Changes in HMO Concentrations throughout Lactation: Influencing Factors, Health Effects and Opportunities

Abstract

Human milk oligosaccharides (HMOs) are important functional biomolecules in human breast milk. Understanding the factors influencing differences in HMO composition and changes in their concentration over lactation can help to design feeding strategies that are well-adapted to infant’s needs. This review summarises the total and individual concentration of HMOs from data published from 1999 to 2019. Studies show that the HMO concentrations are highest in colostrum (average 9–22 g/L), followed by slightly lower concentrations in transitional milk (average 8–19 g/L), with a gradual decline in mature milk as lactation progresses, from 6–15 g/L in breast milk collected within one month of birth, to 4–6 g/L after 6 months. Significant differences in HMO composition have been described between countries. Different HMOs were shown to be predominant over the course of lactation, e.g., 3-fucosyllactose increased over lactation, whereas 2′-fucosyllactose decreased. Recent clinical studies on infant formula supplemented with 2′-fucosyllactose in combination with other oligosaccharides showed its limited beneficial effect on infant health.

Dynamic Changes in Human Milk Oligosaccharides in Chinese Population: A Systematic Review and Meta-Analysis

“…Despite no significance, other neutral fucosylated HMOs such as LNFP I and LNFP V decreased during the course of lactation, which is in accordance with findings reported in previous studies [ 3 , 11 , 35 ]. LNnT and LNT, neutral non-fucosylated HMOs, declined throughout the lactation, and the changes reached the significant level.…”

“…2′-FL is the most abundant HMO whose biological significance includes modulating immune functions, nourishing gut prebiotics, and providing fucose moieties for the glycosylation of biomolecules such as proteins and lipids [ 1 ]. Although not significantly, the concentration of 2′-FL declined gradually along with the lactation course, which is consistent with almost all studies [ 11 , 35 ]. 3′-FL is another neutral fucosylated HMO.…”

“…Beyond 120 days, the concentrations of 6′-SL were comparable to those of 3′-SL. In line with our findings, it was proposed that 6′-SL occupies the main position among sialylated HMOs at early stages of lactation (<3 months), and the concentration of 3′-SL is higher at 4–8 months [ 3 , 35 , 37 ].…”

“…This result is in accordance with the overall dynamic changes in total concentration of all HMOs along the lactation period. Although it is not possible to measure all the HMOs in human milk, it has been reported that the total level of HMOs in colostrum is estimated to be the highest at 9–22 g/L and declines slightly in transitional milk (8–19g/L at postnatal 8–15 days), followed by a gradual decrease in mature milk [ 35 ]. However, it is worth noting that the total content of 14 HMOs showed a sharp increase in the 61–120 postnatal days, which is likely attributed to the dramatic rise in the concentration of DSLNT.…”

“…In our study, although 2′-FL and 3′-FL concentrations displayed opposite trends, the sum of 2′-FL and 3′-FL remained constant after the first week of lactation. In another study, researchers reviewed the HMO concentration among populations from different countries and observed an increasing trend of 3′-FL and a negative correlation between the production of 2′-FL and 3′-FL [ 35 ]. These observations implied the possibility that 3′-FL may compensate for 2′-FL in human milk from non-secretor mothers whose 2′-FL is dramatically lower than that from secretor mothers.…”