Associations of Plastic Bottle Exposure with Infant Fecal Microbiota, Short-Chain Fatty Acids, and Growth.

Background: Plastic exposures have been shown to impact the microbiome, metabolism and growth of animals. However, no human studies have examined how plastic exposures are associated with fecal microbiota, microbial metabolites, or growth. Here we examine the association of plastic bottle feeding with infant fecal microbiota, microbial short-chain fatty acid (SCFA) metabolites, and anthropometry in the first year of life. Methods: 462 infants from the prospective Nurture Birth Cohort were included to examine frequency of plastic bottle feeding (every feeding vs. less than every feeding) at 3 months with anthropometric outcomes (skinfolds, length-for-age, and weight-for-length) at 1 year. A subset of 64 and 67 infants were included in analyses examining the fecal microbiota and fecal SCFAs, respectively. Microbial taxa were measured by 16S rRNA gene sequencing of the V4 region and SCFA concentrations were quantified using gas chromatography at 3 and 12 months of age. Results: After adjustment for potential confounders, less frequent plastic bottle use was associated with lower fecal microbiota alpha Shannon diversity at 3 months (mean difference for plastic bottle used less than every feeding vs. every feeding = -0.53, 95% CI: -0.90, -0.17, p < 0.01) and lower propionic acid concentration at 3 months (mean log + 1 difference for plastic bottle used every feeding vs. less than every feeding = -0.53, 95% CI: -1.00, -0.06, p = 0.03). Furthermore, compared to infants who used plastic bottle at every feeding, infants who were plastic bottle-fed less frequently (1 -3 times/day) at 3 months had significantly lower length-for-age z-scores at 12 months (mean difference= -0.40, 95% CI: -0.72, -0.07, p = 0.016). Conclusion: Plastic bottle exposure may impact early infant gut microbiota and microbial SCFAs, which may in turn affect growth.