Effect of amino acid supplementation on muscle mass, strength and physical function in elderly.
Level 4 - case-series / case-control
Uncontrolled single-arm pre-post intervention study
PubMed 18294740 · doi:10.1016/j.clnu.2008.01.001
What was done
Twelve glucose-intolerant elderly individuals (mean age 67.0 ± 5.6 years; 7 women, 5 men) consumed 11 g of essential amino acids plus arginine twice daily between meals for 16 weeks without other dietary or physical activity modifications. Lean body mass (LBM) was assessed via DEXA every 4 weeks. Maximal leg strength (one-repetition maximum for knee flexors and extensors) and functional performance (gait speed, timed 5-step test, timed floor-transfer test) were evaluated at baseline and weeks 8, 12, and 16.
What was found
Lean body mass increased significantly across the study period (p = 0.038). Compared to baseline, the average LBM gain was 1.14 ± 0.36 kg at week 12 (p < 0.05) and 0.60 ± 0.38 kg at week 16 (not statistically significant). Lower extremity strength (n = 10) increased from a baseline of 127.5 ± 21.8 kg by an average of 22.2 ± 6.1% during the study (p < 0.001). Significant improvements were also observed in usual gait speed (p = 0.002), timed 5-step test (p = 0.007), and timed floor-transfer test (p = 0.022).
Why it matters
The findings suggest that oral essential amino acid supplementation can stimulate muscle accretion and functional recovery in older adults even in the absence of structured exercise.
Limits
The study was a small, uncontrolled single-arm trial (n = 12, with only 10 participants completing strength testing), making it impossible to rule out placebo effects, test-retest learning effects, or confounding lifestyle variations. Lean mass gains attenuated by week 16 compared to week 12. The cohort was restricted to glucose-intolerant elderly individuals, which may limit generalizability.
Cited by
- partial Older women who add essential amino acids daily without altering their exercise or diet gain two to three pounds of muscle within about three months.