Low vitamin B-6 status in infants breast-fed exclusively beyond six months

Our aim was to ascertain the adequacy of human milk as the sole source of vitamin B-6 and the associations between maternal and infant status during extended exclusive breast-feeding. Vitamin B-6 status was followed in lactating mothers and their exclusively breastfed infants by determinations of erythrocyte pyridoxal 5'-phosphate concentration and the erythrocyte aspartate transaminase stimulation test at 2 months (n = 118), 4 months (n = 118), 6 months (n = 112), 7.5 months (n = 70), 9 months (n = 36), 10 months (n = 14), 11 months (n = 11), and 12 months (n = 7) postpartum. Of the mothers, 54% had used vitamin B-6 supplement during pregnancy, and all received a pyridoxine hydrochloride supplement of 1 mg/day throughout lactation. The infants had a higher vitamin B-6 status than their mothers. During the first 4 months, infant vitamin B-6 status was generally adequate independently of the actual vitamin status of the nursing mother. Most of the infants with low status at 2 months were those born to mothers who were not supplemented during pregnancy. By 6 months of exclusive breast-feeding, 30% of cases of low vitamin B-6 status in nursing mothers were reflected in their infants. Thereafter, the risk of low vitamin B-6 status in exclusively breast-fed infants increased even if the mother's status was adequate. Our findings suggest that gestationally accumulated stores are important for the maintenance of adequate vitamin B-6 status of infants during the early months and that for some infants, human milk alone, without supplementary foods, may be insufficient to meet vitamin B-6 needs after 6 months of age.