Children may develop dental cavities if they are breastfed for two years or longer, according to a study.
Researchers analysed breastfeeding behaviours and sugar consumption for 1,129 children in Pelotas, Brazil.
At age five, the children visited a dentist, and were examined for decayed, missing and filled primary tooth surfaces and severe early childhood caries, or severe cavities.
Among the children in the study, 23.9 per cent had severe cavities and 48 per cent had at least one tooth surface affected by a cavity, the CNN reported.
Children who were breastfed for two years or longer had a 2.4 times higher risk of having severe cavities, compared to those who were breastfed for less than a year.
"There are some reasons to explain such an association," said Karen Peres, lead author of the study and associate professor at the University of Adelaide in Australia.
"First, children who are exposed to breast-feeding beyond 24 months are usually those breastfed on demand and at night. Second, higher frequency of breastfeeding and nocturnal breastfeeding on demand makes it very difficult to clean teeth in this specific period," Peres said.
However, the study found that breastfeeding between 12 and 23 months did not bring with it a higher risk of cavity.
About one quarter of the children were breastfed for 24 months or longer.
Marcia Vitolo, a professor of health sciences at the Federal University of Health Sciences in Porto Alegre, Brazil, said that she too believes breastfeeding at a high frequency, as well as the amount of sugar eaten, could explain the reason for these study results.
Vitolo was not involved in this study but has done similar studies of her own.
"I believe that there is association between breastfeeding and cavities when the environment is unhealthy -- like there is a high frequency of breastfeeding during day and night and consumption of sweets and candies," she said.
The study also found an association for socioeconomic characteristics that can contribute to a higher risk of a child having dental caries. If a family had a lower income or the mother had less schooling, children had more dental cavities and were at a higher risk of having severe cavities.
The study was published in the journal Pediatrics.