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66: Maternal diet alters the breast milk microbiome and microbial gene content

      Objective

      Breast milk contains a diverse microbiome that is presumed to colonize the infant gastrointestinal tract and contribute to the establishment of the infant gut microbiome. The composition of the breast milk microbiome varies substantially over time and among individuals, though the factors driving this variation are largely unknown. As the maternal gut microbiome is affected by diet and is a proposed source of the bacteria in breast milk, we aimed to determine the effect of maternal diet on the composition of the breast milk microbiome. We employed a multiple armed, cross-over dietary intervention study to do so.

      Study Design

      Two cohorts of lactating women participated in single-blinded cross-over studies. In the first study, lactating women (n=7) received 60% of their daily caloric intake from either glucose or galactose, with a 1 week washout period. In the second study, lactating women (n=7) consumed either a high fat diet (HFD; 55% fat, 30% carbohydrate, 15% protein) or high carbohydrate diet (25% fat, 60% carbohydrate, 15% protein), with a 1-2 week washout period. Milk samples were collected after completion of each dietary treatment. DNA was extracted from the milk and subjected to rigorous metagenomic analysis.

      Results

      The inferred functional capacity of the breast milk microbiome varied significantly by maternal diet. The galactose diet resulted in an increase in the relative abundance of genes involved in metabolism, signaling, and motility compared to the glucose diet (p < 0.05; Figure 1). Similarly, notable differences in taxonomic and metagenomic bacterial composition were observed between the high carbohydrate and HFD (Figure 2).

      Conclusion

      Maternal diet affects the inferred functional capacity of the breast milk microbiome. Variation of the resultant microbial gene community aligned with the metabolism of the diet consumed. Specifically consumption of galactose increases the abundance of bacterial genes involved in metabolism, signaling, and motility. We speculate that the maternal diet thereby serves as a significant driver of the early infant microbiome, reinforcing the gestational dietary impact.
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