Over 400 people participated in the study, which saw them receive either placebo or a antioxidant-rich supplement containing selenomethionnine, zinc, and vitamins A, C, and E. At the end of the study people in the antioxidant group experienced a 40 per cent reduction in the incidence of new polyps of the large bowel.
“Our study is the first intervention trial specifically designed to evaluate the efficacy of the selenium-based antioxidant compound on the risk of developing metachronous adenomas,” said lead researcher Luigina Bonelli, MD, from Italy’s National Institute for Cancer Research in Genoa.
The study represents another step on the ladder of supporting the potential anti-cancer effects of the mineral. Earlier this year, the US Food and Drug Administration said there is “no credible evidence” to support qualified health claims for selenium dietary supplements and a reduced risk of urinary tract cancers other than bladder cancer, lung and other respiratory tract cancers, colon and other digestive tract cancers, brain cancer, liver cancer, or breast cancer.
The research findings are being presented at the American Association for Cancer Research Frontiers in Cancer Prevention Research Conference, held in Houston. NutraIngredients has not seen the full data.
Adenomatous polyps (or adenoma) are benign lesions of the large bowel that, in time, could progress to cancer, explain the researchers. Even though only a small proportion of adenomas will develop into cancer, it is said that almost 70 to 80 per cent of colorectal cancer stems from an adenoma.
Study details
Bonelli and her co-workers randomly assigned the 411 participants aged between 25 and 75 to receive either placebo or the antioxidant supplement. The supplement provided daily doses of 200 micrograms of selenomethionnine, 30 milligrams of zinc, 6,000 IU of vitamin A, 180 milligrams of vitamin C, and 30 milligrams of vitamin E. All the participants had already undergone surgery to remove one or more colorectal adenomas.
“Our results indicated that individuals who consumed antioxidants had a 40 per cent reduction in the incidence of metachronous adenomas of the large bowel,” said Bonelli. “It is noteworthy that the benefit observed after the conclusion of the trial persisted through 13 years of follow up.”
Selenium and prostate health – controversial or convincing?
While the science may be lacking for selenium and colon health, a greater body of science exists for the mineral and prostate health. However, this subject is controversial. A number of studies, most notably the Nutritional Prevention of Cancer study and the Alpha-tocopherol, Beta-carotene Cancer Prevention study, have reported that the nutrients, alone or in combination, may reduce the risk of prostate cancer.
With over half a million new cases of prostate cancer are diagnosed every year world wide, and the cancer directly causing over 200,000 deaths, potential preventive measures are highly desirable. Despite great promise over vitamin E and selenium, recent results from the Selenium and Vitamin E Cancer Prevention Trial (SELECT) reported no significant differences between any of the groups in relation to prostate cancer risk.
The results were greeted with disappointment, while many in both academia and industry indicating that, given positive results from previous clinical trials and epidemiological studies, the design of SELECT, including the supplements used, may have undermined the results.