Plant DNA in feces as a nutritional crystal ball

Over the last century, nutritional science uncovered that proper nutrition is a lot more nuanced than the total amount of calories a person consumes per day. This understanding permeated popular culture, as evident, for example, by the huge supplement market (>290 billion USD/year) (1). Revealing the connection between nutrition and health is the challenging realm of nutritional epidemiology, and in this issue of PNAS, Petrone et al. (2) provide strong support for the utility of a new and potentially transformative tool in the search for links between diet and health—sequencing plant DNA from stool samples.