Breast Milk and Tooth Decay in Babies: Separating Fact from Fiction

A friend once told me that her baby developed cavities, and she was convinced breast milk was the culprit because her little one was still breastfeeding at 18 months. She was certain that breast milk or breastfeeding for a prolonged period causes cavities and I was quite confused.

I’ve known other babies who were breastfed well into toddlerhood, and honestly, I don’t recall any of them having tooth decay. But now that I think about it, I probably never looked that closely at their teeth. So where did this idea even come from?

Is it just another way to discourage breastfeeding, pushing moms toward formula instead? Or is it really a case of “too much of a good thing”? After all, breast milk is liquid gold, and “breast is best,” right?

To be honest, I thought it was on the list of the most absurd things I’ve ever heard! But I thought to myself, let’s do some research and find out before jumping to conclusions.

Can babies get cavities?

Yes—children of all ages can develop cavities, and baby teeth are actually more vulnerable. That’s because they have thinner enamel than adult teeth, which makes it easier for decay to form. Tooth decay (also called dental caries) is, unfortunately, quite common in infants and toddlers.

What causes tooth decay?

This might not be common knowledge, but cavities are caused by specific bacteria that live in the mouth. Babies are born without the cavity-causing bacteria, but these bacteria—especially Streptococcus mutans—are passed from parents to children, often through saliva.

Once these bacteria settle in the mouth, they feed on sugars from the foods and drinks your baby consumes. As they break down these sugars, the bacteria produce acids that slowly erode tooth enamel, leading to cavities

This explains why some kids eat lots of candy but never develop cavities, which shows how important the presence and activity of these bacteria are in the process.

Fortunately, saliva plays a vital role in protecting your baby’s teeth. It helps wash away food particles and acids, neutralizing the harmful effects of bacteria. However, saliva flow slows down during sleep, giving bacteria more time to create acid and increasing the risk of tooth decay overnight

So, saliva is your baby’s natural tooth cleaning agent.

Now let’s talk about the risk of developing tooth decay. We know two things are required: bacteria and fermentable carbohydrates (or sugary food and drinks that the bacteria can feed on).

Does the amount of sugar matter? 

Yes, it does—but here’s the catch: what matters even more is how often your child consumes sugar rather than the total amount consumed. . Eating a big sugary treat once a day isn’t great, but snacking on sugary foods throughout the day is much worse for their teeth. That’s because each time sugar is eaten, it gives bacteria a chance to make acid that harms the teeth.

(Just to be clear—we’re talking about cavities here. For things like blood sugar, eating a large amount at once may be a bigger concern. But for tooth decay, frequency is the bigger issue

Does breast milk contain sugar? 

Yes, it does. Breast milk is a complex mixture of water, proteins, fats, carbohydrates, vitamins, and minerals. The carbohydrate portion includes sugars, starches, and fiber. Breast milk contains about 200 different types of sugars, with lactose being the primary sugar. Interestingly, the sugar content in breast milk changes naturally over time, whereas formula milk’s sugar content remains constant.

Most infant formulas also contain lactose, but some formulas include additional sugars like corn syrup solids, maltodextrin, or sucrose. Notably, Streptococcus mutans—the bacteria that cause cavities—may not metabolize lactose as easily as sucrose, which could impact the risk of tooth decay.

What does research say? Quite a lot, actually! The majority of studies agree that breast milk is not cariogenic—meaning it doesn’t cause tooth decay on its own. One of the most well-known pieces of research on this topic comes from dentists Dr. Brian Palmer and Dr. Harold Torney, who studied human skulls dating back 500 to 1000 years. Their findings showed that cavities were rare in baby teeth before the widespread use of baby bottles, during a time when breastfeeding (often extended) was the norm.

Several other studies have also found no direct link between breastfeeding and cavities. For example, the March/April 1999 issue of Pediatric Dentistry concluded that human breast milk is not cariogenic. This study, which examined extracted teeth and monitored pH changes in dental plaque, found no evidence that breast milk itself causes decay (Erickson, 1999).

A Finnish study published in 1990 also found no correlation between dental caries and breastfeeding among children breastfed up to 34 months (Alaluusua, 1990). Additionally, a 2013 review by Lavigne concluded there was no conclusive evidence that prolonged breastfeeding increases the risk of early childhood cavities.

