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.
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