Human requirement
Elaborate studies have been made to determine human requirements for ascorbic acid at different ages, under different conditions of environment, during physical exertion, in fevers, and in infections. The amount necessary to prevent frank symptoms of scurvy in humans is far less (10 mg) than that recommended for an optimum state of health.
In the 1980 edition of the Recommended Dietary Allowances,30 the Food and Nutrition Board increased the recommended intake for adults to 60 mg per day from the 45 mg recommended in 1974. This intake level was calculated to maintain an average ascorbate body pool of 1500 mg at a daily catabolic rate of3% to 40/0 and 850/0 efficiency of absorption. Daily intake of 35 mg was recommended for infants during the first year oflife. This amount would be obtained by a breast-fed infant who consumed 850 ml of milk per day. However, 100 mg per day was recommended for the newborn during the first week of life to protect against transient tyrosinemia, which is especially common in premature infants. During pregnancy and lactation, daily intakes of80 mg and 100 mg, respectively, were recommended.
The joint FAO/WHO Expert Committee se.t somewhat lower recommendations: 30 mg for adults (men and women over 13 years), 50 mg during pregnancy and lactation, and 20 mg for infants and children up to 13 years 01d.31
These intakes in adults are usually associated with plashealth.ma ascorbate levels of:> 0.4 mg per dl and normal health. It should be noted that these recommendations were established more than a decade ago. Significant new information about ascorbic acid metabolism has since become available. Considering the possible but quantitatively unknown effects of individual variation, emotional and environmental stress, age, smoking, and oral contraceptive agents and other drugs, the Food and Nutrition Board concluded that higher intake levels were desirable and easily attainable from the average diet in the United States.
