Effects of γ-aminobutyric acid (GABA) intake in combination with exercise on muscle strength in humans with decreased mobility: a randomized, double-blind, placebo-controlled, parallel-group study

Background: Aging-related declines in skeletal muscle mass, muscle strength, and physical function are related to instability, falls, and frailty in older people, resulting in the need for nursing care. Objective: To investigate the effect of oral γ-aminobutyric acid (GABA) intake and exercise on muscle parameters in healthy subjects whose muscle strength is beginning to decline with age. Methods: A randomized, double-blind, placebo-controlled, parallel-group comparative study was conducted. Fifty subjects (over 40 years old) were randomly divided into the GABA (100 mg/day) or placebo food intake group. Subjects orally consumed the respective study substance every day for 12 weeks. They performed daily “locomotion training” as devised by the Japanese Orthopedic Society. Muscle mass, fat mass, and knee extension muscle strength were measured. Results: The two groups had no significant differences in muscle and fat mass. Compared with the placebo food group, the GABA group showed a significant improvement in knee extension muscle strength in the left and right legs at pre-dose Week 0 (at Week 6, p = 0.02). In post hoc subgroup analysis by sex, when compared with the placebo food intake group, the GABA food intake group showed significant improvement in knee extension muscle strength of the right leg at Weeks 6 (p = 0.001) and 12 (p = 0.007), the left leg at Week 6 (p = 0.02), the stronger of the left and right legs at pre-dose Week 0 (at Week 6, p = 0.001), and the weaker of the left and right legs at pre-dose Week 0 (at Week 12, p = 0.013) in males. Conclusions: These results suggest that GABA intake combined with daily exercise is effective for maintaining knee extension muscle strength, which decreases with age. Furthermore, there were no safety issues with the intake of GABA-containing food during this study. Trial registration: UMIN-CTR: UMIN000050152. Keywords: γ-Aminobutyric acid, GABA, Muscle mass, Knee extension muscle strength, Aging