Formula feeding tied to changes in infant gut microbiome composition

Last Updated: 2016-01-12

By Anne Harding

NEW YORK (Reuters Health) - Babies fed a mix of breast milk and formula have gut microbiome compositions similar to those of babies fed formula only, according to new findings.

And the microbiota of babies fed any formula are significantly different in composition from those of exclusively breastfed infants, Dr. Juliette Madan and Dr. Anne Hoen of the Geisel School of Medicine at Dartmouth College in Hanover, New Hampshire, and their colleagues found. They reported their findings online January 11 in JAMA Pediatrics.

"We had expected to find the opposite, so this is somewhat surprising," Dr. Madan told Reuters Health in a telephone interview.

There is growing evidence for an association between gut microbiome composition and many key health outcomes in adults, the authors note, but relatively little research has been done on the gut microbiome in infants and children. Previous research has linked delivery method and exposure to breastfeeding to intestinal microbiome profiles in babies, they add. Exposure to vaginal microflora during delivery may be important in establishing an infant's own microbiome, while breast milk may foster its development.

In the new study, the investigators used next-generation sequencing of the 16S rRNA gene to compare the intestinal microbiome compositions of 102 healthy six-week-old infants. Seventy infants were delivered vaginally, and 32 by cesarean section. Seventy of the babies were exclusively breastfed, 26 received breast milk and formula, and six were given formula only.

Both delivery mode and feeding method were independently associated with gut microbiome composition as characterized by UniFrac analysis. There were statistically significant differences in microbiome composition between exclusively breastfed infants and infants fed on formula only, as well as between the infants breastfed exclusively and those who received both breast milk and formula. However, there was no statistically significant difference in microbiome composition between the formula-only and mixed-feeding groups.

The differences between vaginally delivered babies and babies delivered by C-section were similar to the differences among the different feeding groups.

The vaginally born infants had an increased abundance of Bacteroides, which is a known component of healthy infant gut microbiota and is important for immune-system maturation, Dr Hoen told Reuters Health in a telephone interview.

"As we follow this cohort as they age and as we collect data about health benefits and health risks, we will be able to better clarify if there are health effects associated with the patterns that we're seeing," Dr. Madan said. She and her colleagues plan to follow the children up to five years of age.

The ultimate goal of this research, according to Dr. Madan, will be to find interventions to restore healthy microbiomes in infants whose microbiomes have been altered by certain exposures.

"It's a good study, it's not surprising to me," Dr. Meghan Azad of the Children's Hospital Research Institute of Manitoba in Winnipeg told Reuters Health in a telephone interview. Dr. Azad studies the infant microbiome, but did not take part in the new research. She noted that giving an infant even a small amount of formula is providing the gut bacteria with new food that could potentially alter bacterial populations in the intestine.

It's important for doctors and parents to understand the potential effect of both mode of delivery and infant feeding now and in the future, she added.

"These are important decisions that likely have long-term implications for health in ways we hadn't appreciated before this microbiome research was going on," Dr. Azad said. "It's a tricky subject because we don't want to be blaming or shaming moms for their decisions, but at the same time we want the information to be out there to help inform their choices."

The National Institutes of Health and the Environmental Protection Agency supported this research. The authors reported no disclosures.

SOURCE: http://bit.ly/22WSJ4t

JAMA Pediatr 2016.