Serum concentrations of retinol and retinyl esters in adults in response to mixed vitamin A and carotenoid containing meals.

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Abstract
Previous studies using spectrophotometric methods for vitamin A analysis concluded that fasting prior to blood collection is not necessary for determining vitamin A status of children or young adult subjects. We measured the effect of mixed vitamin A and carotenoid containing meals with less than 3, 50, and 100% of the recommended dietary allowance (RDA) for vitamin A on serum concentrations of retinyl esters, retinol, and carotenoids in elderly and young adults after an overnight fast. Retinyl ester concentrations rose significantly in both age groups with a numerically higher rise over baseline in the elderly subjects: 6.0 +/− 0.9 micrograms/dl for elderly (p less than 0.001), 5.0 +/− 0.5 micrograms/dl for young (p less than 0.001) at 50% RDA; 9.0 +/− 1.3 micrograms/dl for elderly (p less than 0.001) and 6.8 +/− 1.6 micrograms/dl for young (p less than 0.05) at 100% RDA. We conclude that in both young and elderly adults, but especially in the elderly, fasting conditions are necessary for the accurate assessment of vitamin A status if spectrophotometric methods are used for measuring vitamin A.