Effects of Vitamin E From Supplements and Diet on Colonic alpha- and gamma-tocopherol Concentrations in Persons at Increased Colon Cancer Risk

摘要

The available evidence indicates that gamma-tocopherol has more potential for colon cancer prevention than alpha-tocopherol, but little is known about the effects of foods and supplements on tocopherol levels in human colon. This study randomized 120 subjects at increased colon cancer risk to either a Mediterranean or a Healthy Eating diet for 6 mo. Supplement use was reported by 39% of the subjects, and vitamin E intake from supplements was twofold higher than that from foods. Serum alpha-tocopherol at baseline was positively predicted by dietary intakes of synthetic vitamin E in foods and supplements but not by natural alpha-tocopherol from foods. For serum gamma-tocopherol, dietary gamma-tocopherol was not a predictor, but dietary alpha-tocopherol was a negative predictor. Unlike with serum, the data supported a role for metabolic factors, and not a direct effect of diet, in governing concentrations of both alpha- and gamma-tocopherol in colon. The Mediterranean intervention increased intakes of natural alpha-tocopherol, which is high in nuts, and decreased intakes of gamma-tocopherol, which is low in olive oil. These dietary changes had no significant effects on colon tocopherols. The impact of diet on colon tocopherols therefore appears to be limited.