D3‐Creatine dilution for body composition assessment: A direct take on the matter

D3-Cr is simple, safe, precise and of minimal subject burden including for neonates and bedridden/clinical populations; it is also practical for remote assessments. 1,3 Furthermore, SMM estimated from D3-Cr is associated with physical performance, incidence of falls, fractures and mobility limitations in older adults. 4,5 Notwithstanding the important positive aspects of the D3-Cr method, it is not without limitations, which were addressed in a comprehensive review by McCarthy et al. 1 In this paper, the authors credit the decades of historical developments that led to the current use and understanding of the D3-Cr method and consider its physiological premises. [...]they provide an intriguing and compelling discussion on methodological assumptions and therefore setbacks of the technique. 1 These include considerations regarding the validity of the D3-Cr method, and the actual body composition compartment measured, with both topics interpreted considering modern evidence from skeletal muscle research. D3-Cr estimates SMM from creatine pool size, which in turn is impacted by physiological premises of D3-Cr absorption, distribution, catabolism and excretion. 1 McCarthy et al. 1 further highlight that SMM creatine concentration is not constant and varies between muscles and muscle composition, age, disease states and dietary patterns.