Comparison of the postprandial plasma vitamin A response in young and older adults.

To assess the influence of age on vitamin A intestinal and liver metabolism in humans, the postprandial plasma concentrations of intestinal-originated vitamin A, i.e., retinyl esters, and liver-originated vitamin A, i.e., retinol, were compared in eight young (20-30 years old) and eight elderly (64-72 years old) healthy men. Plasma and chylomicron retinyl esters and retinol concentrations were measured for up to 24 h following the intake of a test meal that contained 23,300 RE retinyl palmitate. The chylomicron retinyl palmitate response (area under the curve) was not significantly different between the two groups, but its peak was slightly delayed (1 h) in the elderly men. The proportion of the different retinyl esters secreted in the chylomicrons was not significantly different between the two groups. The postprandial plasma retinol concentration did not change in the young participants, whereas it significantly increased in the elderly. These results suggest that vitamin A intestinal absorption and retinol intestinal esterification processes are not markedly modified in the elderly, whereas the chylomicron clearance and the regulation of postprandial plasma retinol concentration are apparently altered in these subjects.