Statistics show that people who eat diets abundant in vitamin- and mineral-rich fruits and vegetables run lower risks of developing colon cancer--an observation strengthened by research that indicates several isolated vitamins (C, D, E) and the mineral calcium may help prevent the cancer.

In a new study, Emily White, Ph.D., and colleagues from the Fred Hutchinson Cancer Research Center in Seattle examined the relationship between vitamin and mineral supplementation and colon cancer. White studied 251 men and 193 women ages 30 to 62 who developed colon cancer and a roughly equal number of controls.

Researchers interviewed subjects about their past supplement use, diet, medical history, medications, physical activity, height, weight and bowel habits. Information pertained to a 10-year period, ending two years before a diagnosis of colon cancer. The scientists then estimated each subject's average dosage of vitamins A, C, E, folic acid and calcium. Because almost all vitamin D supplementation came from multivitamin preparations, the impact of this vitamin could not be separated from the other supplements in the multivitamin.

More than 25 percent of all subjects used multivitamins for at least one year. Between 12 and 27 percent commonly took individual supplements of vitamins C, E and calcium. Few took vitamin A alone.

Men and women who took multivitamins containing nearly 100 percent of the RDA for vitamins A, C, D, E, folic acid and other B vitamins and for the minerals iron and zinc for the entire 10-year period halved their risk of colon cancer. People who took at least 200 IU of vitamin E during the 10-year period reduced their colon cancer risk by 57 percent. Vitamins A and C, folic acid and calcium supplements were linked to decreased risk, but not as strongly as multivitamins and vitamin E.

Although supplement users may generally be more health conscious, investigators did not find any significant differences between user and nonuser risk factors such as smoking, exercise and diet. Researchers' next step is determining if nutritional supplements can be used specifically to prevent colon cancer.
--Cancer Epid, Biomarkers & Prev, 6: 769-74, 1997