Testing local wastewater came to the forefront during the COVID-19 pandemic as a tool to track viral outbreaks. Now, that same infrastructure is providing a clear look into exactly what entire communities are eating.
A newly published study has successfully demonstrated that analyzing residual plant and animal DNA in municipal wastewater can deliver accurate, real-time population nutrition data. Researchers say this breakthrough could fundamentally change how public health officials monitor dietary habits, food insecurity, and economic health.
"We have these wastewater samples that could tell you something about the nutrition of an entire community, or maybe an entire community over different seasons of the year, or a rural community versus a metropolitan community," said Dr. Rachel Noble, an environmental microbiologist at the UNC Institute of Marine Sciences in Morehead City.
Digging into the Genetic Menu
Traditionally, tracking what a population eats relies on self-reported surveys, food diaries, and grocery sales data. However, these legacy methods are expensive, slow, and highly vulnerable to human bias.
To solve that, Dr. Noble and her colleagues used a high-throughput DNA sequencing platform. By analyzing what gets flushed down the toilet, the system gathers objective dietary data for a fraction of a penny per person.
The research team tested the platform across 19 different North Carolina communities, covering a footprint of roughly two million people. Using frozen wastewater samples collected during the early days of the pandemic, scientists extracted residual plant and animal DNA that managed to survive human digestion.
The results revealed an incredibly detailed biological inventory of the regional diet, identifying genetic markers from nearly 200 plant varieties and more than 100 animal species. Dr. Noble noted that the data clearly shifted alongside seasonal harvests.
"Melons and some summertime consumption of different things that were happening in the summer," Dr. Noble explained. "Some signals that you were seeing year-round like chocolate and pistachio... Some cabbage, actually, that emerged as being more of a December or a fall winter kind of an item in this particular data set. And then things like rice and canola were showing up year-round, which those are staples that people use a lot of."
Verifying the Wastewater Mirror
To ensure the flushed DNA accurately reflected actual human consumption—and wasn't just random environmental runoff or food waste—researchers compared the sewage data against individual stool samples collected in Durham. The datasets closely aligned, confirming that municipal wastewater serves as a highly reliable mirror of a community's true diet.
But the platform tracked more than just seasonal harvests. When cross-referenced with census data, the dietary DNA profiles varied cleanly along socioeconomic lines, mapping specific lifestyle and cultural indicators across different towns.
"In more rural communities, sometimes food scarcity is such an issue that meat might not be a really prominent part of their diet," Dr. Noble said. "In a very urban or metropolitan location, you might have a lot of restaurants and there might be quite a bit of heavy meat consumption."
The data also highlighted distinct community habits:
- Economic Trends: Local financial metrics and tourism patterns strongly tracked with genetic markers from beer ingredients, like hops and barley.
- Cultural Indicators: Areas with larger foreign-born populations showed distinct spikes in tropical fruits and lentils.
- Geographic Variations: Coastal communities left behind a massive DNA signature of local seafood consumption that was entirely unique to the coast.
"It's basically a replication of what you see in the grocery store and in the fish markets of eastern North Carolina," Dr. Noble said regarding the coastal data. "You don't see Spanish mackerel in Charlotte. It doesn't travel well, right? You don't see red drum in Charlotte in a grocery store... There's not a lot of triggerfish that gets caught in North Carolina. I can tell you from my personal experience that if it is caught in eastern North Carolina, it's going to get eaten in eastern North Carolina because it's delicious."
In contrast, inland communities relied much more heavily on commercial, farmed fish like Atlantic salmon.
Policy and Economic Impacts
Dr. Noble points out that this technology offers a scalable, real-time solution for monitoring nutrition and identifying food deserts, all while fully protecting individual privacy. Beyond health, the data could also be used to bolster the eastern North Carolina commercial fishing industry.
"Apparently lots of species of seafood that you can see that we uncover that are Atlantic fish species that are being consumed in Beaufort and we can track them in the sewage of Beaufort, but they're not getting eaten in a lot of other parts of the state," Dr. Noble said. "How do we improve that? Is it a fisherman limitation? Is it a cost problem?"
She noted that while the federal government heavily subsidizes the pork and beef industries to keep grocery store prices attractive, local fishermen do not receive similar safety nets.
Ultimately, researchers hope this data can be used by state leaders to improve public health policies and ensure vulnerable communities have better access to affordable, nutritious foods.
"We fairly well know that beans and legumes are an important part of many longevity diets," Dr. Noble said. "Are there ways that we can improve the access or the ability for all people in North Carolina to become more educated on those products... instructing families on how you can make them in ways that are healthy but also appealing to everyone."
