Diet plays a crucial role in health, yet accurately capturing what people eat remains a significant challenge for nutrition researchers. Traditional methods, such as food frequency questionnaires or 24-hour recalls, are costly, time-consuming, and prone to inaccuracies because individuals often forget or misreport their intake. This difficulty has limited the scope and scale of nutrition studies, typically confining rigorous research to small, controlled metabolic chamber settings where participants’ food consumption can be closely monitored.

A recent study published in the Proceedings of the National Academy of Sciences proposes a novel approach to gathering dietary data by analyzing sewage. By examining wastewater for traces of food DNA, researchers from North Carolina have demonstrated the potential to identify hundreds of consumed food items at a community level. This method, costing less than a penny per person, could provide detailed insights into dietary patterns across populations.

Researchers collected and preserved wastewater samples during the early months of the COVID-19 pandemic, focusing on an area covering approximately 2.1 million people—around one-fifth of North Carolina’s population. The team sequenced genetic material from plant chloroplasts and animal mitochondria present in the sewage, detecting food-related DNA fragments that survived digestion. The data revealed distinct dietary trends linked to community characteristics, such as black-eyed peas correlating with rural areas, beer ingredients aligning with more affluent neighborhoods, and tropical fruits like mango and coconut marking immigrant populations.

Despite promising results, there are limitations to wastewater-based diet analysis. Variations in DNA content among foods affect detectability; for example, leafy greens yield stronger DNA signals than starchy vegetables, while refined sugars contain minimal genetic material. Additionally, the process cannot easily distinguish between different processed forms of the same ingredient. Some researchers are exploring complementary methods, such as measuring chemical biomarkers—fiber compounds or metabolites like ethyl sulfate, which indicates alcohol consumption—to gain further insights into dietary intake and nutrient exposure.

Wastewater data are inherently noisy, influenced by factors such as degradation during transport through aging sewer systems and contamination from nonhuman waste, including animal feces and organic debris from restaurants or the environment. To mitigate these challenges, researchers processed samples promptly and excluded DNA from non-edible plants and animals to focus on human diets. Comparisons between wastewater data and individual stool samples showed consistent patterns, supporting the reliability of the approach at the community scale.

Experts emphasize that wastewater surveillance is better suited for detecting dietary trends over time rather than precise quantification of individual intake. Validation efforts akin to those used for COVID-19 genomic monitoring are ongoing to establish stronger ground truth measures.

Beyond scientific exploration, the use of sewage to monitor diet raises ethical and privacy concerns. Sampling often covers large populations at municipal treatment plants, but researchers are investigating neighborhood-level analyses while maintaining anonymity by avoiding very small populations. Community engagement has become a priority, with researchers working alongside local leaders in Durham, North Carolina, to ensure data use benefits residents. For example, members of the Hayti neighborhood—an area historically known as Black Wall Street and currently a food desert—have partnered with scientists to document local dietary gaps. This information supports efforts to attract grocery stores and improve food access, illustrating the practical implications of wastewater diet surveillance.

While wastewater analysis offers a promising new tool for public health and nutrition research, balancing scientific advancement with privacy and community interests will be critical as the field progresses.