Human vitamin E requirements assessed with the use of apples fortified with deuterium-labeled α-tocopheryl acetate

Abstract

Background: Little is known about factors that modulate dietary α-tocopherol bioavailability. Objectives: The study aimed to assess the efficacy of vitamin E-fortified apples as a low-fat vitamin E delivery system, the influence of fat on vitamin E absorption, and human vitamin E requirements by using plasma α-tocopherol kinetics at a dosage of α-tocopherol found in food. Design: Apples fortified with deuterium-labeled α-tocopheryl acetate were consumed by 5 participants at a breakfast containing 0%, 6%, or 21% kcal from fat in 3 sequential trials. The trials were separated by a 2-wk washout period. Blood samples were obtained up to 72 h, and plasma was analyzed for labeled and unlabeled α-tocopherol. Results: Compared with observations in the 0% fat trial, the maximum observed plasma d6-α-tocopherol concentrations (Cmax) and the areas under the curve increased 2- and 3-fold during the 6% and 21% fat trials, respectively. The mean (±SD) estimated percentage d6-α- tocopherol absorbed increased from 10 ± 4% during the 0% fat trial to 20 ± 3% and 33 ± 5% during the 6% and 21% fat trials, respectively. The mean time to Cmax (9 ± 2 h), fractional disappearance rates (0.022 ± 0.003 pools/d), and half-lives (32 ± 4 h) did not differ significantly between the trials. With the use of fractional disappearance rates and baseline plasma α-tocopherol concentrations, the estimated daily plasma α-tocopherol efflux was 13-14 mg. The estimated rate of α-tocopherol delivery to tissues was 5 mg/d. Conclusions: Given an estimated 33% absorption, the amount of dietary vitamin E needed daily to replace irreversible losses is ≤15 mg. These estimates support the current human vitamin E requirements despite the claims that the median amount of vitamin E that Americans consume is 7 mg/d. © 2006 American Society for Nutrition.