Relationship of dietary macronutrient intake with the relative abundance of bifidobacteria and lactobacilli in breast milk of normal-weight mothers compared to the obese: a case-control study

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BACKGROUND: Lactobacillus and Bifidobacterium are members of the probiotic bacteria with many health benefits. Breast milk is an important source of these beneficial genera, which are affected by several factors. In the present study, the population of these genera was measured in milk of obese vs. normal-weight lactating women and their relationship with dietary macronutrient's intake was investigated. METHODS: Twenty women with high body mass index (BMI) enrolled as obese (≥ 30 kg/m2) and 20 women with normal BMI (18.5-24.9 kg/m2) were selected as controls. Breast milk samples were collected 4 months after delivery (due to stabilization of milk microbiome). Dietary information was collected using a food frequency questionnaire. DNA was extracted from milk. The population of Bifidobacterium and Lactobacillus was measured against 16 S rRNA gene amplification method. RESULTS: Bifidobacterium was significantly higher in breast milk of controls than the obese (p = 0.04). Bifidobacterium was 89% lower in breast milk of obese mothers than the controls, adjusting for the assessed parameters (p < 0.001). Pre-pregnancy weight showed a significant effect on the population of Bifidobacterium (p < 0.001). Energy, protein, carbohydrates, total fiber, soluble and insoluble fiber showed a positive effect on Bifidobacterium population, while dietary fat showed a negative effect (p < 0.001 in all cases). CONCLUSIONS: The breast milk population of Bifidobacterium is associated with maternal weight. Maternal dietary intake of energy, carbohydrate, protein and fibre showed a positive effect on this genus, while dietary fat showed a negative effect.