What goes down household drains may seem like waste, but scientists have discovered it can reveal valuable information about the foods people eat.
A new study suggests that community wastewater can provide a quick and surprisingly accurate picture of local diets.
Understanding what people eat is important because diet affects the risk of heart disease, diabetes, obesity, and many other long-term illnesses. Until now, researchers have mainly relied on food surveys and diaries, but these methods are not always accurate because people may forget what they ate or choose not to report unhealthy foods.
Scientists from Duke University School of Medicine and the University of North Carolina at Chapel Hill tested a very different approach.
Instead of asking people questions, they examined tiny pieces of plant and animal DNA that end up in community wastewater after food is prepared, eaten, and digested. This allowed them to study eating habits without identifying any individual person.
The team collected wastewater samples from 19 communities across North Carolina representing about 2.1 million residents. Using a DNA sequencing system called FoodSeq-FLOW, they identified traces of many different foods and compared the results with information about local populations, income levels, and geography.
The researchers found clear differences between communities. Wealthier neighborhoods were more likely to contain DNA from hops, an important ingredient used to make beer.
Communities with larger immigrant populations showed more evidence of tropical fruits and beans, while coastal areas contained more DNA from seafood such as drum, Spanish mackerel, and triggerfish.
To check whether the method was reliable, the scientists compared wastewater results with DNA found in stool samples collected in Durham. The patterns closely matched, suggesting that wastewater can provide a realistic picture of what people are eating across an entire community.
The researchers believe this approach could become a valuable public health tool. It may help governments understand whether healthy food is reaching different neighborhoods, identify areas with limited food choices, and measure whether food assistance programs are working as intended.
The method also protects privacy because it measures large groups rather than individuals. No personal information is collected, and the results only describe overall community eating patterns. This allows researchers to study nutrition while respecting people’s privacy.
The scientists say the technology could also support local planning. For example, communities trying to attract grocery stores or improve access to fresh food may be able to use this information to demonstrate local needs and measure whether changes improve diets over time.
The study was led by researchers from Duke University School of Medicine and the University of North Carolina at Chapel Hill and published in the Proceedings of the National Academy of Sciences. The findings show that wastewater may become an important new source of nutrition information.
Although the approach cannot measure exactly what each person eats, it offers a fast, objective way to study eating habits across large populations. As the technology improves, it could help shape nutrition policies, food security programs, and public health planning while protecting individual privacy.
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