Unveiling secrets in poop: DNA barcoding reveals what we really eat

The marker they focused on is a specific region of DNA found in plants that power chloroplasts, the organelles responsible for converting sunlight into sugars. Known as trnL-P6, this genomic region is present in all plants but varies slightly from one species to another.

The team conducted a series of experiments, testing the marker on over 1,000 fecal samples from 324 participants across five different studies. Approximately twenty of the participants had high-quality records of their diets.

Their findings revealed that these DNA markers indicated the consumed foods and provided insights into the relative amounts of certain species. Moreover, the diversity of plant DNA discovered in feces varied based on a person's diet, age, and household income.

To identify the specific plant sources, the researchers relied on a reference database of dietary plants containing markers for 468 species commonly eaten by Americans. With some adjustments, their DNA barcode successfully distinguished 83% of major crop families.

Petrone noted that the crop families currently undetectable by the barcode were those predominantly consumed in other parts of the world. To enhance the technique's effectiveness, the team is working on adding crops like pearl millet and pili nuts to their database.

While the researchers haven't yet tracked meat intake using the DNA barcode, Dr. David mentioned that the technology could do so. Determining the plant-to-animal intake ratio is crucial when assessing nutritional factors.

Results from various trials.

In one experiment, the scientists applied the marker to fecal samples from individuals participating in a weight loss intervention. They were able to trace the relative amounts of wild rice, white rice, portobello mushrooms, onion, pecans, thyme, parsley, and sage

In another study involving 60 adults, the team correlated the number of plants detected by trnL with dietary diversity and quality estimated from the participants' survey responses regarding their eating habits.

Dr. David emphasized that the barcode can accurately identify the diversity of plants in a sample, serving as a proxy for dietary diversity, a recognized marker of nutrient adequacy, and improved heart health.

This technique is even more promising because it can reconstruct dietary data from past studies. The genomic analyses performed by the team were conducted on samples collected years ago, opening up possibilities for reevaluating completed studies.

The researchers believe that this new methodology will revolutionize human nutrition studies. Dr. David expressed his enthusiasm, stating, "We can use genomics to help gather data on what people eat around the world, regardless of differences in age, literacy, culture, or health status."

So, the next time you claim to have eaten your greens, your DNA may just reveal the truth lurking in your feces. With DNA barcoding, researchers are unraveling the mysteries of our diets, ultimately shedding light on various aspects of our health and history.