throughout the first year of life. For mothers who are complete vegetarians, it is desirable to find an acceptable food source or supplement of vitamin B12 that will meet their needs and those of the nursing infant.
The full-term infant is born with adequate folate stores, even when maternal folate is suboptimal (Salmenperä et al., 1986b). The bioavailability of folate in human milk is high: to maintain equivalent folate status in formula-fed infants, approximately 50% more folate is required from formula than from human milk (Ek and Magnus, 1982). Serum and red cell folate levels are adequate in breastfed infants; indeed, they are several-fold greater than adult reference levels (Ek and Magnus, 1979; Salmenperä et al., 1986b; Smith et al., 1985). This is reported for infants exclusively breastfed for up to 1 year (Salmenperä et al., 1986b).
Maternal folate levels in serum and milk do not appear to be correlated; however, there are strong associations between maternal and infant serum folate levels at 6 weeks and at 3 months after birth (Smith et al., 1983) and at 4 and 9 months after birth (Salmenperä et al., 1986b). Those associations suggest that folate stores accumulated in utero are more important determinants of folate status during infancy than are levels of folate in milk.
Biochemical data concerning the riboflavin status of infants are difficult to interpret. Hovi and colleagues (1979) reported a transient increase in the activation coefficient of erythrocyte glutathione reductase (EGR) in full-term healthy breastfed newborns—a finding that suggests riboflavin deficiency. The increase became even greater when the infants had received phototherapy for treatment of hyperbilirubinemia (Gromisch et al., 1977; Hovi et al., 1979; Tan et al., 1978); however, this was not accompanied by clinical signs of riboflavin deficiency. The increase in the activation coefficient did not occur with daily maternal riboflavin supplements of 0.5 mg/kg of body weight, but neither was this increase evident after 2 weeks in the infants of unsupplemented women (Nail et al., 1980). The riboflavin concentration in human milk is dependent on maternal riboflavin status (Bates et al., 1982).
High EGR activation coefficients have been reported for breastfed infants who receive only 0.13 to 0.21 mg of riboflavin per day from human milk (Bates et al., 1982). The average intake of riboflavin in exclusively breastfed infants in the United States is estimated to be 0.26 mg/day. Using several criteria, including riboflavin levels in urine and blood, Snyderman and coworkers (1949) found that riboflavin intakes of 0.3 to 0.4 mg/day provide adequate riboflavin status. Among infants undergoing phototherapy, comparable intakes of riboflavin maintain normal EGR activation coefficients (Tan et al., 1978). No