α-Tocopherol disappearance rates from plasma depend on lipid concentrations: studies using deuterium-labeled collard greens in younger and older adults

To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by the American Society for Nutrition and can be found at: http://ajcn.nutrition.org/.BACKGROUND: Little is known about α-tocopherol’s bioavailability\ud as a constituent of food or its dependence on a subject’s age.\ud OBJECTIVE: To evaluate the α-tocopherol bioavailability from food,\ud we used collard greens grown in deuterated water (²H collard\ud greens) as a source of deuterium-labeled (²H) α-tocopherol consumed\ud by younger and older adults in a post hoc analysis of a vitamin\ud K study.\ud DESIGN: Younger (mean ± SD age: 32 ± 7 y; n = 12 women and\ud 9 men) and older (aged 67 ± 8 y; n = 8 women and 12 men) adults\ud consumed a test breakfast that included 120 g ²H collard greens\ud (1.2 ± 0.1 mg ²H-α-tocopherol). Plasma unlabeled α-tocopherol\ud and ²H-α-tocopherol were measured by using liquid chromatography–mass spectrometry from fasting (>12 h) blood samples drawn before\ud breakfast (0 h) and at 24, 48, and 72 h and from postprandial\ud samples collected at 4, 5, 6, 7, 9, 12, and 16 h.\ud RESULTS: Times (12.6 ± 2.5 h) of maximum plasma ²H-α-tocopherol\ud concentrations (0.82% ± 0.59% total α-tocopherol), fractional disappearance\ud rates (0.63 ± 0.26 pools/d), half-lives (30 ± 11 h), and\ud the minimum estimated ²H-α-tocopherol absorbed (24% ± 16%) did\ud not vary between age groups or sexes (n = 41). Unlabeled α-tocopherol\ud concentrations were higher in older adults (26.4 ± 8.6 μmol/L) than\ud in younger adults (19.3 ± 4.2 μmol/L; P = 0.0019) and correlated with\ud serum lipids (r = 0.4938, P = 0.0012). In addition, ²H-α-tocopherol\ud half-lives were correlated with lipids (r = 0.4361, P = 0.0044).\ud CONCLUSIONS: Paradoxically, α-tocopherol remained in circulation longer\ud in participants with higher serum lipids, but the ²H-α-tocopherol\ud absorbed was not dependent on the plasma lipid status. Neither\ud variable was dependent on age. These data suggest that plasma\ud α-tocopherol concentrations are more dependent on mechanisms that\ud control circulating lipids rather than those related to its absorption\ud and initial incorporation into plasma. This trial was registered at\ud clinicaltrials.gov as NCT0036232