Tap Water vs. Bottled Water for Baby Formula

My wife and I recently decided that we would supplement our baby's breast milk with some formula. We decided to do this because at our recent pediatrician visit, the doctor told us that babies who are breastfed will often develop vitamin D deficiency. Therefore, it is common for doctors to recommend vitamin D supplements for babies. However, instead of giving our baby just vitamin D supplements, we decided to also feed her formula because it contains vitamin D as well as other nutrients such as iron. Our plan was to feed her a mixture of formula and breast milk for the baby's last night time feeding. This would have the added benefit of keeping her little tummy full for a longer period of time during the night so that she can sleep til morning.

When we went to the store to get the formula, we noticed there was also purified "baby" water on the shelf next to the formula. We were just going to use boiled tap water to mix the formula, but seeing the purified water got us thinking, "Should we use tap water or purified bottled water for our baby formula?"

We did some research and found that it really depends on your local drinking water supply. We live in Southern California, and although the tap water is probaby ok for mixing baby formula (after boiling), we decided to use the bottled water. Here's why...

According to the American Dental Association you shouldn't use water that contains a high level of fluoride to mix baby formula. This is because it can cause a condition called enamal fluorosis, which results in white lines or spots on your child's teeth. Getting some exposure to fluoride is actually good for preventing tooth decay. But some local tap water can contain too much for a baby.

So what is too much? The water you use should contain a level of fluoride less than 0.7 mg/L. How can you know what the level of fluoride is in your tap water? You have to call your local water department to find out. We didn't bother calling our water department. Instead we just decide to use the purified bottled water, which by the way has a low level of fluoride in it. So it'll give our baby the exposure to fluoride she needs but we'll know it's not too much. And it only cost us about $1 per gallon, so we figured it was worth it. Plus, since we're using purified water we don't have to worry about all the other harmful contaminants in the tap water that can't be boiled away.