Protein supplementation improves muscle mass and physical performance in undernourished prefrail and frail elderly subjects: a randomized, double-blind, placebo-controlled trial

Background: Age-related loss of muscle mass and function is a major component of frailty. Nutrition supplementation with exercise is an effective strategy to decrease frailty by preventing sarcopenia, but the effect of protein alone is controversial. Objective: The present study was performed to investigate a dose-dependent effect of protein supplementation on muscle mass and frailty in prefrail or frail malnourished elderly people. Design: A 12-wk double-blind randomized controlled trial was conducted in elderly subjects aged 70-85 y with >= 1 of the Cardiovascular Health Study frailty criteria and a Mini Nutritional Assessment score <= 23.5 (n = 120). Participants were randomly assigned to 1 of 3 groups: 0.8, 1.2, or 1.5 g protein . kg(-1) . d(-1), with concealed allocation and intention-to-treat analysis. Primary outcomes were appendicular skeletal muscle mass (ASM) and skeletal muscle mass index (SMI) measured by dual-energy X-ray absorptiometry. Results: After the 12-wk intervention, the 1.5-g protein . kg(-1) . d(-1) group had higher ASM (mean +/- SD: 0.52 +/- 0.64 compared with 0.08 +/- 0.68 kg, P = 0.036) and SMI (ASM/weight: 0.87% +/- 0.69% compared with 0.15% +/- 0.89%, P = 0.039; ASM/BMI: 0.02 +/- 0.03 compared with 0.00 +/- 0.04, P = 0.033; ASM: fat ratio: 0.04 +/- 0.11 compared with -0.02 +/- 0.10, P = 0.025) than the 0.8-g protein . kg(-1) . d(-1) group. In addition, gait speed was improved in the 1.5-g protein . kg(-1) . d(-1) group compared with the 0.8-g protein . kg(-1) . d(-1) group (0.09 +/- 0.07 compared with 0.04 +/- 0.07 m/s, P = 0.039). There were no significant differences between the 1.2- and 0.8-g protein . kg(-1) . d(-1) groups in muscle mass and physical performance. No harmful adverse effects were observed. Conclusions: The present study indicates that protein intake of 1.5 g . kg(-1) . d(-1) has the most beneficial effects in regard to preventing sarcopenia and frailty compared with protein intakes of 0.8 and 1.2 g . kg(-1) . d(-1) in prefrail or frail elderly subjects at risk of malnutrition.