title: Inter- and intra-individual variation in plasma and red blood cell vitamin E after supplementation.
abstract: To establish the range of individual blood responses to supplemental vitamin E, 30 healthy subjects ingested 75 mg of deuterium-labelled alpha-tocopherol with a standard breakfast. Blood was collected at 6, 9, 12, 27 and 51 h post ingestion and deuterated (d6) and non-deuterated (do) alpha-tocopherol concentrations were determined in plasma and red blood cells (RBC) by GC-MS. To examine intra-individual responses, 6 of these subjects were re-examined at 6-month intervals over a 30-month period. Post ingestion, the amount of d6-alpha-tocopherol in blood increased rapidly with time with maximal concentrations seen at 12 h (plasma) and 27 h (RBC) in most subjects. At these times, d6-alpha-tocopherol concentration ranged from 0.3-12.4 micromol/l in plasma and 0.6-4.09 micromol/l packed cell in RBC. Area under the curve calculations indicated inter-individual differences of alpha-tocopherol uptake to be 40-fold for plasma (12.9-493.3 micromol h/l) and 6-fold for RBC (24.4-146.1 micromol h/l packed RBC). Intra-individual variation in alpha-tocopherol uptake was small in comparison and remained relatively constant over the 30-month period. We conclude that vitamin E uptake varies widely in the normal population, although it is comparatively stable for an individual over time. These differences likely arise from variations in the regulation of vitamin E uptake and metabolism between subjects. Factors regulating this process must be better understood before the optimal intake of vitamin E can be ascertained.
authors.affiliation: The Rayne Institute, St. Thomas' Hospital, King's College London, UK.
authors.forename: H E
authors.initials: HE
authors.lastname: Roxborough
authors.forename: G W
authors.initials: GW
authors.lastname: Burton
authors.forename: F J
authors.initials: FJ
authors.lastname: Kelly
mesh_terms: D000042:Absorption; D000328:Adult; D003903:Deuterium; D019587:Dietary Supplements; D004912:Erythrocytes / Q000378:metabolism*; D006801:Humans; D008297:Male; D012016:Reference Values; D014810:Vitamin E / Q000008:administration & dosage / Q000097:blood* / Q000493:pharmacokinetics*
chemical_list: D014810:Vitamin E; D003903:Deuterium