Intakes of vitamins A, C, and E and use of multiple vitamin supplements may decrease the risk of colon cancer, says a new US analysis.
In the trial, data from 13 prospective cohort studies were analyzed to evaluate the associations between intakes of vitamins A, C, and E and risk of colon cancer (1). Among 676,141 men and women, 5,454 colon cancer cases were identified after 7–20 years of follow-up. The results showed that intakes of vitamins A, C and E from food only were not associated with colon cancer risk. For increased intakes of vitamin A (1,000 mcg/day), vitamin C (100 mg/day) and vitamin E (6 mg/day) from food plus supplements a significant reduction of colon cancer risk was measured. An adjustment for total intake of vitamin B9 (folate), which has shown similar disease risk reduction in earlier studies, attenuated these associations, but the decreased cancer risk with vitamins C and E remained significant. In addition, the use of multivitamins was significantly associated with colon cancer risk reduction.
The researchers said that these findings suggest that total vitamin C and E intakes may be associated with a decreased risk of colon cancer independently of total folate intake. The link between reduction of colon cancer risk and the use of multivitamins, a major source of folate and other vitamins, would deserve further research.
Among dietary factors, vitamins A, C, and E have been hypothesized to reduce the risk of colon cancer because of their potential cancer-preventing properties: vitamin A has been found to regulate receptors that suppress tumor formation, induce cell death, and enhance immune function. Vitamin C has antioxidant properties and enhances the immune system, and vitamin E prevents oxidative damage of DNA and cell membranes by scavenging free radicals. A limited number of observational studies have investigated the associations between intakes of vitamins A, C, and E and risk of colon cancer, and the results for each vitamin have been inconsistent.