Night Nursing and Cavities

Extended nursing is loosely defined. In the United States, where only about a third of babies are exclusively breastfed until 3 months of age and fewer than a sixth are exclusively breastfed until 6 months of age (per the CDC), one could reasonably claim that breastfeeding beyond a year is “extended.” The American Academy of Pediatrics recommends breastfeeding for at least a year (with complementary foods after six months of age), while the World Health Organization recommends at least two years. It goes without saying, then, that a baby breastfed per the recommendations of these organizations will still be breastfeeding when teeth have come in. Some lucky parents have babies who start sleeping through the night at only a few months of age, while other mothers find themselves nursing once, twice, or even multiple times per night well beyond a baby’s first birthday. Certain sources, including La Leche League, suggest that breast milk isn’t cariogenic (cavity-causing), and even protects the teeth. Others, however, suggest that breast milk pooling in a baby’s mouth leads to early cavities, which can have significant ramifications for later oral health. What does the science say about night nursing and cavities?

One problem with finding a scientific answer to this question is that it’s difficult research to do. Case studies — reports of medical findings in a given individual — provide a limited amount of information, but aren’t a strong platform from which to derive inductive generalizations. This is because it’s difficult or impossible to establish causality in the case of an individual. As such, while there are reports in the literature of nursing caries associated with breastfeeding, these don’t support the conclusion that night nursing causes cavities.

Stronger evidence that night nursing either is or is not associated with cavity formation comes from population-level analysis. Dentist Brian Palmer, who studies ancient human skulls, concludes that there’s no connection between breastfeeding and night nursing on the grounds that 1) there isn’t evidence of cavities in ancient skulls of children, and 2) these children were probably breastfed for an extended period of time. Unfortunately, there are several problems with his theories. First, he has no proof that children were nursed at night (yes, they probably were…but he has no proof). Second, he does not take into account other aspects of diet that could significantly impact dental health. The conclusion he can reasonably draw from his research is that nursing didn’t cause cavities in children 500-1000 years ago, but it’s not possible to generalize this conclusion to today’s children because of significant dietary and lifestyle differences.

A few studies have looked at populations of modern children in an attempt to determine whether night nursing correlates with cavities. A study of children in Tehran found an association between bottle-feeding with milk at night and cavity development, but no association between breastfeeding at night and cavity development (Mohebbi et al). A study of Swedish children found that it was the intake of cariogenic food that was most associated with early cavity formation (Hallonsten et al). This finding weakens the findings of the Mohebbi study where they apply to children in the U.S. and other Western industrialized nations, because of significant dietary differences. Hallonsten also found, interestingly enough, that children who engaged in extended breastfeeding were more likely to consume cariogenic foods and have other cavity-promoting dietary habits than those who weaned at younger ages. A study of Dutch children found that frequency of breastfeeding and lack of fluoride were most associated with development of cavities (Weerheijm et al).

Note that the experimental design in the studies above is not one that allows determination of causality, only correlation. It’s possible that parents who breastfeed at night also engage in or encourage behavior x (whatever that might be), which predisposes their children to (or helps prevent) cavities.

Cavities are, of course, complicated things. There are a multitude of factors that make them more likely (bacterial colonization of the mouth, intake of cariogenic foods), as well as factors that make them less likely (dental hygiene, fluoride). Perhaps the most important question to answer in order to inform the night nursing/cavities association is whether human milk itself is cariogenic. La Leche League claims it is not, but this appears not to be supported by any particular scientific evidence, as they cite no direct research on the cariogenicity of human milk. Research evidence, in contrast, suggests that human milk is mildly cariogenic, though far less so than sugar water or soda (Bowen et al). The researchers ranked the cariogenicity of various tested substances as follows: table sugar, 1; soda (cola), 1.16 (the acid probably contributed to the increased cariogenicity as compared to table sugar); honey, 0.88; human breast milk, 0.29; cow’s milk, 0.01; distilled water, 0. The authors speculated that the increased cariogenicity of human milk as compared to cow’s milk may be due to the greater concentration of lactose in human milk, and (likely more important) the much lower concentration of dental health-supporting minerals (such as calcium and phosphate) in human milk. Based upon this research, it is unreasonable to suggest that human milk is non-cariogenic.

 

Science Bottom Line:* Human milk is approximately 1/3 as cariogenic as table sugar, and should be treated as a mildly cariogenic food. It’s probably reasonable to consider brushing a child’s teeth after a night nursing session, or at least wiping them off with gauze.

 

What do you do to help prevent nursing cavities in your night-nursing baby or toddler?

 

References:

Bowen et al. Comparison of the cariogenicity of cola, honey, cow milk, human milk, and sucrose. Pediatrics. 2005 Oct;116(4):921-6.

Hallonsten et al. Dental caries and prolonged breast-feeding in 18-month-old Swedish children. Int J Paediatr Dent. 1995 Sep;5(3):149-55.

Mohebbi et al. Feeding habits as determinants of early childhood caries in a population where prolonged breastfeeding is the norm. Community Dent Oral Epidemiol. 2008 Aug;36(4):363-9.

Palmer; B. Breastfeeding and infant caries: No connection. ABM News and Views 2000; 6(4): 27,31.

Palmer B. The Influence of Breastfeeding on the Development of the Oral Cavity: A Commentary. J Hum Lact 1998;14:93-98.

Weerheihm et al. Prolonged demand breast-feeding and nursing caries. Caries Res. 1998;32(1):46-50.