Vitamin A uptake from foods

PURPOSE OF REVIEW: To review our current understanding of vitamin A uptake from foods. RECENT FINDINGS: There are advancements in understanding the molecular processes involved in vitamin A uptake and the regulation of these processes. A number of genes involved in vitamin A transport and metabolism have been recently identified. The identification of mutations in human genes and targeted disruption of mouse genes have provided further insight as to how these genes contribute to meeting nutritional needs. SUMMARY: The rate limiting steps in the lymphatic absorption of vitamin A involve intracellular processing of vitamin A within the enterocyte. The key steps appear to be related to chylomicron formation and secretion and are closely coupled with fat absorption. The genes encoding serum retinol binding protein, cellular retinol binding protein I and cellular retinol binding protein II have been disrupted by homologous recombination in mice. Studies of these knockout mice indicate that extrahepatic uptake of postprandial vitamin A may play a particularly important role in the maternal-offspring transfer of vitamin A. Further studies of the transfer of maternal dietary vitamin A have important implications for assessing the upper limits of maternal vitamin A supplementation.