The Minimum Vitamin-A Requirements of Normal Adults

Recommended dietary allowances

“…The carotenes of different foods, however, yield varying proportions of their theoretical vitamin A values to the body. Booher and coworkers (37,38) found that human beings require an average of 73 percent (61 to 84 percent) more of pure beta-carotene dissolved in oil than of pre-formed vitamin A (cod liver oil) when measured in International Units, to maintain normal dark adaptation after the depletion of bodily stores of vitamin A (5 subjects). Apparently the human being uses beta-carotene in oil less completely than does the rat.…”

Fat-Soluble Vitamins

“…body weight. The ratio of the respective effica cies of vitamin A and carotene widens as the dose is increased and this is probably true also for man (33,34,35,36). The suggestion (32) that separate standards for vitamin A and provitamin A may be needed sooner or later cannot lightly be dismissed.…”

Recommended Dietary Allowances

“…The carotenes of different foods, however, yield varying proportions of their theoretical vitamin A values to the body. Booher and coworkers (37,38) found that human beings require an average of 73 percent (61 to 84 percent) more of pure beta-carotene dissolved in oil than of pre-formed vitamin A (cod liver oil) when measured in International Units, to maintain normal dark adaptation after the depletion of bodily stores of vitamin A (5 subjects).…”