Iodine in human milk.

To determine the iodine concentration of human milks, total expressions were collected from eight subjects, and partial expressions from either breast before and after nursing were collected from another eight subjects. Three of the second eight partial expressions were collected before and after nursing so that the iodine concentration of milk collected at these times could be compared. Iodine in total expressions was measured by an ion-selective electrode procedure and in partial expressions by a microchemical procedure. Differences between iodine concentrations of milks collected before and after nursing or of milks from left or right breast were not significant. Milk iodine concentrations for the 16 subjects, ranging from 21 to 281 micrograms/kg and averaging 142 micrograms/kg, compare favorably with data collected in 1933.