Fecal Short-Chain Fatty Acid Variations by Breastfeeding Status in Infants at 4 Months: Differences in Relative versus Absolute Concentrations

Abstract

Our gut microbiota provide a number of important functions, one of which is the metabolism of dietary fiber and other macronutrients that are undigested by the host. The main products of this fermentation process are short-chain fatty acids (SCFAs) and other intermediate metabolites including lactate and succinate. Production of these metabolites is dependent on diet and gut microbiota composition. There is increasing evidence for the role of SCFAs in host physiology and metabolic processes as well as chronic inflammatory conditions such as allergic disease and obesity. We aimed to investigate differences in fecal SCFAs and intermediate metabolites in 163 infants at 3-5 months of age according to breastfeeding status. Compared to no exposure to human milk at time of fecal sample collection, exclusive breastfeeding was associated with lower absolute concentrations of total SCFAs, acetate, butyrate, propionate, valerate, isobutyrate, and isovalerate, yet higher concentrations of lactate. Further, the relative proportion of acetate was higher with exclusive breastfeeding. Compared to non-breastfed infants, those exclusively breastfed were four times more likely (aOR 4.50, 95% CI 1.58-12.82) to have a higher proportion of acetate relative to other SCFAs in their gut. This association was independent of birth mode, intrapartum antibiotics, infant sex, age, recruitment site, and maternal BMI or socioeconomic status. Our study confirms that breastfeeding strongly influences the composition of fecal microbial metabolites in infancy.

Keywords: breastfeeding; gut microbiota; infants; lactate; short-chain fatty acids; succinate.

Figure 1

Mean relative proportion of short-chain fatty acid according to breastfeeding status. N = 158. Breastfeeding status at fecal sample collection.

Figure 2

Acetate fecal concentration (A) and as a relative proportion of total short-chain fatty acid (B), according to breastfeeding status at fecal sample collection. N = 158. Comparisons by non-parametric Kruskal–Wallis test (with Bonferroni posttest for multiple comparison). Box plots present the group median (thick black line), upper quartile (top of box), and lower quartile (bottom of box). Whiskers present the maximum and minimum values excluding outliers (denoted by circles).

Figure 3

Effect of infant diet on fecal short-chain fatty acids (SCFAs) and potential effect on host metabolic and immune programming. Human milk feeding causes changes in infant fecal metabolites, potentially through effects on gut microbiota composition (a). Changes in concentrations and relative proportions of SCFA and intermediate metabolites exert local effects on the gut environment and act as signaling molecules effecting host metabolism and immune system. These actions may have important programming effects on inflammatory-mediated diseases in childhood, including obesity and allergic disease (b).