Associations among Maternal Nutrient Intake and Infant Fecal and Human Milk Microbiomes in Exclusively Breastfeeding Samoan Mother–Infant Dyads

Human diet is changing rapidly around the world, and literature suggests that diet impacts human microbiomes. It is unclear whether maternal nutrient intake is associated with the milk and infant gastrointestinal (gut) microbiomes in nutritionally transitioning populations where wide dietary variability may uniquely shape microbial exposures and responses.

We examine how maternal nutrient intake is associated with the human milk and infant fecal microbiomes in Samoa, a nutritionally transitioning nation.

Exclusively breastfeeding Samoan mother–infant dyads (n = 100) were recruited between 2 and 4 mo postpartum across urban, peri-urban, and rural regions to capture the nutrition transition. Daily energy-adjusted maternal nutrient intake was assessed using 24-h diet recalls. Human milk and infant fecal microbiomes were characterized through 16S rRNA gene sequencing.

Total lipid (β = 0.002, P = 0.037) and saturated fatty acid intakes (β = 0.005, P = 0.020) were positively associated with evenness in milk, whereas protein intake was positively associated with richness (β = 0.232, P = 0.010) and Stenotrophomonas (β = 0.001, q = 0.022) in milk. Polyunsaturated fatty acid intake was positively associated with Shannon diversity (β = 0.034, P = 0.023), evenness (β = 0.007, P = 0.011), and Clostridium (β = 0.006, q = 6.904 × 10–5) in infant feces. Fiber intake was negatively associated with Shannon diversity (β = −0.023, P = 0.008) and evenness (β = −0.004, P = 0.023) in infant feces. Nutrient intake was not associated with overall bacterial compositions of either milk or infant feces (P > 0.05).

In Samoa, maternal nutrient intake is linked with the diversity and individual taxa of milk and infant feces, but was not associated with overall microbiome composition. Effects of changing maternal diet on maternal and infant microbiomes may therefore contribute to health outcomes associated with the nutrition transition.