Gut Microbiome Similar in Formula- and Combination-Fed Babies

Troy Brown, RN

January 13, 2016

The intestinal microbiome in 6-week-old infants was the same in babies who were exclusively formula fed and babies who were fed with both formula and breast milk, according to a new study. Babies who were exclusively breast-fed had an intestinal microbiome that was distinctly different from those who were fed only formula or a combination of formula and breast milk. However, mode of delivery appeared to be a more important factor in microbiome development than feeding practices.

Juliette C. Madan, MD, from the Division of Neonatology, Department of Pediatrics, Children’s Hospital at Dartmouth, Lebanon, and the Children’s Environmental Health and Disease Prevention Research Center at Dartmouth, Hanover, New Hampshire, and coauthors report their findings in an article published online January 11 in JAMA Pediatrics.

"To our knowledge, our study was the first to examine the contribution of delivery mode to infant intestinal microbiome composition in association with that of another important predictor of microbiome composition, infant diet," the researchers write. "We found that delivery mode was more strongly associated with infant microbiome composition than was diet at 6 weeks."

The researchers reviewed the medical records of 102 infants who were followed up as part of the New Hampshire Birth Cohort Study to determine delivery mode and ascertained feeding information from telephone questionnaires. They analyzed the infants' stool samples at 6 weeks for microbiome composition and determined associations among birth type, feeding method, and intestinal microbiome.

The average gestational age of the infants was close to 40 weeks; 70 newborns were delivered vaginally, and 32 underwent cesarean delivery.

During the first 6 weeks of life, 70 infants were breast-fed exclusively, 26 were fed with both breast milk and formula, and six were fed only formula.

After adjustment for the effects of feeding type, the mode of delivery was strongly associated with the babies' gut microbiome composition (P < .001; Q < .001).

After adjustment for the effects of delivery method, the association between feeding type and the infants' gut microbiome composition was also statistically significant (P = .01; Q < .001).

Pairwise comparisons of the three feeding methods showed that babies who were exclusively breast-fed had an intestinal microbiome community that was distinct from that of babies who were either exclusively formula fed (P = .04; Q = .05) or those who were both breast-fed and formula fed (P = .02; Q = .04). The researchers found no statistically significant difference in the intestinal microbiome between babies fed both breast milk and formula and those who were fed exclusively formula.

However, further analysis suggested that the microbial differences seen with different delivery methods were greater than seen with different feeding practices.

"Understanding the patterns of microbial colonization of the intestinal tract of healthy infants is critical for determining the health effects of specific alterable early-life risk factors and exposures," the authors conclude. "To this end, we have identified measurable differences in microbial communities in the intestinal tracts of infants according to their delivery mode and diet, with possible consequences for both short- and long-term health."

The authors have reported no relevant financial relationships.

JAMA Pediatr. Published online January 11, 2016. Full text

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