Environmental toxicants in breast milk of Norwegian mothers and gut bacteria composition and metabolites in their infants at 1 monthOriginal paper
Karen Pendergrass is a microbiome researcher specializing in microbiome-targeted interventions (MBTIs). She systematically analyzes scientific literature to identify microbial patterns, develop hypotheses, and validate interventions. As the founder of the Microbiome Signatures Database, she bridges microbiome research with clinical practice. In 2012, based on her own investigative research, she became the first documented case of FMT for Celiac Disease, four years before the first published case study.
Read MoreWhat was studied?
This birth cohort study asked whether environmental toxicants in breast milk affect the infant gut microbiome and its function at 1 month of age. Researchers measured 28 chemicals in breast milk. The chemicals included polychlorinated biphenyls, brominated flame retardants, per- and polyfluoroalkyl substances, and organochlorine pesticides. Infant stool was profiled by 16S ribosomal RNA gene sequencing (V4 region). Fecal short-chain fatty acids were measured, and elastic net regression modeled exposure links to diversity and metabolites.
Who was studied?
The cohort was 267 mother-child pairs from the Norwegian Microbiota Cohort. Infant gut microbiota and breast milk chemical levels were both characterized at about 1 month postpartum. Mothers averaged 30.4 years old, were 99.6% Caucasian, and mostly non-smokers. Preterm deliveries were oversampled at 22.5%. Short-chain fatty acid analysis was limited to a subset of 70 infants. Toxicants were detected in over 96% of milk samples.
What were the most important findings?
PBDE-28 and PFOS were linked to less microbiome diversity. One standard deviation more PBDE-28 meant 4% less Shannon diversity; PFOS meant 5% less phylogenetic diversity. Highly exposed infants had lower abundance of sub-OTUs of an important early-life Firmicutes genus. Toxicants explained up to 34% of variance in propionic acid. PBDE-28 was tied to 24% less propionic acid and PCB-209 to 15% less acetic acid. Conversely, PFOA raised propionic acid 61% and dioxin-like PCB-167 raised acetic acid 22%.
What are the greatest implications of this study?
The findings suggest breast milk toxicants may influence infant gut microbial function during a key developmental window. This points to a previously overlooked mode of action for persistent pollutants. Effects were inconsistent across chemicals and metrics, and the toxicant links were smaller than those from preterm birth or formula feeding. The authors urge caution. Because the design is observational, causation is not established. Whether these microbiome shifts affect child health remains unknown and needs replication in other populations.