Water requirements of breast-fed infants in a hot climate

To estimate the water requirements of exclusively breast-fed infants in a hot climate, theoretical calculations of water requirements were made and a field study was carried out in Jamaica. Three urine samples were collected from each of 16 infants. The specific gravity of individual urine samples ranged from 1.005 through 1.015, with a mean of 1.009 (SD +/- 0.002). Corresponding values for osmolality were calculated to be 103 through 468 mOsmole/liter with a mean of 258 mOsmole/liter. The mean specific gravity for an infant ranged from 1.006 through 1.012, or 139 through 358 mOsmole/liter. The mean outdoor temperature was 27.6 C and the humidity 76%. Because the values for specific gravity were universally low it was concluded that healthy, exclusively breast-fed infants living in a hot humid climate will manage well without additional water. Additional water may be desirable during illness.