α-Tocopherol disappearance rates from plasma depend on lipid concentrations: studies using deuterium-labeled collard greens in younger and older adults.
Am J Clin Nutr. 2015 Apr ;101(4):752-9. Epub 2015 Mar 4. PMID: 25739929
Maret G Traber
BACKGROUND: Little is known aboutα-tocopherol's bioavailability as a constituent of food or its dependence on a subject's age.
OBJECTIVE: To evaluate theα-tocopherol bioavailability from food, we used collard greens grown in deuterated water ((2)H collard greens) as a source of deuterium-labeled ((2)H) α-tocopherol consumed by younger and older adults in a post hoc analysis of a vitamin K study.
DESIGN: Younger (mean± SD age: 32 ± 7 y; n = 12 women and 9 men) and older (aged 67 ± 8 y; n = 8 women and 12 men) adults consumed a test breakfast that included 120 g (2)H collard greens (1.2 ± 0.1 mg (2)H-α-tocopherol). Plasma unlabeled α-tocopherol and (2)H-α-tocopherol were measured by using liquid chromatography-mass spectrometry from fasting (>12 h) blood samples drawn before breakfast (0 h) and at 24, 48, and 72 h and from postprandial samples collected at 4, 5, 6, 7, 9, 12, and 16 h.
RESULTS: Times (12.6± 2.5 h) of maximum plasma (2)H-α-tocopherol concentrations (0.82% ± 0.59% total α-tocopherol), fractional disappearance rates (0.63 ± 0.26 pools/d), half-lives (30 ± 11 h), and the minimum estimated (2)H-α-tocopherol absorbed (24% ± 16%) did not vary between age groups or sexes (n = 41). Unlabeled α-tocopherol concentrations were higher in older adults (26.4 ± 8.6 μmol/L) than in younger adults (19.3 ± 4.2 μmol/L; P = 0.0019) and correlated with serum lipids (r = 0.4938, P = 0.0012). In addition, (2)H-α-tocopherol half-lives were correlated with lipids (r = 0.4361, P = 0.0044).
CONCLUSIONS: Paradoxically,α-tocopherol remained in circulation longer in participants with higher serum lipids, but the (2)H-α-tocopherol absorbed was not dependent on the plasma lipid status. Neither variable was dependent on age. These data suggest that plasma α-tocopherol concentrations are more dependent on mechanismsthat control circulating lipids rather than those related to its absorption and initial incorporation into plasma. This trial was registered at clinicaltrials.gov as NCT0036232.