Does breastfeeding cause cavities?

You take your toddler in for a checkup, the dentist finds a cavity or two, and the first question is whether you still breastfeed. It is hard not to hear that as blame — especially when you've been careful about sugar and you brush every day. Read up on it afterward, and even the experts seem to disagree.

The science is genuinely split

On one side, a 2021 study found that nursing at night past about 18 months raises the risk of early cavities — "breastfeeding at night from 18 months onwards is considered a risk factor for ECC," meaning early childhood caries, the term for cavities in very young children.¹ The reason given is that a baby who feeds often through the night bathes the teeth in milk while no one is there to clean them.

On the other side, a review in the Journal of the American Dental Association looked at the same question and concluded that "the relationship between unrestricted (ad libitum) breastfeeding and an increased risk of developing caries is equivocal" — equivocal meaning the studies don't point clearly one way.² The same review notes that breastmilk on its own isn't clearly the cause, and that everyday brushing may matter more than how often a baby nurses.

What everyone actually agrees on

Breastfeeding is good for your baby, teeth included — the American Academy of Pediatrics says "breastfeeding during a child's first year can help reduce the risk of tooth decay by half."³ The pediatric dentists encourage breastfeeding "as long as mutually desired," and place the cavity risk specifically on "breastfeeding and bottle use beyond 12 months, especially if frequent and/or nocturnal."⁴ Both sides point to the same thing: milk left sitting on the teeth overnight, on teeth that never get wiped or brushed.

What to do: clean the teeth, keep nursing

The useful response is to clean the teeth after the last feed of the night, so the day doesn't end with milk sitting on them. If your toddler still wakes to nurse, wipe the teeth with a clean cloth or brush them when you can: the milk is what needs to come off, and the nursing can continue. A small smear of fluoride toothpaste, the size of a grain of rice, is enough at this age.

If there's already a cavity

A cavity that has already turned up is not a verdict on your parenting. Some children are simply more prone to decay than others, for reasons as ordinary as the bacteria they happened to pick up or the depth of the grooves in their teeth. There are also gentle ways to treat a small cavity in a toddler without a drill — a brush-on liquid that stops it from growing is often the first option.

If the breastfeeding question has been weighing on you, bring it up at the next visit. We can look at your child's risk and work out a plan that protects their teeth without asking you to give up something that's working.