Integrated multiomic wastewater-based epidemiology can elucidate population-level dietary behaviour and inform public health nutrition assessments.

Population-level nutritional assessments often rely on self-reported data, which increases the risk of recall bias. Here, we demonstrate that wastewater-based epidemiology can be used for near real-time population dietary assessments. Neighbourhood-level, untreated wastewater samples were collected monthly from within an urban population in the south-western United States from August 2017 to July 2019. Using liquid chromatography-tandem mass spectrometry, we identify recurring seasonal dynamics in phytoestrogen consumption, including dietary changes linked to the winter holiday season. Using 16S ribosomal RNA gene amplicon sequencing, we demonstrated the feasibility of detecting sewage-derived human gut bacterial taxa involved in phytoestrogen metabolism, including Bifidobacterium, Blautia and Romboutsia. Combined metabolomic and genomic wastewater analysis can inform nutritional assessments at population scale, indicating wastewater-based epidemiology as a promising tool for actionable and cost-effective data collection to support public health nutrition.