A key limitation in nutrition research is that current methods available for dietary assessment, including food frequency questionnaires (FFQs), food diaries or dietary recalls, are known to be error-prone and inaccurate, as they rely on self-report assessment which are subject to bias. In recent years, extensive efforts have been made to develop more reliable dietary assessment techniques, in particular, biomarkers of food intake as a more objective method to monitor dietary exposure.  Our group has developed targeted metabolomics methods for the quantitative assessment of (poly)phenol intake in human biofluids using LC-MS, and is currently working on the development of dietary scores, dietary patterns and novel dietary assessment methods for the estimation of phytochemical intake and adherence to plant-based diets.