title: Supplementation of diets with alpha-tocopherol reduces serum concentrations of gamma- and delta-tocopherol in humans.
abstract: Despite promising evidence from in vitro experiments and observational studies, supplementation of diets with alpha-tocopherol has not reduced the risk of cardiovascular disease and cancer in most large-scale clinical trials. One plausible explanation is that the potential health benefits of alpha-tocopherol supplements are offset by deleterious changes in the bioavailability and/or bioactivity of other nutrients. We studied the effects of supplementing diets with RRR-alpha-tocopheryl acetate (400 IU/d) on serum concentrations of gamma- and delta-tocopherol in a randomized, placebo-controlled trial in 184 adult nonsmokers. Outcomes were changes in serum concentrations of gamma- and delta-tocopherol from baseline to the end of the 2-mo experimental period. Compared with placebo, supplementation with alpha-tocopherol reduced serum gamma-tocopherol concentrations by a median change of 58% [95% CI = (51%, 66%), P < 0.0001], and reduced the number of individuals with detectable delta-tocopherol concentrations (P < 0.0001). Consistent with trial results were the results from baseline cross-sectional analyses, in which prior vitamin E supplement users had significantly lower serum gamma-tocopherol than nonusers. In view of the potential benefits of gamma- and delta-tocopherol, the efficacy of alpha-tocopherol supplementation may be reduced due to decreases in serum gamma- and delta-tocopherol levels. Additional research is clearly warranted.
authors.affiliation: Department of Epidemiology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21205, USA. hyhuang@jhsph.edu
authors.forename: Han-Yao
authors.initials: HY
authors.lastname: Huang
authors.forename: Lawrence J
authors.initials: LJ
authors.lastname: Appel
mesh_terms: D000368:Aged; D001205:Ascorbic Acid / Q000008:administration & dosage*; D019587:Dietary Supplements; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010919:Placebos; D024505:Tocopherols / Q000097:blood*; D024502:alpha-Tocopherol / Q000008:administration & dosage* / Q000031:analogs & derivatives*; D024504:gamma-Tocopherol / Q000097:blood*
chemical_list: D010919:Placebos; D024504:gamma-Tocopherol; D024502:alpha-Tocopherol; C479072:delta-tocopherol; D001205:Ascorbic Acid; D024505:Tocopherols