Extra Iron Spawns Free Radicals In Gut

People who take dietary iron supplements may run an increased risk of colorectal cancer, suggests recent research that draws a direct correlation between iron intake and free radical generation.

Iron was recognized as a possible carcinogen more than 35 years ago, and studies since have found that people with iron-heavy diets, such as meat eaters, have more colon cancer. Free radicals generated by iron cause DNA mutations that, in turn, can lead to carcinogenesis. Free radicals may also stimulate polyps—known tumor precursors in the colon.

Elizabeth Lund, Ph.D., of the Institute of Food Research in Norwich, England, gave a 100 mg supplement of ferrous sulfate, containing 19 mg of elemental iron, to eight men and 10 women ages 21 to 54. Most dietary iron is not absorbed, and she determined that free radical production in subjects' feces increased dramatically after supplementation.

Although Lund studied free radical generation outside the body, the same conditions exist inside the gut. It may well be that some peoples' cellular defenses are overwhelmed by iron-induced free radicals, leading to subsequent colon cancer.

—American Journal of Clinical Nutrition 1999 Feb;69:250-5