A longitudinal study of the relationship between vitamin A supplementation and plasma retinol, retinyl esters, and liver enzyme activities in a healthy elderly population

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Abstract
This study examined the association between dietary supplementation with vitamin A and biochemical symptoms of toxicity in 116 healthy elderly volunteers (47 male, 69 female), aged 64–88 y. Plasma retinol and retinyl ester concentrations, seven liver-function tests, and dietary and supplemental vitamin A intakes were measured annually for 5 y. Supplemental intake range was 0–47 000 IU/d; dietary intake range was 252823 032 IU/d. Fasting retinol and retinyl ester concentrations were determined by HPLC and dietary intake was assessed by a 3-d food record. Supplemental vitamin A intake was highly correlated with retinyl ester concentrations (r = 0.74, P = 0.0001). Retinyl esters ranged from 3.4% to 10.2% of retinol concentrations. Retinyl ester concentrations did not increase over time, regardless of supplement amount. The association of retinyl esters and liver-function tests was significant only for aspartate aminotransferase activity in females (r = 0.47, P = 0.0001). The supplementation amount in this study was not associated with vitamin A toxicity.