Dr. Torney’s research further confirmed that there’s no correlation between early childhood dental caries (before age 2) and breastfeeding habits like frequent night feeds or feeding to sleep. He noted that under typical conditions, the antibodies in breast milk actually help destroy the bacteria responsible for tooth decay.

Breast milk has a protein called lactoferrin that can kill the bacteria causing cavities. But if a child’s teeth have tiny defects, this protection might not be enough against the bacteria and sugars in the milk.

In these children, weaning may have the opposite effect due to the absence of lactoferrin.

On the other hand, some studies suggest that moms should be aware of the potential effects of breastfeeding beyond six months. For example, a study by Dr. Karen Peres in Brazil found that children breastfed for longer than two years were nearly 2.5 times more likely to develop cavities compared to those breastfed for less than one year. The study pointed to factors such as the difficulty of cleaning teeth during nocturnal breastfeeding as a possible reason.

However, the same study also found that breastfeeding between 12 and 23 months did not increase the risk of dental caries. It also highlighted socioeconomic factors that may contribute to a higher risk of cavities in children. Other research similarly concluded that breastfeeding beyond 24 months can be associated with a greater risk of tooth decay.

Another study by Carrillo-Díaz, Ortega-Martínez, and colleagues examined the impact of breastfeeding combined with cosleeping on early childhood caries (ECC). They suggested that breastfeeding after 18 months could be a risk factor for ECC because babies often breastfeed frequently at night, and oral cleaning can be neglected while the mother is asleep, allowing cavities to develop.

Interestingly, a 1999 study by Erickson found that baby teeth immersed in breast milk actually became stronger. However, when combined with sugar, breast milk had a worse decaying effect than sugar solution alone. This suggests that if a baby’s diet contains additional carbohydrates or sugars, the risk of tooth decay increases.

So, can breastfed babies get tooth decay? Yes, they can.

Is breast milk itself the direct cause? The evidence suggests it is not. Breast milk alone does not appear to cause cavities. In fact, babies who breastfeed at night traditionally showed little to no tooth decay. The antibodies in breast milk may actually help fight the bacteria that cause cavities. Breast milk also contains lactoferrin and other compounds that may strengthen teeth.

The bigger factors are feeding habits, diet, and the presence of cavity-causing bacteria. Breastfeeding on demand, including frequent night feeds, can provide natural sugars that might fuel cavity-causing bacteria, but the risk is much higher when other fermentable carbohydrates—like sugary snacks or drinks—are introduced.

Research shows that tooth decay tends to increase when babies start eating other foods and drinks that are high in sugar, rather than from breastfeeding itself. This likely explains why prolonged breastfeeding sometimes gets linked to dental issues.

Good oral hygiene, especially before bedtime when saliva production decreases, is crucial. Not cleaning a baby’s mouth before sleep increases the risk of cavities, especially when cavity-causing bacteria and sugars are present.

A baby who is exclusively breastfed, unless genetically predisposed, generally will not develop dental caries. Babies with genetic enamel defects may be more prone to decay, especially if weaned too early and miss out on the protective benefits of lactoferrin in breast milk. Almost all cavities in infants are caused by supplemental foods, sugars, and other substances beyond breast milk. Add poor oral hygiene and the presence of Streptococcus mutans bacteria, and the risk rises significantly.

Here are 9 tips to avoid tooth decay in breastfed babies:

• Avoid sharing utensils, toothbrushes, or letting your baby/toddler put their fingers in your mouth. This helps prevent the transfer of cavity-causing bacteria.

• Don’t clean your baby’s pacifier by sucking on it yourself.

• Avoid using your breast as a pacifier. If your baby falls asleep while breastfeeding, gently remove your breast from their mouth to reduce prolonged exposure to milk sugars.

• Practice good oral hygiene yourself—your health impacts your baby’s oral bacteria too.

• Limit your baby’s sugar intake and especially the frequency of sugary snacks or drinks, as sugar feeds harmful bacteria.

• Even before your baby’s first tooth erupts, clean their gums daily using a damp washcloth or gauze.

• Begin brushing as soon as the first tooth appears. Use a wet baby toothbrush and gently brush back and forth over the tooth and along the gum line, ideally twice a day.

• After giving your baby medication, especially sweet syrups, clean their mouth to reduce sugar exposure.

• Try to minimize the amount of time sugary substances stay in contact with your baby’s teeth to reduce cavity risk.