What do people eat? Plant and animal DNA in sewage provide clues

Key takeaways

Analyzing DNA in sewage offers a promising new method to understand community dietary habits more comprehensively than traditional surveys.
A wide variety of foods, including plants, herbs, spices, and animal species, can be detected in sewage DNA samples, though some closely related plants are harder to distinguish.
DNA can survive through digestion and sewage environments, allowing for retrospective analysis of diets from historic samples.
Sampling is feasible with small quantities of sewage, and ethical considerations are addressed by ensuring anonymity and community transparency.
This research has applications in assessing food accessibility, tracking dietary trends, and potentially informing public health initiatives.

Summary

Introduction to Sewage DNA Analysis for Dietary Insights

Flora Lichtman introduces Dr. Lawrence David and his innovative research project called The Edible Atlas, which analyzes genetic material found in sewage to determine community dietary habits. This method offers a potentially more comprehensive view of what people eat compared to traditional surveys or grocery sales data.

What Foods Are Detectable in Sewage?

Dr. David explains the range of foods that show up in sewage samples, including common staples like rice, bananas, wheat, and soybeans, as well as herbs and spices such as rosemary, sage, garlic, and ginger. He notes the ability to identify different species of animals, like fish, and discusses the limitations in distinguishing closely related plants due to genetic similarities.

DNA Preservation and Analysis in Sewage

The discussion covers the resilience of DNA through digestion and its survival in sewage, with estimates that about 99% of DNA from food is digested. Despite this, millions of copies of DNA from everyday food consumption remain detectable in sewage, allowing researchers to analyze community diets even from historic samples.

Methodology for Sampling Sewage DNA

Sampling involves collecting sewage either directly from wastewater treatment plants or by open access, with permission. Small quantities, like liters or even teaspoons, can suffice. The process includes using absorbent materials to capture DNA, which is then sequenced to identify different plant and animal sources.

Applications and Ethical Considerations of Sewage DNA Data

This approach could revolutionize understanding of food access and consumption at the community level, providing rapid data to inform nutritional interventions. Privacy concerns are addressed by sampling areas with at least 500 people to ensure anonymity, and community engagement is prioritized to address ethical questions.

Personal Inspiration and the Path to the Research

Dr. David shares his background, including collecting his own feces for a microbiome study, which laid the groundwork for his current research. His first-hand experience with the persistence of DNA in feces and sewage inspired this novel application, combining microbiology and genomics to study human diets indirectly.

Show notes

Imagine you wanted to get a general idea of what people are eating in a given community. You could look at grocery store sales, or do surveys, but neither can capture a complete picture.

Microbiome researcher Lawrence David and his lab look to another source of data: genetic material in sewage water. It turns out that detectable DNA signatures of individual plant and animal species remain behind even after they’ve been eaten, digested, excreted, and flushed down the toilet. He joins Host Flora Lichtman to describe his “Edible Atlas” project, the backend limitations of sewage analysis, and where the research might go.

Guest:

Dr. Lawrence David is an associate professor of molecular genetics and microbiology in the Center for Genomics and Computational Biology. He runs the Edible Atlas project at Duke University.

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The transcript for this episode is available at sciencefriday.com.

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