Infant feeding practices may influence the timing of puberty in girls

A recent large-scale study published in The Journal of Nutrition indicates that infants who are exclusively breastfed for at least four months may experience delayed onset of puberty compared to those exclusively formula-fed. This finding suggests that early feeding practices could potentially influence the timeline of sexual development in girls, although no similar pattern was observed in boys.

Puberty, a critical phase of physical maturation, has been noted to be starting earlier in recent decades, particularly among girls, raising concerns about associated health risks such as type 2 diabetes, cardiovascular disease, and certain reproductive cancers. Factors such as genetics, childhood body weight, and socioeconomic status all play a role in sexual development, leading researchers to question the potential impact of infant feeding on this biological process.

Human milk is rich in hormones and nutrients absent in infant formula, prompting investigations into its long-term effects on physical growth. The research, led by Marta Pinto da Costa from the Institute of Public Health at the University of Porto, Portugal, examined data from the Generation XXI birth cohort study, which enrolled mothers at public maternity hospitals in Porto between 2005 and 2006.

The team analyzed 4,745 children from birth to adolescence, collecting data on feeding practices and conducting physical evaluations at ages six, 15, 24 months, and ten years. At ten years, nurses assessed Tanner stages, a standard scale from one to five indicating puberty progression. A score of three or higher indicates the start of puberty.

The study found that girls exclusively breastfed for at least four months had lower likelihoods of early puberty scores at age ten compared to those never breastfed. Exclusive breastfeeding was also linked with a later onset of the first menstrual cycle, though this specific association became less significant when considering body mass index, a measure of body fat based on height and weight.

The researchers speculate that hormones in human milk, like leptin, might regulate appetite and indirectly influence puberty onset by preventing early childhood obesity. While the connection between human milk feeding and delayed puberty was more pronounced in girls, the findings in boys were less conclusive, with some boys who had some human milk exposure exhibiting a lower likelihood of early puberty signs at age ten.

Overall, boys typically enter puberty later than girls, making early signs harder to detect. Nonetheless, observational data like this study highlights the potential impact of early feeding practices on girls' sexual development, warranting further research into the exact mechanisms at play.