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By Maria Morava
Relationships Reporter
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Kids who are exclusively breast-fed as infants are less likely to experience early puberty.
This is the conclusion of South Korean researchers who studied the development and infant diets of more than 300,000 children.
The team found that breastfeeding during the first four–six months of life was linked with a lower risk of so-called "central precocious puberty" (CPP) in both boys and girls. This association was partially mediated by differences in body weight throughout childhood, with childhood obesity linked to early pubertal onset.
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While it can lead to an early growth sport compared to other children, adults who went through early puberty tend to be shorter on average. CPP has also been linked to an increased risk of anxiety, depression and low self-esteem.
Early puberty has also been associated with an increased risk of substance abuse, eating disorders and having sex at an early age. In women, early puberty is also known to increase the risk of breast cancer as adults.
CPP has been on the rise globally, a trend that doctors Lin Yang and Shengxu Li—who were not involved in the study, but authored an accompanying comment paper—say is "particularly concerning given the growing prevalence of childhood obesity."
The findings, the researchers note, add to the growing body of evidence highlighting the critical role of early-life nutrition in long-term health.
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In this nationwide, retrospective study, researchers compared the incidence of early puberty among children who were exclusively breastfed, formula-fed or mixed-fed during their first four to six months of life.
Compared to exclusively breastfed children, formula-fed children had the greatest risk of CPP in boys and girls, followed by mixed-fed boys and girls.
In their commentary paper, Yang and Li noted that the findings "contradict prior claims that breastfeeding is unrelated to the timing of pubertal onset in non-Western settings."
They explained that the study's findings "suggest a potential developmental pathway through which infant feeding may influence early weight gain and the subsequent pubertal timing."
However, they also acknowledged that the source of these associations remains uncertain, and that it is not yet clear whether excess body fat directly contributes to the activation of the hypothalamic-pituitary-gonadal axis—a hormonal pathway that regulates reproduction and development—or regulates upstream signals like the hypothalamic kisspeptin system, responsible for regulating the onset of puberty.
The duo highlighted the study's importance in filling a research gap on puberty timing in boys. They noted: "Boys who were exclusively formula-fed had a 16 percent increased risk of CPP compared with those who were exclusively breastfed, and [excess body fat] mediated this association in a pattern similar to that observed in girls."
The experts pointed out that this increase in CPP risk observed in boys contrasts with the 60 percent increase observed in girls—which might help explain the lack of similar reports on puberty timing in boys.
Ultimately, the study's findings support the view that breastfeeding during early infancy may help protect against CPP in both sexes.
As Yang and Li concluded: "Disease starts early, so should its prevention."
Do you have a tip on a health story that Newsweek should be covering? Do you have a question about CPP? Let us know via health@newsweek.com.
References
Choe, Y., Ryu, S., Choi, J., Na, J. Y., Lee, K. S., Kim, Y. J., & Yang, S. (2025). Breastfeeding, prepubertal adiposity, and development of precocious puberty. JAMA Network Open, 8(8). https://doi.org/10.1001/jamanetworkopen.2025.27455
Yang, L., & Li, S. (2025). Breastfeeding, adiposity, and precocious puberty in boys and girls. JAMA Network Open, 8(8). https://doi.org/10.1001/jamanetworkopen.2025.27461
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