Urine Metabolomics during a Legume Diet Intervention Suggests Altered Metabolic Signatures and Potential New Intake Markers: First Insights

Given the general increase in legume consumption worldwide, there is a need to characterize the resulting human metabolic adaptations in order to demonstrate potential legume diet/health relationships. A nuclear magnetic resonance (NMR) metabolomics urine study was carried out on a small cohort (<i>n</i> = 18) to characterize the excretory effects of a pilot longitudinal 8-week legume-based dietary intervention. Despite the expected high interindividual variability in the excreted metabolome, the results suggested a nonlinear metabolic response, with higher metabolic activity in the first 4 weeks and a tendency toward baseline at the end of the intervention. The excretion of isoleucine, leucine, and threonine increased, along with metabolite changes suggestive of activation of the tricarboxylic acid cycle (through anaplerosis), ketogenesis, fat catabolism, and glycoprotein biosynthesis. Gut microbiota adaptations were also suggested based on the increased excretion of 2-hydroxyisobutyrate, allantoin, and hippurate. Increased levels of trigonelline were consistent with its role as a legume intake marker, whereas malonate and pseudouridine were suggested as possible additional markers. Correlation of NMR data with nutritional parameters aided putative explanatory hypotheses to be advanced. Our results suggest a dynamic response to legume consumption, mainly through increased amino acid excretion and altered energy metabolism, while advancing potential new markers of legume intake. These results require confirmation in larger cohorts but pave the way for an informed interpretation of the effects of legume-based diets on human health.