Recommended dietary intakes (RDI) of vitamin A in humans.

Mean and median dietary intakes of vitamin A in the US are approximately 1000 and 624 retinol equivalents, respectively. In this paper a satisfactory vitamin A status is defined as a total-body pool that provides adequate vitamin A to meet all known physiological needs and a reserve for 4 mo on low intakes or during stress. Mean dietary intakes required to maintain an adequate body pool (ie, 20 micrograms vitamin A/g liver [0.07 mumol/g]) in reference 76-kg men and 62-kg women are 506 and 413 micrograms retinol, respectively. Recommended dietary intakes (RDI) for nearly all reference men and women are 700 micrograms and 600 micrograms, respectively. Vitamin A needs in infants, children, the elderly, and pregnant and lactating women are quantified. The toxicity of vitamin A in early pregnancy, for which a safe intake level is not known, is stressed. On many grounds these suggested lower RDI values are preferable to the 1980 RDA values.