RESUMO
OBJECTIVES: In preterm infants, the metabolic responses of gastrointestinal (GI) bacteria to different diets are poorly understood despite the possible effects on GI health. Therefore, we tested the hypothesis that diet influences bacterial metabolism by measuring short-chain fatty acids (SCFAs) in stool samples from very-low-birth-weight (VLBW) preterm infants without GI disorder as surrogate biomarkers of bacterial metabolism. METHODS: Ion chromatography was used to measure fecal SCFAs (acetate, formate, propionate, butyrate, and isobutyrate), lactate, and chloride in fresh stool samples collected from 32 preterm infants (without major congenital anomalies, GI disorders, or a recent history of antibiotic administration and on full feed of either expressed maternal breast milk [EBM; n = 13] or a formula for preterm infants [Similac Special Care Formula; preterm formula, PTF; n = 19]). RESULTS: The mean birth weight was 972 g, the mean gestational age was 27 weeks, and the mean postnatal age at first stool sample was 36 days. When adjusted for gestational age, the stools of EBM infants had higher concentrations (micromoles per gram of stool) of total SCFA (128 vs 68; P = 0.002), acetate (41 vs 13; P = 0.005), propionate (15.1 vs 4.4; P = 0.003), and chloride (21,814 vs 10,652; P = 0.02). Interactions between postnatal age and diet were detected for lactate (P = 0.05), propionate (P = 0.03), and butyrate (P = 0.03). CONCLUSIONS: Diets fed to VLBW preterm infants influence fecal SCFA profiles, and hence the metabolism of the GI bacteria, and potentially the health of preterm infants. The responses of bacterial metabolism to diet are influenced with postnatal age and gestational age at birth.