Plasma Carotenoid Levels in Human Subjects Fed a Low Carotenoid Diet ,

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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, alphacarotene, 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 < 0.05). Although accurate figures for half-life are not possible without more frequent sampling points, mean plasma depletion half-life seemed to be <12 d for betacarotene, 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.