Y-Tocopherol, the major form of vitamin E in the US diet, deserves more attention Review

摘要

gamma -Tocopherol is the major form of vitamin E in many plant seeds and in the US diet, but has drawn little attention compared with alpha -tocopherol, the predominant form of vitamin E in tissues and the primary form in supplements. However, recent studies indicate that gamma -tocopherol may be important to human health and that it possesses unique features that distinguish it from alpha -tocopherol. gamma -Tocopherol appears to be a more effective trap for lipophilic electrophiles than is alpha -tocopherol. gamma -Tocopherol is well absorbed and accumulates to a significant degree in some human tissues; it is metabolized, however, largely to 2,7,8-trimethyl-2-(beta -carboxyethyl)-6-hydroxycluoman (gamma -CEHC), which is mainly excreted in the urine. gamma -CEHC, but not the corresponding metabolite derived from alpha -tocopherol, has natriuretic activity that may be of physiologic importance. Both gamma -tocopherol and gamma -CEHC, but not alpha -tocopherol, inhibit cyclooxygenase activity and, thus, possess antiinflammatory properties. Some human and animal studies indicate that plasma concentrations of gamma -tocopherol are inversely associated with the incidence of cardiovascular disease and prostate cancer. These distinguishing features of gamma -tocopherol and its metabolite suggest that gamma -tocopherol may contribute significantly to human health in ways not recognized previously. This possibility should be further evaluated, especially considering that high doses of alpha -tocopherol deplete plasma and tissue gamma -tocopherol, in contrast with supplementation with gamma -tocopherol, which increases both. We review current information on the bioavailability, metabolism, chemistry, and nonantioxidant activities of gamma -tocopherol and epidemiologic data concerning the relation between gamma -tocopherol and cardiovascular disease and cancer.