Using DNA barcoding, researchers have developed a means of teasing out what people have eaten from their stool samples, a tool that could aid nutritional studies. As they report in the Proceedings of the National Academy of Sciences, researchers from Duke University and elsewhere applied a metabarcoding approach relying on the chloroplast trnL-P6 marker to determine what plant species were present in more than 1,000 fecal samples from individuals from five different dietary studies. The number of plant taxa the barcoding approach identified in the samples largely correlated with what the study participants reported eating. The researchers further report that, with their reference database, they could distinguish 83 percent of the major crop families, suggesting their barcodes could be used as objective dietary markers. "We are limited in how we can track our diets, or participate in nutrition research or improve our own health, because of the current techniques by which diet is tracked," senior author Lawrence David from the Duke Microbiome Center says in a statement. "Now 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." The researchers additionally note that the diversity of plant DNA found among participants’ stool samples varied not only by diet but also age and household income.