(Poly)phenol profiles of plant-based diets assessed through dietary intake and urinary biomarkers

(Poly)phenols are bioactive compounds widely present in plant-based foods. The aim was to explore differences in (poly)phenols based on dietary intake and urinary measurements among omnivores and different types of plant-based diets (PBDs). A total of 792 participants completed a 175-item food frequency questionnaire; 200 (51% PBD followers) provided first-morning urine samples. The Phenol-Explorer database was used to estimate dietary (poly)phenol intake. Food contributions to total (poly)phenols and a (Poly)Phenol-rich diet Score (PPS) were assessed. Urinary total (poly)phenols and concentrations of 28 (poly)phenols were quantified using liquid chromatography-tandem mass spectrometry. Diet groups were compared using the Kruskal-Wallis test. Principal component analysis and Spearman's correlation were performed to explore associations between dietary and urinary (poly)phenols. Total and individual (poly)phenol intakes were higher for PBDs compared to omnivores. Among vegans, vegetables (20.8%) and fruits (10.4%) were the main contributors to total (poly)phenols; this pattern was reversed in the other groups. Significant differences (p < 0.001) were also observed in the contribution of other plant-based foods, resulting in distinctive profiles across diet groups. PBDs scored higher in the PPS and showed the highest intake and urinary values of isoflavonoids (e.g., vegans: 94 mg per 2000 kcal per day and 1424 ng mL^-1, respectively). Genistein and daidzein levels were strongly correlated with their intake values (rho ∼ 0.6), as well as with legumes and soy-rich foods. A cluster driven by urinary isoflavonoids was identified. Both dietary and urinary (poly)phenols predominated in PBDs. Genistein and daidzein represent stable biomarkers of legume and soy intake and are key indicators of plant-based dietary patterns.