Effects of Branched-Chain Amino Acids on Skeletal Muscle, Glycemic Control, and Neuropsychological Performance in Elderly Persons with Type 2 Diabetes Mellitus: An Exploratory Randomized Controlled Trial

Exploratory randomized controlled trial in older adults with type 2 diabetes mellitus receiving outpatient care and participating in a structured exercise program. The study compared BCAA supplementation with isocaloric soy protein over 24 weeks in a Japanese cohort from University of Tsukuba Hospital.

Oral branched-chain amino acids were given at 8 g/day for 24 weeks as DeliciOUS Amino Acids BCAA, providing 4 g leucine, 2 g valine, and 2 g isoleucine per dose, taken after exercise or after dinner if no exercise. The active comparator was isocaloric soy protein, 7.5 g per dose for 24 weeks, also taken after exercise or after dinner if no exercise.

Neither BCAA nor soy protein improved skeletal muscle mass or HbA1c over 24 weeks, so BCAA was not superior to soy protein for the main efficacy outcomes. Both supplements increased knee extension strength, with a significant gain in the soy protein group and a trend toward improvement in the BCAA group. Depressive symptoms improved significantly in the BCAA group, although the between-group difference was not significant. LDL-C decreased in the soy protein group, and there were no significant changes in IGF-1, follistatin, or BDNF. The interventions were generally tolerated, with no major renal safety concerns.

This was an exploratory study with a small sample and limited power for secondary outcomes and safety. The 24-week duration and concurrent exercise program make supplement-specific effects harder to isolate, and the findings come from a single Japanese center in older adults with type 2 diabetes, limiting generalizability. Per-protocol analysis and some attrition further weaken certainty.