Comment on “The overlooked impact of background diet and adherence in nutrition trials” by J. I. Ottaviani, H. Schroeter, D. M. Bier, J. W. Erdman, Jr, H. D. Sesso, J. E. Manson and G. G. C. Kuhnle, Food Funct.

Inter-individual variability in gVLM _B microbial metabolism and the short-excretion kinetics of SREM _B limit biomarkers reclassification of flavanol intake in the COSMOS trial, warranting dedicated validation for intended use.