Do breastfed babies need extra water?

Ask Anne…

Question: I successfully nursed my first baby. I am now expecting my second child and plan on breastfeeding her as well.  I was told by a pediatric nurse that breast fed babies need water – about a cup a day. Is this true? I never gave my son water.

Answer: It sounds like your nurse needs a refresher course in “Breastfeeding 101.” Maybe she is more familiar with formula fed babies than she is with breastfed. Many health care providers and caregivers (especially grandmothers) who are used to formula fed babies have a really hard time accepting the fact that a baby can survive without supplemental water. The fact is: breastfed babies do not need any supplemental water, but formula fed babies often do. Formula fed babies may need water supplements due to the renal solute load of formula (the higher salt level is harder on their kidneys, and they may need extra water in order to excrete it). Formula fed babies also have less efficient metabolisms than breastfed babies, so they use up water faster.

Breast milk is composed of 90% water, and that provides all that your nursing baby needs, even in hot weather. Nursing babies that are thirsty will regulate their own intake by feeding more often and taking in enough of the watery foremilk to satisfy their thirst. They are able to regulate their own fluid intake, which is one more nice thing about breastfeeding. Supplemental feedings fill up your baby with empty calories, making him less interested in nursing.

Water supplements interfere with breastfeeding, and can actually contribute to weight loss and jaundice.  Doctors used to believe that giving a jaundiced newborn water would help ‘flush out’ the bilirubin, but now we know that this isn’t the case. Excess bilirubin is excreted through the stools, not the urine. A newborn who is supplemented with water may actually develop higher bilirubin levels, and tends to lose more weight than a baby who is not supplemented with water.

Water supplements in a newborn can also interfere with the establishment of a mother’s milk supply, and giving excessive amounts of water to a newborn (under 5 weeks old) can actually be dangerous. Too much water can dilute the sodium in the baby’s bloodstream to the point where “oral water intoxication” develops, and this can lead to symptoms like low body temp, bloating, and seizures. Once again, Mother Nature knows best. You don’t need to give your breastfed baby water.

(Updated October 2016)

Anne Smith, IBCLC
Breastfeeding Basics