Effect of β-hydroxy-β-methylbutyrate (HMB) on lean body mass during 10 days of bed rest in older adults
Background: Loss of muscle mass due to prolonged bed rest decreases functional capacity and increases hospital morbidity and mortality in older adults. Objective: To determine if HMB, a leucine metabolite, is capable of attenuating muscle decline in healthy older adults during complete bed rest. Design: A randomized, controlled, double-blinded, parallel-group design study was carried out in 24 healthy (SPPB≥9) older adult subjects (20 women, 4 men), confined to complete bed rest for ten days, followed by resistance training rehabilitation for eight weeks. Subjects in the experimental group were treated with HMB (calcium salt, 1.5g twice daily - total 3g/day). Control subjects were treated with an inactive placebo powder. Treatments were provided starting 5 days prior to bed rest till the end rehabilitation phase. DXA was used to measure body composition. Results: Nineteen eligible older adults (BMI: 21-33; age: 60-76year) were evaluable at the end of the bed rest period (Control n=8; Ca-HMB n=11). Bed rest caused a significant decrease in total lean body mass (LBM) (2.05±0.66kg; p=0.02, paired t-test) in the Control group. With the exclusion of one subject, treatment with HMB prevented the decline in LBM over bed rest -0.17±0.19kg; p=0.23, paired t-test). There was a statistically significant difference between treatment groups for change in LBM over bed rest (p=0.02, ANOVA). Sub-analysis on female subjects (Control=7, HMB=8) also revealed a significant difference in change in LBM over bed rest between treatment groups (p=0.04, ANOVA). However, differences in function parameters could not be observed, probably due to the sample size of the study. Conclusions: In healthy older adults, HMB supplementation preserves muscle mass during 10 days of bed rest. These results need to be confirmed in a larger trial.This trial is registered at http://ClinicalTrials.gov under NCT00945581. © 2013 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism.