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Human vitamin E requirements assessed with the use of apples fortified with deuterium-labeled -tocopheryl acetate^1,2,3

¹ From the Department of Food Science and Technology, Oregon State University, Corvallis, OR

Background: Little is known about factors that modulate dietary -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 -tocopherol kinetics at a dosage of -tocopherol found in food.

Design: Apples fortified with deuterium-labeled -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 -tocopherol.

Results: Compared with observations in the 0% fat trial, the maximum observed plasma d₆--tocopherol concentrations (C_max) 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--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 C_max (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 -tocopherol concentrations, the estimated daily plasma -tocopherol efflux was 13–14 mg. The estimated rate of -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.

Key Words: -Tocopherol • vitamin E requirements • bioavailability • deuterium • biokinetics • dietary fat

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