Additional water is not needed for healthy breast-fed babies in a hot climate.

In Lahore, Pakistan, a community-based study was conducted to investigate whether or not it was necessary to give water to breast-fed infants. From May to November 1986, 2-4-month-old, breast-fed infants (n = 26) were selected. During the study period the maximum temperature ranged between 27.4 and 40.7 degrees C and humidity varied between 24 and 77%. Each infant was followed up for 15 days. Water was not allowed from day 1 to day 8 and water was allowed ad libitum from day 8 to day 15. All infants were subjected to a DDAVP test to estimate the renal concentrating capacity on day 15. A significant gain in weight (p < 0.001) was observed between day 1 to 8 and 8 to 15. The differences in the values of haematocrit and serum sodium between day 8 and 1 and between day 15 and 8 were not significant. This indicates that the infants were not dehydrated when water was withheld. Furthermore, no significant difference was observed for urine specific gravity between day 8 and 1, but urine specific gravity increased significantly after the administration of DDAVP (p < 0.001), indicating that, if needed, the infants could concentrate urine when water was restricted. It was concluded that 2-4-month-old, breast-fed, healthy infants showed no signs of dehydration if additional water was not given during the summer season.