Mechanism isn't clear, and new findings don't apply to men
MONDAY, Aug. 20 (HealthDay News) -- Taking antioxidant supplements won't protect against skin cancer and may actually boost the risk, at least in women, according to a new French study.
"Taking into consideration our results, we are particularly concerned by the use of long-term supplementation, notably in sun-seekers and people wanting to look tanned [using beta-carotene]," said researcher Dr. Serge Hercberg, professor of nutrition at the Medical University of Paris.
The new findings come on the heels of a study, published in mid-August in the Archives of Internal Medicine, that found that antioxidants don't prevent heart disease risk in high-risk women.
In the new French study, published in the September issue of The Journal of Nutrition, Hercberg's team looked at the effects of antioxidant doses on skin cancer. The research was conducted as part of a larger study that looked at the effects of antioxidants on cancer and ischemic heart disease.
Antioxidant nutrients are thought to reduce disease risk by cutting down on the unhealthy effects of "free radical" molecules that damage cells.
The researchers assigned almost 7,900 women and more than 5,100 men to take either an oral daily capsule of antioxidant or a placebo that looked the same. The antioxidants included 120 milligrams of vitamin C, 30 milligrams of vitamin E, 6 milligrams of beta-carotene, 100 milligrams of selenium and 20 milligrams of zinc.
"They are not high doses," Hercberg said. "They are at a level below a lot of pills you can find to buy over the counter."
The men and women were followed for about 7.5 years. In that time, 157 cases of any form of skin cancers were reported, including 25 melanomas, the most deadly form.
The team found that, in women, the incidence of all types of skin cancer combined was actually higher in the antioxidant group, and so was their incidence of melanoma.
But the incidence of non-melanoma skin cancers, when evaluated separately, did not differ between the antioxidant and placebo groups in men or women. In 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.
As 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 -- a significant difference, the researchers said.
Antioxidant studies have yielded mixed results, Hercberg stressed. For example, in previous studies, researchers saw a higher risk of lung cancer in heavy smokers who regularly took high doses of beta-carotene.
Studies have suggested that antioxidant supplements might protect against prostate cancer incidence in men with low blood levels of prostate specific antigen (PSA), Hercberg said. But research has also suggested 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.
That could also be happening in the women who got more skin cancers after taking antioxidants, he theorized. If their skin cancer had already been developing, taking an antioxidant might not help, Hercberg speculated.
While the study is interesting, further research is needed to confirm it, said Dr. Ariel Ostad, a spokesman for the Skin Cancer Foundation and a New York City dermatologist not involved in the study.
He said the study did have one serious limitation. "It does not take into account sunscreen use," he said. If the participants tended not to use sunscreen, that could have affected the results.
Meanwhile, Ostad added, taking care in the sun is important, and "sunscreens are by far the most powerful" weapon to prevent skin cancers.
To learn more about preventing skin cancer with sunscreens, visit the Skin Cancer Foundation.
SOURCES: Serge Hercberg, M.D., Ph.D., professor, nutrition, Medical University of Paris, France, and director, department of nutritional epidemiology, French Institute for Health and Medical Research; Ariel Ostad, M.D., dermatologist and spokesman, Skin Cancer Foundation, New York City; September 2007, Journal of Nutrition