Breastfeeding from birth to six months is the gold standard of feeding as it dramatically reduces the risk of infectious and allergic diseases, in part because human milk oligosaccharides promote the growth of a beneficial microbiota. Although there are a number of circumstances which necessitate infants to receive supplemental formula.
Perhaps the most unique characteristic of the intestinal microbiota among exclusively breastfed infants, as compared to formula-fed infants, is increased abundance of bifidobacteria.
Bifidobacterium longum subspecies (subsp.) longum, Bifidobacterium longum subsp. infantis, and Bifidobacterium breve have been strongly associated with beneficial health outcomes, including preventing enteric inflammation, reducing diarrhea, and improving allergy symptoms.
A recent study showed a correlation between bifidobacteria abundance in early infancy and CD4+ T-cell responses to immunisations. But studies so far have not had access to detailed data on dietary intake, which might influence both intestinal microbiota and immune responses.
The current prospective, longitudinal study of 24 healthy infants was carried out to determine the relationship between dietary intake, intestinal microbiota, and immune development.
The study found that differences in infant microbiotas were largely determined by delivery methods and not formula supplementation, with delivery method effecting observed microbiota until as late as six months of age.
Supplementation caused transient changes in the microbiota, notably increases in Campylobacter, Dermabacter, Peptoniphilus, Prevotella, and S24-7; and a decrease in Eggerthella. However, these differences diminished by the age of six months.
No differences were detected in the immune development of supplemented vs. unsupplemented infants, whether in immunophenotypes or responses to the tetanus vaccine.
The researchers conclude that early supplementation to support infant nutrition when breast milk supply is inadequate had no detectable detrimental effects on microbiome diversity or immune function.
Infants were recruited from the University of California San Francisco (UCSF) Medical Center. Dietary intake data were collected at birth; 1 week; and 1, 3, and 6 months of age. Data on receipt of immunisations were collected at one, three, and six months of age.
Approximately equal sample sizes were available for infants receiving or not receiving supplementation by one month of age (n = 11 and n = 13, respectively).
Stool specimens were collected with Stool Nucleic Acid Collection and Preservation Tubes (Norgen Biotek Corp., Thorold, ON, Canada) at birth; 1 week; and 1, 3, and 6 months. Meconium was collected on the day of birth. In total, 105 samples were successfully sequenced (using microbial 16S rRNA gene sequencing) at an average of 87,000 (10,491–1,537,440) reads per sample.
Blood specimens for the assessment of immune function were collected by heel stick at birth and at 1, 3, and 6 months of age.
PBMCs were successfully extracted from 65 blood samples and analyzed using flow cytometry. Frequencies of monocytes and T-cell subsets in peripheral blood samples were determined by flow cytometry of cryopreserved PBMCs.
The main limitations are the small sample size, the small amount of blood collected from infants, and sporadic data on type of formula used for supplementation.
Flaherman. V. J., et al
"Transient Effect of Infant Formula Supplementation on the Intestinal Microbiota"