URINARY 3-METHYLHISTIDINE EXCRETION - ASSOCIATION WITH TOTAL-BODY SKELETAL-MUSCLE MASS BY COMPUTERIZED AXIAL-TOMOGRAPHY

Background: The urinary excretion of endogenous 3-methylhistidine (3-M H) has been proposed as a predictor of skeletal muscle mass (SM). In t his study, we report the relationship between 24-hour urinary 3-MH exc retion and SM. Methods: Total body SM was measured by multiscan comput erized axial tomography (CT) in a sample of 10 healthy adult men who f ollowed a meat-free diet for 7 days. 3-MH was measured during the last 3 days of the meat-free diet protocol on consecutive 24-hour urine co llections, Results: The 3-MH excretion was 216.3 +/- 44.7 mu mol/d (me an +/- SD) and was found well associated with SM (in kilograms), SM = 0.0857 x 3-MH +/- 11.8; r = .88, P < .001, Compared with CT, the previ ous 3-MH-SM prediction equation suggested by Lukaski et al underestima ted SM by an average of 8.9 kg in the 10 healthy men, This difference was caused by the Burkinshaw-Cohn neutron activation model, which unde restimated SM and was used as the reference in the Lukaski method. Con clusions: Twenty-four-hour urinary 3-MH excretion can be applied for e stimating SM in healthy adult men on a meat-free diet.