Scientists have discovered an unexpected way to monitor what entire communities are eating: by analyzing DNA in municipal wastewater. Researchers at Duke University and the University of North Carolina at Chapel Hill developed a method called FoodSeqFLOW that sequences plant and animal DNA from wastewater treatment plants to reveal population-level dietary patterns in real time. The approach costs less than one cent per person and could help public health officials detect nutritional changes and respond more rapidly to emerging health concerns.

How Does Wastewater Sampling Reveal What People Eat?

The research team collected 183 wastewater samples from 21 North Carolina municipalities, representing 2.1 million people. They sequenced genes for plant chloroplasts and animal mitochondria, which are the energy-producing structures in plant and animal cells, to identify dietary information. The method works because food passes through the human digestive system and leaves genetic traces in sewage. By analyzing these traces, researchers can determine which foods communities are consuming without relying on individual surveys, which often suffer from recall bias, low response rates, and high costs.

To validate their approach, the researchers compared plant profiles from two community sampling sites in Durham, North Carolina to those of 14 individuals from the city. They found highly similar dietary profiles between the community-level and individual samples, confirming that wastewater analysis accurately reflects what people actually eat. Most of the plant and animal sequences detected in wastewater samples mapped to foods consumed by humans, reducing the likelihood of environmental contamination skewing the results.

What Do Dietary Patterns Reveal About Socioeconomic Status and Geography?

The findings uncovered striking connections between what people eat and where they live. Using statistical analysis, researchers evaluated whether FoodSeqFLOW could detect geographic and socioeconomic differences in dietary patterns. The results showed clear disparities based on income and location:

• Urban and Affluent Areas: Plant-based diets were more common in affluent, urban centers, with greater diversity of food types overall.
• Rural Communities: Samples from rural and less populated areas had higher representation of traditional Southern American cuisine, including potatoes, celery, onion, black-eyed peas, and black pepper.
• Socioeconomic Correlation: The richness and diversity of food taxa positively correlated with socioeconomic status and the size of Asian and foreign-born populations, while food insecurity negatively correlated with food diversity.

The researchers also observed regional differences in seafood consumption. Rural and coastal communities had greater representation of local fish species, while inland and urban areas had sequences corresponding to nationally distributed seafood species. Interestingly, the team detected plant sequences not associated with foods consumed for nutrition, including craft beer ingredients and kratom, an herbal substance legal in North Carolina. These signatures correlated with high-income populations and could serve as unique biomarkers for discretionary income.

How Can Communities Use This Information to Improve Public Health?

The ability to detect real-time dietary patterns offers public health officials a powerful new tool for monitoring and responding to nutritional changes at the population level. Unlike traditional methods that rely on surveys or national sales data, wastewater sampling provides affordable, rapid insights into what communities actually consume. The researchers also investigated whether FoodSeqFLOW could detect temporal variations in community diets by collecting samples from different treatment plants across three cities between June and December, then again the following June. They found that food profiles shifted in response to seasonal availability of vegetables and fruits, demonstrating the method's ability to track dietary changes over time.

According to the study authors, these findings suggest that wastewater surveillance offers a reliable, cost-effective option to study dietary patterns and inform public health policy. However, the researchers noted important limitations, such as the inability to sample people with septic systems, which are common in rural areas. Despite these constraints, the method represents a significant advance in understanding community nutrition at scale.

Why Does Global Diet Matter for the Planet and Public Health?

Beyond tracking what communities eat, research shows that shifting toward healthier diets could have profound implications for both human health and environmental sustainability. A new modeling study published in Nature examined what could happen if the world pursued a food system transformation similar to recommendations from the 2025 EAT-Lancet Commission. The analysis, conducted by researchers from the London School of Hygiene and Tropical Medicine, Cornell University, and 10 modeling teams, found that a worldwide transition to healthy diets could prevent 15 million premature deaths every year.

The modeling also revealed dramatic environmental benefits. If the world shifted toward healthier diets, agriculture-related net carbon dioxide emissions from land-use change could be 85% lower by 2050 compared with 2020 levels. Land-use change includes activities such as clearing forests, converting grasslands, or draining wetlands to create agricultural land, which releases large amounts of stored carbon into the atmosphere. The transformation would also reduce global farmland use by as much as 6% compared with current trends.

The biggest changes would occur in livestock production. The global value of ruminant animal production, which includes beef cattle, sheep, and goats, could decline by an estimated 70% by 2050, with roughly 400 million fewer ruminant animals worldwide than in 2020. Meanwhile, plant-based food production would expand dramatically. The combined global value of vegetables, fruits, nuts, and legumes could rise by 57%, or approximately 890 billion dollars. Legumes, which include beans, peas, lentils, and chickpeas, are important sources of protein and fiber and generally require fewer resources to produce than many animal foods.

"Transforming food systems would deliver enormous potential benefits to our health and the environment but, as our results make clear, they would also lead to fundamental changes to global agriculture and affect the lives of millions of farmers and food producers," said Dr. Matt Gibson, lead author of the study.

Dr. Matt Gibson, Lead Author, London School of Hygiene and Tropical Medicine

The economic effects of such a transformation would vary substantially between countries and regions. In the United States, the total value of agricultural production could fall by 21% by 2050 compared with 2020, though crop production value could increase by 20% while livestock production value could decline by 73%. India could experience a very different outcome, with total agricultural production value rising by 46%, driven by a 65% increase in crop production value. Europe could see its overall agricultural production value decline by 35%, with livestock production falling by 66%.

The researchers emphasized that their scenarios represent only a selection of many possible futures and assume a costless shift in consumer preferences toward healthy diets. In reality, healthy foods may not be equally affordable or accessible everywhere, and dietary choices are shaped by local traditions, personal preferences, income, food availability, and cultural attitudes. Bold policy decisions made now could help protect vulnerable food producers and consumers as agriculture moves toward healthier and more sustainable diets.