Human requirements
Studies have shovm that the human requirement of vitamin Bs for adults is related to the level of protein intake and is amply satisfied at the level of 0.02 mg per gram of protein.92,93 On this basis the Food and Nutrition Board30 set the recommended dietary allowances for adults at 2.0 mg per day for women and 2.2 mg per day for men. These levels would permit protein intakes of 100 g by women and 110 g by men. The vitamin Bs requirement is high in pregnancy, due to the increased need of protein, increased catabolism of tryptophan as a result of hormonal influence, and the active transport ofthe vitamin to fetal blood by the placenta. Thus an allowance of 2.6 mg per day is recommended during pregnancy; the allowance for lactating women is 2.5 mg. A complete list of the recommended dietary allowances for each age and sex group.
Al though the vi tamin Bs requirement of some bu t not all users of oral contraceptive agents may be slightly higher than that of nonusers,94 the Food and Nutrition Board concluded that current evidence does not justifY routine supplementation by all users. Biochemical evidence of marginal vitamin Bs status has been observed in the elderly95 and in chronic alcoholics, 9S but whether these groups have a higher vitamin Bs requirement than the rest of the population has not been established
