men with a high PSA.

PSA levels are a marker for pre-existing prostate cancer risk.

Hercberg speculates that this is what happened in the women who developed more skin cancers after taking antioxidants.

He suggests that if their skin cancer was already developing, taking an antioxidant might not have helped.

Experts say further research is needed to confirm this as the study has limitations and they advise people to continue to use sunscreens in the sun as they remain the most powerful weapon against skin cancers.

The study comes hot on the heels of another which found that antioxidants do not prevent heart disease in high-risk women.

The study is published in the September issue of The Journal of Nutrition.


The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of News Medical.
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