The effect of protein supplements on functional frailty in older persons: A systematic review and meta-analysis

The effect of protein supplementation in attenuating loss of muscle mass, strength and function in community-dwelling older people has been promising, however, its benefits in pre-frail and frail older people remains unclear.

To determine the effect of protein supplementation on muscle mass, strength and function in frail older people by reviewing and conducting meta-analysis of relevant randomized controlled trials (RCTs).

This review was registered at PROSPERO (CRD42017079276) and conducted according to Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines. Using a pre-determined e-search strategy, we searched PubMed, Medline, EMBASE, CINAHL, LILACS, Web of Science, Cochrane and Scopus databases. Inclusion criteria were RCTs that assessed the effect of protein supplementation on muscle mass, strength and function in frail individuals aged ≥65 years. The main outcomes were lean body mass (LBM), handgrip, leg extension, leg press strength, short physical performance battery (SPPB) score, and gait velocity.

Of the eight studies included in this review, 503 subjects were enrolled and four different protein supplements were assessed. Despite the variation in methodology, studies were homogenous with I-squared <10.0%. The meta-analysis showed no significant effect of protein supplementation on LBM (mean difference 1.17 kg, 95% CI: -1.97-4.3), handgrip (mean difference 0.15, 95% CI: -0.95-1.24), leg extension (mean difference -3.68 kg, 95% CI: -12.72-5.36), leg press (mean standardized difference 0.26 kg, 95% CI: -0.30-0.82), SPPB (mean difference 0.61, 95% CI: -0.02-1.23), or gait velocity (mean difference -0.20 m/s, 95% CI: -0.95-0.55).

Protein supplementation alone does not significantly improve muscle mass, strength or function in pre-frail or frail older people.