The term “oligosaccharide” (derived from the Greek olígos, meaning little or few, and sákkhar, meaning sugar) is generally used to describe a group of complex carbohydrates made of 3 to 6 simple sugars, such as glucose and fructose. Interestingly, breastmilk contains a diverse and unique set of oligosaccharides – collectively referred to as human milk oligosaccharides (HMO). HMO profiles and amounts differ among women living in different regions of the world. For instance, whereasalmost all women living in Peru produce milk that contains the HMO 2’-fucosyllactose (2’FL), only about 70% of Ghanaian women do. Although some of this variationdue to genetics, other factors might also be important. For instance, environmental pathogen exposure might support variation in HMO profiles to best protect infants from diseases they are most at risk of contracting. There is also evidence that variation in HMO profiles are related to those of bacterial profiles found inherently in human milk.

This relationship between HMO and the milk microbes might have important implications for establishment of the breastfed infant’s gastrointestinal tract microbes. Concentration of certain HMO have also been linked to variation in the amount and profiles of maternally-derived immune cells in milk. However, nothing is known about whether HMO variation drives that of immune cells, vice verse, or the possibility that this relationship is coincidental and due to a confounding factor. To fill this knowledge gap, relationships between HMO and milk immune cells will need to be repeatedly measured and evaluated over time. Maternal diet might also impact HMO. For instance, some research suggests that concentrations of certain fatty acids found in milk (mostly derived from the diet) are correlated with both total and individual HMO concentrations.

An example is a reported inverse association between higher levels of stearic acid and lower 2’FL concentration. Foods rich in stearic acid include beef, dairy products, and tropical foods such as coconuts. However, controlled dietary intervention studies are needed to determine if these associations are causal or coincidental. In addition, longitudinal studies are needed to evaluate whether variation in HMO profiles seen across populations are related to health and wellbeing, and if so whether the relationships depend on the environment in which infants live. In summary, there are convincing data that HMO vary globally and their concentrations are related to other milk components. However, substantial research is needed to understand the importance (if any) of this variation and these relationships.

Supporting literature

Aakko J, Kumar H, Rautava S, Wise A, Autran C, Bode L, Isolauri E, Salminen S. Human milk oligosaccharide categories define the microbiota composition in human  colostrum.  Benef  Microbes. 2017;8:563-67.

Erney RM, Malone WT, Skelding MB, Marcon AA, KlemanLeyer KM, O’Ryan ML, Ruiz-Palacios G, Hilty MD, Pickering LK, Prieto PA. Variability of human milk neutral oligosaccharides in a diverse population. J Pediatr Gastroenterol Nutr. 2000;30:181–92.

Hunt KM, Preuss J, Nissan C, Davlin CA, Williams JE, Shafii B, Richardson AD, McGuire MK, Bode L, McGuire MA. Human milk oligosaccharides promote the growth  of  staphylococci.  Appl  Environ  Microbiol. 2012;78(14):4763-70.

McGuire MK, Meehan CL, McGuire MA, Williams JE, Foster J, Sellen DW, Kamau-Mbuthia EW, Kamundia EW, Mbugua S, Moore SE, Prentice AM, Kvist LJ, Otoo GE, Brooker SL, Price WJ, Shafii B, Placek C, Lackey KA, Robertson B, Manzano S, Ruíz L, Rodríguez JM, Pareja RG, Bode L. What’s normal? Oligosaccharide concentrations and profiles in milk produced by healthy women vary geographically. Am J Clin Nutr. 2017;105:1086-1100.

Williams JE, Price WJ, Shafii B, Yahvah KM, Bode L, McGuire MA, McGuire MK. Relationships among microbial communities, maternal cells, oligosaccharides, and macronutrients in human milk. J Hum Lact. 2017;33:540-51.