Inter- and intra-individual variation in plasma and red blood cell vitaminE after supplementation

To establish the range of individual blood responses to supplemental vitami n E, 30 healthy subjects ingested 75mg of deuterium-labelled alpha-tocopher ol with a standard breakfast. Blood was collected at 6, 9, 12, 27 and 51 h post ingestion and deuterated (d(6)) and nondeuterated (d(0)) alpha-tocophe rol concentrations were determined in plasma and red blood cells (RBC) by G C-MS. To examine intra-individual responses, 6 df these subjects were re-ex amined at 6-month intervals over a 30-month period. Post ingestion, the amo unt of d(6)-alpha-tocopherol in blood increased rapidly with time with maxi mal concentrations seen at 12h (plasma) and 27h (RBC) in most subjects. At these times, d(6)-alpha-tocopherol concentration ranged from 0.3-12.4 mu mo l/l in plasma and 0.6-4.09 mu mol/l packed cell in RBC. Area under the curv e calculations indicated inter-individual differences of alpha-tocopherol u ptake to be 40-fold for plasma (12.9-493.3 mu molh/l) and 6-fold for RBC (2 4.4-146.1 mu molh/l packed RBC). Intra-individual variation in alpha-tocoph erol uptake was small in comparison and remained relatively constant over t he 30-month period. We conclude that vitamin E uptake varies widely in the normal population, although it is comparatively stable for an individual ov er time. These differences likely arise from variations in the regulation o f vitamin E uptake and metabolism between subjects. Factors regulating this process must be better understood before the optimal intake of vitamin E c an be ascertained.