Breastfeeding and tooth decay

It's normal and common for children to breastfeed to sleep and to breastfeed through the night. However, many parents are told this is bad for their teeth.   

There are two main reasons for this opinion: 

• Research studies being misunderstood.

• Lack of knowledge about how babies take in and swallow breastmilk.  

The research into breastfeeding and oral health is still evolving. Studies have shown that breastfeeding up to 12 months protects against tooth decay.

Results about longer durations of breastfeeding are mixed. It is sometimes suggested that babies who breastfeed longer than 12 months are more likely to have decay. However, this suggestion is based on studies that didn’t take into account how much sugary foods and drinks the children also had. We know that sugary foods increase the risk of tooth decay, so a diet high in sugar is more likely to be the cause than breastfeeding.

A 2020 study found that the risk of tooth decay was not linked to breastfeeding beyond 12 months. Higher rates of tooth decay were found in children from families with low socioeconomic status and those who ate a lot of sugary foods and drinks. 

Another recent study found no significant association between tooth decay and breastfeeding beyond 24 months in children living in areas of fluoridated drinking water. This suggests that giving young children water containing flouride can reduce the risk of tooth decay.  

Overall, the research shows that when babies start eating other foods and drinks, some of which are high in sugars, this is what contributes to tooth decay, rather than breastfeeding. Experts agree that good dental hygiene and healthy eating habits are the most important ways to protect the oral health of young children.

You may also have heard that frequent nighttime breastfeeds increase the risk of tooth decay. There is no good quality research to support this idea. There is no need to limit your baby's nighttime breastfeeds to protect them against tooth decay.

Some research suggests that breastfeeding may actually protect against tooth decay, while formula may contribute to tooth decay.  

• Antibodies in breastmilk may help to reduce the growth of bacteria in the mouth (including Streptococcus mutans, the bug that causes tooth decay).  

• Lactoferrin, a protein in breastmilk, actually kills Streptococcus mutans.  

• S. mutans may not be able to use lactose, the sugar found in breastmilk, as easily as sucrose that is found in some formulas. 

• Formula has the potential to cause tooth decay. Some formulas dissolve tooth enamel, significantly reduce pH (make it acidic) and support the growth of bacteria.

There is a very big difference between sucking on a bottle and sucking on the breast.

• When a baby bottle-feeds, the milk comes out into the front of their mouth and settles around their teeth. If they fall asleep with a bottle in their mouth, the teat keeps on slowly leaking any milk left in the bottle, into the baby's mouth.
• When a baby breastfeeds, they draw the nipple into the back of their mouth and the milk comes out into their throat, causing them to swallow. No milk settles around the baby’s teeth. When a baby falls asleep at the breast, no milk is left in their mouth because there is no active sucking.

This goes against the idea that being breastfed to sleep causes tooth decay. However, it is important not to allow your baby to fall asleep with a bottle.

Archaeological studies show that tooth decay was very rare in prehistoric times, before high-sugar diets became more common. We can assume that these children were breastfed for long periods and most likely slept with their mums and breastfed throughout the night. Since tooth decay was rare, these studies provide more evidence that breastfeeding does not increase the risk of tooth decay.

A number of factors increase the chances of tooth decay: 

• Sugar intake. Limit your child’s intake of sugary foods and drinks. Drink fluoridated tap water. 

• Streptococcus mutans entering a baby’s mouth. Parents and others can give this germ to the baby without knowing it. This can happen by kissing on the mouth, sharing a toothbrush, drink or spoon with them, or by sucking on baby's dummy, thinking that this cleans it before putting it back into the child's mouth. Running it under a tap would be a safer option. 

• Lack of saliva. Saliva reduces the risk of tooth decay because it helps to wash sugars from the teeth and also reduces acidity. Saliva flow naturally reduces during sleep. Saliva flow is also reduced in asthma, prematurity, diabetes and when using some medications.  

• Mum or baby being unwell or stressed during pregnancy.

• Mum smoking during pregnancy. 

• Poor eating habits of the family.

• Poor oral and overall hygiene of the family. No matter how your baby is fed, it is important to clean their teeth properly (twice a day) once the teeth appear. Take your child for regular dental check-ups.

• Family genetics. In some cases, children are born with enamel defects that increase their risk of tooth decay.

• Other conditions. These include low birth-weight (including prematurity), malnutrition, asthma, recurrent infections and chronic diseases.  

As breastfeeding is so important for you and your child’s health, it's important to know the facts about tooth decay. It’s okay to breastfeed your baby to sleep for as long as you and your child desire.   

At the same time, it is also important to reduce the risk of tooth decay. Clean your child’s teeth carefully, drink fluoridated water, avoid sugary foods and drinks and have regular dental check-ups.