OBJECTIVETo investigate the iodine levels of urine from 1 month old breast-fed infants and the ones of milk and urine from the lactating women, and to observe the effects of different feeding methods (breast-feeding, mixed-feeding, bottle-feeding) on the iodine status of the infants during the weaning period in Beijing.

METHODSFrom March, 2001 to March, 2002, the iodine levels of urine from 97 breast-fed infants 1 month of age and the ones in milk and urine from lactating women were measured and compared. The infants followed up were divided into 3 groups (breast-fed, mixed and bottle-fed) until 6 months old. Their iodine levels of urine were measured and compared with the ones of 1 month of age.

RESULTSThe median value of urine iodine from breast-fed 1 month old infants was 183 micro g/L, suggesting that the infants with breast-fed had good iodine nutritional status. The median value of urine iodine from lactating women was 122 micro g/L, significantly lower than the value of milk iodine, 201 micro g/L (P < 0.001). which suggests that the lactating women were iodine deficient but could provide infants iodine adequately through breast feeding. Compared with 1 month af age, the urine iodine levels of 6 months old infants with breast-feeding increased (P < 0.001), the ones with bottle-feeding decreased significantly (P < 0.001) and the mixed-feeding group did not change (P > 0.05). The differences among 3 groups were significant (P < 0.005), the urine iodine levels of infants of both breast-feeding and mixed-feeding groups were higher than the ones of bottle-feeding. The breast-feeding group was the highest one among three groups.

CONCLUSIONThe breast-fed infants were nourished with iodine, but the lactating women were iodine deficient. Accompanied the decrease of the amount of breast milk, the iodine levels of infants urine decreased during the weaning period, some bottle-feeding infants were iodine deficient.