Maternal Pre-Pregnancy Body Mass Index and Its Impact on Short- and Long-Chain Fatty Acid and Microbiome Profiles of Human Breast Milk in Caucasian Women of Northeast Tennessee

Background: Increasing evidence suggests that breast milk and its bioactive components, including short-chain fatty acids and the milk microbiome, are influenced by maternal nutrition and body mass index (BMI). Bioactive components transferred to the infant through breast milk play a pivotal role in infant growth and development and have indications in the child’s future short- and long-term health outcomes. This study aimed to assess the impact of maternal pre-pregnancy BMI (PP-BMI) on human breast milk macronutrient composition, short- and long-chain fatty acid profiles, and breast milk microbiome profiles. Approach: This was an exploratory cohort study of forty-four lactating Caucasian women, two to fourteen weeks postpartum, divided into groups based on pre-pregnancy body mass index (BMI). Study participants signed informed consent, completed health and nutritional surveys, and provided a breast milk sample. Breast milk samples were subjected to proximate analysis, microbiome identification and short- and long-chain fatty acid extraction and analysis. Results: Maternal age, maternal physical activity, infant birth weight, and time of lactation at sample collection were not significantly different between the maternal PP-BMI groups. PP-BMI was significantly different between the two maternal groups. No significant differences were found between the maternal BMI groups concerning nutritional intake. No differences in breast milk microbiomes were observed in alpha diversity and beta diversity between the maternal PP-BMI groups. For long-chain fatty analysis in breast milk samples, myristic acid was significantly higher in the PP-BMI overweight/obese group while stearic acid was significantly higher in the PP-BMI normal-weight group. Butyric, valeric, and isocaproic acid concentrations in HBM were significantly higher in the PP-BMI normal-weight group and lower or undetectable in the PP-BMI overweight/obese group. Conclusions: Data from this exploratory cohort study indicate that maternal diet and pre-pregnancy BMI may be associated with differences in selected HBM fatty acids. There were no significant differences in microbiomes for alpha and beta diversity in breast milk between maternal PP-BMI groups; however, lower relative abundance was observed in the breast milk of the PP-BMI overweight/obese group. These findings should be interpreted in the context of the study’s limitations, including convenience recruitment from a Facebook group, the modest sample size, and restriction to Caucasian women from a single geographic region.