This kinetic, bioavailability, and metabolism study of RRR-α-tocopherol in healthy adults suggests lower intake requirements than previous estimates

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Abstract

Kinetic models enable nutrient needs and kinetic behaviors to be quantified and provide mechanistic insights into metabolism. Therefore, we modeled and quantified the kinetics, bioavailability, and metabolism of RRR-α-tocopherol in 12 healthy adults. Six men and 6 women, aged 27 ± 6 y, each ingested 1.81 nmol of [5-14CH3]-(2R, 4'R, 8'R)-α-tocopherol; each dose had 3.70 kBq of 14C. Complete collections of urine and feces were made over the first 21 d from dosing. Serial blood samples were drawn over the first 70 d from dosing. All specimens were analyzed for RRR-α-tocopherol. Specimens were also analyzed for 14C using accelerator MS. From these data, we modeled and quantified the kinetics of RRR-α-tocopherol in vivo in humans. The model had 11 compartments, 3 delay compartments, and reservoirs for urine and feces. Bioavailability of RRR-α-tocopherol was 81 ± 1%. The model estimated residence time and half-life of the slowest turning-over compartment of a-tocopherol (adipose tissue) at 499 ± 702 d and 184 ± 48 d, respectively. The total body store of RRR-α-tocopherol was 25,900 ± 6=220 μmol (11 ± 3 g) and we calculated the adipose tissue level to be 1.53 μmol/g (657 μg/g). We found that a daily intake of 9.2 μmol (4 mg) of RRR-α-tocopherol maintained plasma RRR-α-tocopherol concentrations at 23 μmol/L. These findings suggest that the dietary requirement for vitamin E may be less than that currently recommended and these results will be important for future updates of intake recommendations. © 2012 American Society for Nutrition.

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Novotny, J. A., Fadel, J. G., Holstege, D. M., Furr, H. C., & Clifford, A. J. (2012). This kinetic, bioavailability, and metabolism study of RRR-α-tocopherol in healthy adults suggests lower intake requirements than previous estimates. Journal of Nutrition, 142(12), 2105–2111. https://doi.org/10.3945/jn.112.166462

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