Short-chain fatty acid (SCFA) and medium-chain fatty acid (MCFA) concentrations in human milk consumed by infants born at different gestational ages and the variations in concentration per lactation stage

This study aimed to quantify the short-chain fatty acids (SCFAs) and medium-chain fatty acids (MCFAs) in human milk and investigate their concentrations in human milk consumed during lactation by infants born at different gestational ages. One hundred eighty milk samples from mothers of 30 full-term, 10 early-preterm (≤32 wk), 10 mild-preterm (32–34 wk), and 10 near-term (34–37 wk) infants were collected from colostrum, transitional, and mature milk. The human milk triacylglycerols (TAGs) were transferred into fatty-acid methyl esters via potassium methoxide in methanol and determined using gas chromatography (GC). Total SCFA (4:0) and MCFA concentrations (6:0 and 8:0) were highest in the mature milk (1.47 ± 0.66 mg/g fat from full-term infant milk) and were approximately 42.18% higher than those in transitional milk. Significantly higher SCFA and MCFA concentrations were found in full-term milk than in preterm milk (p = 0.001). The milk TAGs were analyzed using ultra-high-performance supercritical fluid chromatography with quadrupole-time-of-flight mass spectrometry (UHPSFC-Q-TOF-MS), which showed that the SCFAs and MCFAs were mainly esterified with long-chain fatty-acid groups (16:0, 18:1 n-9, and 18:2 n-6) at the glycerol backbone. The infants’ daily SCFA intake from human milk was estimated. The infants’ daily SCFA were highest in from mature milk for full-term infants (~14 mg/d) which significant different from preterm infants intaked from colostrum and transitional milk (p < 0.001). The correlation between dietary SCFAs and MCFAs in human milk and nutrition in newborns, especially in the gut microbiotas of preterm infants, requires further study.