THE CLINICAL FAILURE OF VITAMIN E TO PREVENT ATHEROSCLEROSIS: IS VITAMIN E SUPPRESSING ITSELF?

Abstract

Purpose Vitamin E alpha is the only form of vitamin E (Vit E) available as a supplement. Recent clinical trials have failed to demonstrate a beneficial effect of this supplement on atherosclerosis prevention. We tested the hypothesis that exogenous Vit E alpha supplementation suppresses the concentration of the potent endogenous antioxidant Vit E gamma. Methods We performed a randomized, placebo-controlled, crossover trial in 12 type 2 diabetic subjects. Each subject participated in four study arms: placebo, low-dose (200 IU/d), medium-dose (400 IU/d ), and high-dose (800 IU/d ) vitamin E. Each vitamin dose was taken daily for 2 weeks. The protocol included an atherogenic high-fat meal. Primary outcomes were lipid standardized plasma levels of Vit E alpha and gamma. Secondary outcomes were surrogate markers of atherosclerosis (see table). The concentration of Vit E alpha demonstrated an appropriate dose response and did not alter any surrogate markers of oxidative stress, inflammation, or hypercoagulation. At all dosages, endogenous Vit E gamma was suppressed by Vit E alpha (by approximately 50%) (p Conclusion Supplementation of vitamin E in type 2 diabetic individuals did not alter any surrogate markers of atherosclerosis. The suppression by exogenous Vit E alpha of endogenous Vit E gamma reasonably explains Vit E alpha9s ineffectiveness in atherosclerosis prevention.