A new study suggests what's flushed down the drain can offer a real-time snapshot of what communities are eating.
Researchers at Duke University School of Medicine and the University of North Carolina at Chapel Hill analyzed tiny fragments of plant and animal DNA from wastewater samples across 19 North Carolina communities representing 2.1 million people to reveal how economics, immigration, and geography influence what's on our plates.
Wealthier neighborhoods was more likely to show traces of hops, a key ingredient in beer. Areas with larger foreign-born populations revealed evidence of tropical fruit and bean consumption. Along the coast, wastewater carried signatures of seafood-rich diets, including locally caught species like drum, Spanish mackerel, and trigger fish.
Published in the Proceedings of the National Academy of Sciences , the study turns an unlikely source — community sewer systems — into a data-rich tool to help track nutrition trends, identify gaps in food access, and determine whether food security programs are reaching the people who need them most.
"Poor diet is one of the world's biggest drivers of chronic disease, but we've never had a fast objective way to measure what people eat," said senior study author Lawrence A. David, PhD , a member of the Duke Microbiome Center and an associate professor of molecular, genetics and microbiology whose research lab is known as the Edible Atlas . "This study helps fill that gap so we can better connect diet to health."
For decades, nutrition researchers relied on food diaries and surveys for nutrition surveillance — methods that can be expensive and time-consuming. People forget what they ate, underreport unhealthy foods, or are never surveyed at all. The communities most affected by diet-related disease are often the hardest to measure, David said.
To address those limitations, Duke researchers developed FoodSeq-FLOW, a DNA-sequencing platform that mines traces found in wastewater for clues about what communities are eating and preparing.
While at Duke, lead study author Mengyi Dong, PhD , spearheaded the genomic analysis and translated the DNA sequences into identifiable plant and animal species.
The approach builds on wastewater surveillance systems that took off during COVID-19 when virus shed in human waste helped officials detect and track outbreaks. Now it's used to monitor a variety of infectious and respiratory diseases.
But researchers are pushing the infrastructure beyond disease detection. Using the new sequencing platform, the team analyzed wastewater samples collected from eight treatment plants in three North Carolina regions — Charlotte-Mecklenburg; Beaufort-Carteret and Greenville-Pitt — during two study periods June-December 2020 and June 2021.
"Wastewater offers an objective way to monitor dietary patterns across entire communities and could help guide more targeted nutrition and food security programs," said Dong, an associate professor at Virginia Tech's Seafood Agricultural Research and Extension Center. "Food security isn't just about whether enough food is available. It's also about ensuring communities can access healthy, nutritious options."
The potential is attracting interest from communities such as Durham's historic Hayti neighborhood where local leaders are working to bring in a Black-owned full-service grocery store.
They believe this data could help demonstrate the measurable impact a grocery store could have in the area that's been described as a food desert.
"It would allow us to eat healthier foods more regularly because we wouldn't have to travel so far to get them," said Erin Dooley, co-founder of BLK South and resident of the Grant Street Community . "What's unique about Dr. David's research is that it's not just hard facts and data, but it supports our lived experiences."
The DNA patterns found in wastewater closely matched dietary data from 14 stool samples collected in Durham in June 2021, suggesting that sewage can accurately track local diets.
Researchers emphasize that the goal though is not to monitor individuals but to measure broad community patterns.
By capturing information from entire populations without identifying specific people, wastewater could fill critical gaps in public health data while protecting privacy, said study author Rachel T. Noble, PhD , a professor of marine sciences at UNC-Chapel Hill.
"The result is a snapshot of the community that helps understand where resources are needed," Noble said.
Noble notes that the DNA markers developed at Duke can identify food sources with remarkable detail. For instance, diets among inland communities rely on a handful of seafood varieties, especially farmed fish such as Atlantic salmon.
"Could we be doing more to support local fisheries and make their seafood more available? It looks like we certainly could," Noble said.
Additional authors include Thomas Clerkin; Sharon Jiang; Nolan Ives; Olivia W. Osborne; Michelle Kirtley; Anne E. Bauer; Katherine Anderson; and Martin D. Smith.
Funding for the study was provided by the National Science Foundation; Chan Zuckerberg Initiative; Schmidt Sciences; the Gerber Foundation; Nature-Springer; Burroughs Wellcome Fund Pathogenesis of Infectious Disease Award; Duke Microbiome Center, Duke Clinical and Translational Science Award; and the National Institute of Diabetes and Digestive and Kidney Diseases.
