The presence of lactic acid bacteria in intestinal flora is important for the healthy development of the immune system in children's early years. Now, a Danish study that tracked over 300 children in their first 3 years of life, found that longer breastfeeding encouraged lactic acid bacteria to flourish in their guts for longer.
The study, led by the National Food Institute at the Technical University of Denmark (DTU-Food) in Søborg, is published in the journal Applied and Environmental Microbiology.
Previous studies have shown that breastfed babies tend to be a little slimmer and grow more slowly than formula-fed infants. Breastfeeding has also been linked to lower risk of obesity, diabetes, inflammatory bowel disease and allergies later in life.
The new study suggests these effects may be the result of breastfeeding encouraging the development of friendly bacteria in the baby's gut.
Senior author Tine Rask Licht, professor and research manager at DTU-Food, says:
"We have become increasingly aware of how crucially important a healthy gut microbial population is for a well-functioning immune system. Babies are born without bacteria in the gut, and so it is interesting to identify the influence dietary factors have on gut microbiota development in children's first 3 years of life."
Led by Kim F. Michaelsen, a professor in the Department of Nutrition, Exercise and Sports at the University of Copenhagen, the researchers followed 330 Danish children for their first 3 years of life and analyzed stool samples collected at age 9, 18 and 36 months.
Gut bacteria composition changes significantly as breastfeeding ceases
Researchers have found merits in breastfeeding for longer; baby gut bacteria changed significantly between 9 and 18 months as breastfeeding ceased.
Using new culture-independent techniques, the team extracted DNA "signature sequences" of the gut bacteria and observed how they changed over time.
The results showed significant differences in bacteria composition between infants either breastfed or no longer breastfed at 9 months.
Plus, they also showed that the gut bacteria changed significantly between the ages of 9 months and 18 months as breastfeeding ceased and infants were weaned onto other foods. For example, there was a shift away from lactic acid bacteria.
The researchers found that the composition of the gut bacteria was "most pronouncedly influenced by the time of cessation of breastfeeding," with clear links between increase in body mass index and increase in bacteria that tend to dominate when breastfeeding ceases.
"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," they write.
Up to age 3, gut bacteria change, become more complex and stable
The results also show that the bacteria in the gut continue to change right up to the age of 3, and they become increasingly complex and more stable over this period.
Prof. Rask Licht says the findings challenge the currently held notion that gut bacteria are stable from around age 12 months:
"According to our study, important changes continue to occur right up to the age of 3. This probably means that there is a 'window' during those early years, in which intestinal bacteria are more susceptible to external factors than what is seen in adults."
She says the study lends support to initiatives that encourage the development of healthy gut bacteria in young children.
This could take the form of advice to mothers about breastfeeding and also to developers of infant formula about how to promote beneficial gut bacteria.
Meanwhile, Medical News Today recently reported on a study from the US that found breastfeeding may protect against inflammation and heart disease in young adulthood. Reporting in the journal Proceedings of the Royal Society B: Biological Sciences, the researchers warn that babies of low birth weight and those who are either never breastfed or only for up to 3 months, are more likely to have levels of chronic inflammation that can contribute to heart disease and metabolic disorders as young adults.