Plasma Vitamin E Kinetics. A kinetic model of vitamin E transport in human plasma has been developed using data from studies with deuterium-labeled stereoisomers of α-tocopherol (RRR and SRR) (Traber et al., 1994b). The apparent half-life of RRR-α-tocopherol in normal subjects was approximately 48 hours, consistent with the “slow” disappearance of RRR-α-tocopherol from the plasma, whereas the half-life for SRR-α-tocopherol was approximately 13 hours. The half-life of γ-tocopherol in normal subjects has been estimated to be approximately 15 hours (Acuff et al., 1997).