DNA metabarcoding captures dietary plant diversity in individuals and cohorts

Eating a varied diet is a central tenet of good nutrition. Here, we develop the first molecular tool to quantify human dietary plant diversity by applying DNA metabarcoding with the chloroplast trnL -P6 marker to 1,001 fecal samples from 310 participants across four cohorts. The number of plant taxa per sample (plant metabarcoding richness, or pMR) correlated with recorded intakes in interventional diets (ρ=0.31) and with indices calculated from a food-frequency questionnaire in freely-chosen diets (ρ=0.40-0.63). In adolescents unable to collect validated dietary survey data, trnL metabarcoding detected 111 plant taxa, with 86 consumed by more than one individual and four (wheat, chocolate, corn, and potato family) consumed by >70% of individuals. Adolescent pMR was associated with age and income, replicating prior epidemiologic findings. Overall, trnL metabarcoding promises an objective and accurate measure of the number and types of plants consumed that is applicable to diverse human populations.