Comparison of supplementation of RRR-alpha-tocopherol and racemic alpha-tocopherol in humans. Effects on lipid levels and lipoprotein susceptibility to oxidation.

It has been suggested that alpha-tocopherol, a safe and effective antioxidant, be used in clinical trials to evaluate the ability of antioxidant therapy to inhibit atherosclerosis. Recent reports, however, have raised the possibility that there may be greater enrichment of plasma low density lipoprotein (LDL) in alpha-tocopherol resulting from the use of the naturally occurring RRR-alpha-tocopherol isomer compared with the other isomers present in the synthetic racemic form of alpha-tocopherol. Therefore, we fed equal dosages (1,600 mg/day) of the two forms of vitamin E to 16 men and women for 8 weeks and compared the effects of this supplementation on the susceptibility of isolated lipoproteins to oxidation. Neither form of vitamin E had appreciable effects on lipid or lipoprotein levels. alpha-Tocopherol levels in LDL increased at a similar rate in both groups and were nearly twofold higher than baseline levels by the end of the study. The susceptibility of LDL to oxidation was measured by formation of ...