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Nutrition During Lactation
longitudinal studies of representative populations have been conducted in developed countries to determine the adequacy of riboflavin status among breastfed infants. No reports of riboflavin deficiency among exclusively breastfed infants in the United States were encountered in the review of the literature by the subcommittee.
Iron deficiency and iron deficiency anemia remain important problems in the United States and the rest of the world. The estimated worldwide prevalence of anemia in children from birth to age 4 years is 43%. There are remarkable differences in the prevalence rates of iron deficiency anemia in economically developed regions (~12%) and developing areas (~51%) of the world (FAO, 1988). In the United States, children aged 1 to 2 years have a higher prevalence of iron deficiency (9.3%) than do people in other age groups (DHHS, 1988). Although inadequate iron intakes are not the sole cause of anemia in infants and children, diets low in iron play a major etiologic role.
A heavy demand is placed on the iron reserves of breastfed infants: the estimated daily physiologic requirement is 0.7 mg for growth and 0.2 mg to replace basal losses (Dallman, 1986). Human milk provides from 0.15 to 0.68 mg of iron per day. Approximately 50% of iron is absorbed from human milk compared with 7% from iron-fortified formula and 4% from infant cereals (Dallman, 1986). The iron concentration in milk is not influenced by the mother's iron status (Dallman, 1986; Murray et al., 1978; Siimes et al., 1984). Body stores of iron and ferritin levels increase during the first 3 months of postnatal life and then drop during the fourth to sixth months (Duncan et al., 1985; Garry et al., 1981; Saarinen et al., 1977). Despite those changes, iron deficiency is uncommon in breastfed infants during their first 6 months (Duncan et al., 1985; Garry et al., 1981; Owen et al., 1981; Picciano and Deering, 1980; Saarinen and Siimes, 1979a; Saarinen et al., 1977).
Woodruff and colleagues (1977) suggest that partially breastfed infants younger than 6 months are at risk of iron deficiency: they found a hemoglobin level lower than 11.0 g/dl in 1 of 12 breastfed infants and a transferrin saturation of less than 16% in 4 of them. Mothers in that study were instructed to feed supplementary foods to the infants at age 3 months; foods high in iron content were offered in limited amounts. Supplementary foods lead to decreased intake of human milk and possibly impair the absorption of iron from human milk (Oski and Landaw, 1980).
Two studies of a total of 43 infants indicated that there is a risk of iron deficiency by age 9 months if human milk is the infant's only food (Pastel et al., 1981; Siimes et al., 1984). Therefore, foods with bioavailable iron,