Diets high in fiber and fat have been shown to alter the microbiota residing in the adult human gastrointestinal tract.  This begs an important question; can mothers’ diets influence the microbial composition of human milk?

Few studies have examined the association between maternal diet and the milk microbiota.  Furthermore, previous studies have focused solely on metabolically healthy participants. Thus, it remains unclear whether the relationship between maternal diet and the milk microbiota differs in women with metabolic dysfunction, which is known to influence the microbiota composition in the gastrointestinal tract.

A study published in The Journal of Nutrition investigated whether maternal diet and infant feeding practices are associated with milk microbiota at 3 mo postpartum in a cohort of 93 women with varying degrees of gestational glucose intolerance. Utilizing data from a previously conducted prospective cohort study, Deborah O’Connor (University of Toronto) and colleagues collected demographic and anthropometric information from women during their last trimester of pregnancy. 

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Women also underwent a 3-h glucose tolerance test to determine glucose tolerance status. A diagnosis of gestational diabetes, impaired glucose tolerance, or normal blood glucose was made based on test results. Dietary intake was collected using a food frequency questionnaire from delivery to 3 mo postpartum.  A total of 117 women donated a milk sample at 3 mo postpartum at which time mothers were asked if infants were receiving exclusive human milk, how many times the infant was fed at the breast per day versus pumped milk in a bottle, and if the infant received formula, noting both frequency and quantity per day.

Study results indicate that maternal diet and infant feeding practices are associated with the human milk microbiota at 3 mo postpartum in women with varying degrees of gestational intolerance.  This large cohort of mothers with high rates of gestational glucose intolerance demonstrated that dietary factors, including maternal consumption of fat and fiber, and infant feeding practices, such as human milk exclusivity and frequency of direct breastfeeding, were important determinants of the human milk microbiota. Given the potential for microbiota in human milk to colonize the infant’s GI tract, future research is needed to explore the implications of these findings on infant microbial colonization and health. A corresponding editorial by Michelle McGuire and Mark McGuire (University of Idaho) provides an important historical perspective pertaining to advancements in molecular techniques that have opened new avenues to better understand the microbial composition of human milk and its ability to provide health benefits to individual mothers and infants.

Reference

LeMay-Nedjelski L, Asbury MR, Butcher J, Ley SH, Hanley AJ, Kiss A, Unger S, Copeland JK, Wang PW, Stinzi A, O’Connor DL. Maternal Diet and Infant Feeding Practices Are Associated with Variation in the Human Milk Microbiota at 3 Months Postpartum in a Cohort of Women with High Rates of Gestational Glucose Intolerance. The Journal of Nutrition, Volume 151, Issue 2, February 2021, Pages 320–329, https://doi.org/10.1093/jn/nxaa248.

McGuire MK, McGuire MA. Mapping the Human Milk Microbiome: Impetus for a Long-Awaited Renaissance in Maternal and Infant Nutrition Research? The Journal of Nutrition. The Journal of Nutrition, Volume 151, Issue 2, February 2021, Pages 278–280, https://doi.org/10.1093/jn/nxaa373.

Images via canva.com.