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

Abstract

The available evidence indicates that γ-tocopherol has more potential for colon cancer prevention than α-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 α-tocopherol at baseline was positively predicted by dietary intakes of synthetic vitamin E in foods and supplements but not by natural α-tocopherol from foods. For serum γ-tocopherol, dietary γ-tocopherol was not a predictor, but dietary α-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 α- and γ-tocopherol in colon. The Mediterranean intervention increased intakes of natural α-tocopherol, which is high in nuts, and decreased intakes of γ-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.

ACKNOWLEDGMENTS

We thank all the individuals who volunteered for the Healthy Eating Study for Colon Cancer Prevention. Mary Rapai, MS, was the coordinator for the study and Maria Cornellier, RD, MS, was the study dietitian. We thank Gary Schneider, Megan Rook and Thomas Ferreri for assistance with data management and Angela Glazier for assistance with manuscript preparation.

FUNDING

This study was supported by NIH grants RO1 CA120381, P30 CA130810 S1 and Cancer Center Support Grant P30 CA046592. The study used core resources supported by a Clinical Translational Science Award, NIH grant UL1RR024986 (the Michigan Clinical Research Unit), by the Michigan Diabetes Research and Training Center NIH grant 5P60 DK20572 (Chemistry Laboratory), and by the Michigan Nutrition and Obesity Research Center NIH grant P30 DK089503. The study was registered on the Clinical Trials website maintained by the National Institutes of Health, registration number NCT00475722.