THE beneficial gut bacteria that a baby develops as a result of breastfeeding prepares the digestive system to take on solid foods later, according to a small study by scientists at the University of North Carolina School of Medicine.

While the benefits of breastfeeding are numerous and well known -- including the fact that they promote the colonization of healthy bacteria in the gut -- the current study suggests the transition to solid foods is less dramatic for breastfed babies.

"We think the microbiomes of non-exclusively breastfed babies could contribute to more stomach aches and colic," says senior author Dr. Andrea Azcarate-Peril, assistant professor in the department of cell biology and physiology.

Babies should be exclusively breastfed for the first six months to reap these benefits to the fullest, according to first author Dr. Amanda Thompson, an associate professor in the department of anthropology.

"We can see from the data that including formula in an infant's diet does change the gut bacteria even if you are also breastfeeding," says Dr. Thompson. "Exclusive breastfeeding seems to really smooth out the transition to solid foods."

In the study, the research team worked with nine babies from whom they collected stool samples and their health and diet history from two weeks of age through 14 months.

To find out what species of bacteria were living in the babies' bellies, the team applied genomic sequencing techniques to the stool.

In a finding consistent with past research, babies who were exclusively breastfed had different bacterial composition from those who were fed a combination of breast milk and formula.

Of notable interest was the stark contrast between stool samples of exclusively breastfed babies before and after they began eating solid food -- at which point 20 additional bacterial enzymes had taken up residence.

Meanwhile, in the babies fed a combination of breast milk and formula, 230 new enzymes had entered the scene, according to the study.

The new bacterial species help process the new foods, and the most beneficial of them for digestion is Bifidobacterium, which was found in proportionately higher numbers in the exclusively breastfed babies than in the partially breastfed babies.

"The study advances our understanding of how the gut microbiome develops early in life, which is clearly a really important time period for a person's current and future health," said Thompson.

The study was published in the journal Frontiers in Cellular and Infection Microbiology.