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Breastfeeding and tooth decay

Been told that breastfeeding causes tooth decay?

Find out what the research says.

baby with toothbrush

It's normal and common for children to breastfeed to sleep. However, many parents are told that breastfeeding a baby to sleep is bad for their teeth.   

There are two main reasons for this opinion: 

  • Incorrect interpreting of research studies 

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

What does the research say?

Studies have shown that breastfeeding up to 12 months protects against tooth decay. Some studies also found that babies who breastfeed longer than 12 months are more likely to have decay. However, these results didn’t take into account socioeconomic status and how much sugary foods and drinks the children also had. We know that sugary foods increase the risk of tooth decay so this 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.  

These studies show 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.  

Could breastmilk protect 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. 

  • Some formulas dissolve tooth enamel, significantly reduce pH (make it acidic) and support the growth of bacteria.  

  • Formula has the potential to cause tooth decay.  

Breastfeeding is different to bottle feeding

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. Whereas 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 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 falls asleep at the breast, no milk is left in their mouth because there is no active sucking.  

This goes against the argument that is often given, that being breastfed to sleep causes tooth decay. 

Did our ancestors suffer tooth decay?

Archaeological studies of the teeth of children in prehistoric times show that there was very little decay. We assume that those who survived babyhood would have been breastfed for long periods and probably would have slept with their mothers and breastfed during the night. 

So what does cause tooth decay in babies?

A number of factors increase the chances of tooth decay: 

  • Sugar intake. Limit your child’s intake of sugary foods and drinks and 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 ill 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 once the teeth appear and to have regular dental check-ups.

  • Family genetics. In some cases there are enamel defects.

  • 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 is 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. 

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© Australian Breastfeeding Association April 2022