Abstract
To improve the understanding of vitamin E kinetics, a study was conducted in which 12 healthy adults (6 men, 6 women) ingested 1.81 nmol of [5‐14C]‐RRR‐α‐tocopherol and provided serial blood samples for at least 70 days and serial urine and fecal samples for at least 20 days after the dose. Carbon‐14 enrichment of plasma, red blood cells, urine, and feces was determined by accelerator mass spectrometry. Data were analyzed by compartmental modeling. Results revealed that α‐tocopherol exists in plasma in at least 4 distinct kinetic compartments, including chylomicrons, lipoproteins, CEHC, and a very quickly absorbed form. Results also revealed that α‐tocopherol rapidly binds to red blood cell membranes in vivo. The model indicated the presence of several tissue pools with different turnover rates, including a slow turnover tissue pool which may represent deposition of vitamin E in adipose tissue. Mean absorption (±SD) was 81%±6%, and absorption ranged from 73% to 93%. Mean RRR‐α‐tocopherol loss (±SD) via urine was 2.2 μmol/d (±2.0), and loss via feces was 7.5 μmol/d (±3.7). The half‐life of RRR‐α‐tocopherol in the deep tissue pool was on average 203 days. This work was funded by the USDA and NIH.
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