It seems that everyday we are learning more about how breastfeeding gives babies a healthy start in life, and may lower their chances of developing a number of conditions. Scientists, however, are beginning to understand the biology behind breast milk that explains why it is linked to so many health benefits. A new study has revealed that breastfeeding helps the development of immune systems in children by fostering the growth of good bacteria in their guts.

The presence of lactic acid bacteria in the intestines is important for the healthy development of the immune systems of children. In the recent study, researchers analyzed 300 children in their first three years of life. According to Medical News Today, through the use of culture-independent techniques, the team was able to extract DNA “signature sequences” of the gut bacteria and observe how they changed over time.

The results showed that there were noticeable differences in the amount of gut bacteria among infants who were breastfed past 9 months and those who were not. The amount of gut bacteria dropped between 9 and 18 months when all children had stopped breastfeeding, and began to eat other foods. It was observed that the amount of gut bacteria found was “most pronouncedly influenced by the time of cessation of breastfeeding,” the researchers wrote. There was a clear link between an increase in body mass index (BMI) and an increase in gut bacteria. “Considering previously established positive associations between rapid infant weight gain, early breastfeeding discontinuation, and later-life obesity, the corresponding microbial findings seen here warrant attention,” the researchers wrote.

This new study challenges the previous belief that gut bacteria are stable from about 12 months old by showing that these bacteria continue changing until about 3 years of age. This means there is a “window” in these early years where the gut bacteria are more vulnerable to external factors. It seems that the longer a child is breastfed, the longer the bacteria is encouraged to flourish.

Researchers hope the findings from this study will help encourage mothers to foster the development of healthy gut bacteria in their children. It could also be used to help develop more efficient infant formulas. The new findings can be added to a list of other benefits attributed to breastfeeding, including protection against inflammation and heart disease in adulthood, lowering the risk of ear infections and ADHD, and even increasing intelligence.

Source:  Bergstrom A, Skov T, Bahl M, et al. Establishment of Intestinal Microbiota during Early Life: a Longitudinal, Explorative Study of a Large Cohort of Danish Infants. Applied Environmental Microbiology. 2014