Abstract
We developed a compartmental model that describes the intestinal and post‐absorptive conversion of beta‐carotene (βC) to vitamin A (VA) in well‐nourished Chinese and US adults. After [2H8]βC was orally administered (Chinese: n=12; 55 ± 4 y; mean ± SD and US: n=9; 60 ± 8 y), data for serum [2H4]retinol from 3 h to 56 d were analyzed using WinSAAM. Data were initially fit to a 6‐compartment model representing digestion, absorption, intestinal processing, and appearance in serum of [2H4]retinol from βC. Tracer response curves indicated that postabsorptive conversion of βC occurred between 1 and 6 d. Adding a 2nd (or 3rd) delay element during the postabsorptive conversion provided the best fit to the observed data for all individuals in both groups. We hypothesize that the additional delays represent hepatic conversion of βC to VA. The time for appearance of labeled VA in serum following postabsorptive conversion averaged 9.4 ± 5.3 d (range 2.4–22.3 d) and efficiency of bioconversion ranged from 1.5–99.5%. Our model provides novel information about whole‐body VA kinetics in humans following βC administration. (Chinese National Natural Science Foundation #30271121 and USDA #51000‐065)
Published Version
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