When you're thirsty, a cold glass of water is a refreshing and healthy choice, so it seems natural to give your baby water to quench his thirst as well. But young babies generally don't need plain water; both formula and breast milk normally contain all the water your baby needs. Giving your baby too much plain water can actually have harmful health effects. Water can also blunt your baby's appetite for the breast milk or formula which he needs to grow.
Babies younger than 6 months don't need any additional water, Georgia pediatrician Dr. Jennifer Shu explains in the July 2009 edition of CNN Health. After age 6 months, you can introduce your baby to plain water, but in amounts no larger than 2 to 4 ounces per day, in most cases. After 12 months, give your baby milk with meals but water between meals.
Benefits of Water
Once your baby starts to eat more solid foods, he might develop constipation. Drinking a small amount of water could help soften stools and prevent constipation. A small amount of water between feedings can also help prevent dehydration in hot weather for babies over age 6 months. If your baby is constipated or if it's very hot outside, your baby might benefit from 6 to 8 ounces of water per day, but talk to his pediatrician before giving this much water, Dr. Shu advises.
Plain water, unlike formula or breast milk, doesn't contain a healthy balance of electrolytes such as sodium and potassium. If your baby drinks large amounts of water, he could develop an electrolyte imbalance with low sodium that can lead to brain swelling and infant seizures, in some cases. Adding more water than formula calls for to save money can also lead to water intoxication, pediatrician Dr. Alan Greene warns. In some cases, babies taking swimming lessons have swallowed enough plain water to induce hyponatremia, or low sodium levels, triggering seizures.
If your baby is vomiting or has severe diarrhea, it might seem natural to replace lost fluids with water. But giving plain water in these circumstances can also cause low sodium levels. Instead of plain water, give your baby a balanced electrolyte solution, which replaces lost minerals, if your doctor recommends withholding formula for a short time. Breast milk is generally better tolerated during gastrointestinal illnesses than formula.
Other Risks of Water
It's very rare to get sick from drinking water, but occasional outbreaks of parasitic infections or bacterial infections such as salmonella have occurred from drinking water, particularly well water. Boiling water even when using it in formula eliminates the risk. Give your baby cold water, not hot, directly from the tap; hot water can leach lead from lead pipes. Nitrates in well water can also cause blue baby syndrome in infants under 3 months; nitrites bind to hemoglobin, reducing the hemoglobin available to carry oxygen to your baby's tissues. Have your drinking water tested if you have well water; boiling or filtering doesn't remove nitrates.