title: Plasma carotenoid levels in human subjects fed a low carotenoid diet.
abstract: The purpose of this study was to investigate the effect of a low carotenoid diet on plasma carotenoid levels in humans. Twelve healthy male subjects were fed a low carotenoid diet under controlled conditions for 13 wk in a live-in metabolic unit, as part of a study of vitamin C requirement. Plasma carotenoids (zeaxanthin/lutein, cryptoxanthin, lycopene, alpha-carotene, beta-carotene) were measured with HPLC on study days 2-3, 14-15, 35-36 and 63-64. The rate of decline was rapid between d 2-3 and d 14-15, when the concentration of each carotenoid decreased significantly (P less than 0.05). Although accurate figures for half-life are not possible without more frequent sampling points, mean plasma depletion half-life seemed to be less than 12 d for beta-carotene, alpha-carotene and cryptoxanthin, between 12 and 33 d for lycopene and between 33 and 61 d for zeaxanthin/lutein. Because the decline was not linear over the study period, these data suggest the possibility of at least two body pools of these compounds, with one pool having a more rapid turnover rate. Because there is a significant decline in plasma carotenoid levels within the first 2 wk of a low carotenoid diet, determination of levels of these compounds may be useful only in the assessment of short-term intake.
authors.affiliation: School of Public Health, University of California, Los Angeles 90024.
authors.forename: C L
authors.initials: CL
authors.lastname: Rock
authors.forename: M E
authors.initials: ME
authors.lastname: Swendseid
authors.forename: R A
authors.initials: RA
authors.lastname: Jacob
authors.forename: R W
authors.initials: RW
authors.lastname: McKee
mesh_terms: D001205:Ascorbic Acid / Q000008:administration & dosage; D015415:Biomarkers; D002338:Carotenoids / Q000008:administration & dosage / Q000097:blood*; D002851:Chromatography, High Pressure Liquid; D004032:Diet; D006801:Humans; D009751:Nutritional Requirements
chemical_list: D015415:Biomarkers; D002338:Carotenoids; D001205:Ascorbic Acid