Supplementary Material for: Total and Sn-2 Fatty Acid Profile in Human Colostrum and Mature Breast Milk of Women Living in Inland and Coastal Areas of China

Introduction: Although lipid is the major energy source and exerts beneficial effects on infant growth, research on the composition of fatty acid (FA) at the sn-2 position of human milk (HM) in China and abroad is limited. Objectives: This study aimed to investigate the FA positional distribution in colostrum and mature HM of women living in the inland and coastal areas of China and explore the potential influences of geographical region and lactation stage on the FA profile of Chinese women. Methods: Colostrum milk (n = 61) and mature milk (n = 56) samples were obtained longitudinally from healthy lactating women in Guangzhou and Chengdu, China. Gas chromatography was used to determine the total and sn-2 FA composition. Results: Significant differences were observed in the FA profile of HM between different regions and lactation stages, with differences in polyunsaturated FA levels being the most pronounced. Nearly 70% of sn-2 FAs were saturated FAs, of which C16:0 accounted for approximately 75%. C8:0, C10:0, C18:0, C20:0, C22:0, and all of the unsaturated FAs were mainly located at the sn-1 and sn-3 positions, while C14:0, C15:0, and C16:0 were mainly at the sn-2 position. The proportion of C12:0 and C17:0 at sn-2 was approximately equivalent to that at the sn-1, 3 positions. Conclusions: The results indicate the variability in the FA profile of HM between regions and lactation stages. The contents of polyunsaturated FAs and sn-2 FAs, especially palmitic acid, should be paid more attention when optimizing infant formula.