['We investigated the effect of branched-chain amino acids (BCAA) supplementation on tissue damage during distance running.', 'Eight male distance runners (mean +/- standard deviation; age: 20.4+/-1.2 years, body weight: 58.4+/-4.2 kg) participated in a double blinded cross over designed study conducted during training camp. During each intervention period, the subjects were asked to participate in a 25-km run, and the blood BCAA and lactate dehydrogenase (LDH) level, an index of tissue damage, were measured pre- and post-run. Either a drink containing BCAA (0.4% BCAA in a 4% carbohydrate solution) or an iso-calorie placebo drink was provided to the subjects 5 times during the run without any restriction in the volume.', 'The total volume of the drink consumed by the subjects did not differ substantially between the trials: 591+/-188 (2.36 g BCAA) vs 516+/-169 mL in BCAA and placebo trial, respectively. During the run, the blood BCAA concentration was maintained in the BCAA trial. However, the blood BCAA concentration level tended to decrease in the placebo trial (P<0.1). The extent of the blood LDH increase in the BCAA trial was significantly less than that of the placebo trail (48% vs 58%, P<0.05).'] Does branched-chain amino acids supplementation attenuate the accumulation of blood lactate dehydrogenase during distance running?