Antioxidants Does Not Reduce Gastric Cancer Risk

30/01/07 Taking antioxidants, compounds such as vitamins A and C and beta-carotene that protect cells from damage in tissue culture, does not reduce the risk of gastric cancer, a randomized trial finds.

Environmental factors play an important role in gastric cancer; for example, infection with the bacterium Helicobacter pylori is a known cause of gastric cancer. Some studies have suggested that a diet rich in fruit and vegetables decreases the risk of gastric cancer, perhaps because such foods contain antioxidants.

To determine the effect of antioxidant supplements on gastric cancer risk, Martyn Plummer, of the International Agency for Research on Cancer, and colleagues conducted a randomized clinical trial among 1980 people in Tachira State, Venezuela, whose population is at high risk of gastric cancer. Participants were randomly assigned to receive a placebo or a combination of the antioxidants vitamin C, vitamin E, and beta-carotene.

Over the 3 years of the study, all participants had several gastroscopies, or examinations of the stomach using a thin, lighted tube. During the gastroscopies, doctors took small tissue samples from specific areas of the stomach. The researchers found that antioxidant supplementation did not make a difference in the progression rate or regression rate of precancerous gastric lesions. "Supplementation with antioxidant micronutrients is not an effective tool for gastric cancer control in this high-risk population," the authors conclude.

"Disappointingly, this must be considered a negative trial," writes editorialist Philip R. Taylor, M.D., Sc.D., of the National Cancer Institute. "The way forward will require continued etiologic research to identify new modifiable factors, such as bioactive food components or other alterable environmental factors, as well as a search for beneficial associations with drugs. However, this overall effort should continue to emphasize randomized controlled trials as the most powerful and valid approach for testing specific prevention strategies and follow lessons and leads from the first generation of cancer prevention interventions."