Effects of supplemental protein in older people: an overview of meta-analyses

Abstract

Background: Benefits of supplemental protein in older people in different health states and settings are uncertain. This review aimed to determine the effects of supplemental protein on health outcomes in older people.

Methods: An overview of reviews. Cochrane Library, MEDLINE (Ovid), EMBASE (Ovid), Cumulative Index to Nursing and Allied Health Literature (CINAHL) (EBSCOhost) and Google Scholar were searched from January 1990 to August 2024. Systematic reviews with meta-analyses reporting protein intake's effect on health outcomes were included. Methodological quality was assessed using the Assessing Methodological Quality of Systematic Reviews 2 critical appraisal tool. Inconsistency between results from different reviews was explored by examining effects by population type [healthy people, living with long-term conditions (LTCs), hospital inpatients] and whether supplementation was given with or without concomitant exercise.

Results: Thirty-three reviews with meta-analyses collating data from 441 unique studies were included. There was no increase in muscle mass, strength or physical performance from protein supplementation in older people in general, nor in healthy older people. There was medium-certainty evidence of at least small increases in muscle mass and strength in older people with LTCs, and the benefits of protein supplementation were more certain with concomitant exercise. Evidence suggests that protein supplementation in hospital patients with hip fractures reduced the number of medical complications.

Conclusion: Protein supplementation is effective for improving muscle mass and strength in older people with LTCs and medical complications in older hospitalised patients with hip fractures. The evidence does not support its routine use in other groups of healthy older people.

Keywords: community-dwelling; hospitalised; malnutrition; older adults; protein supplementation; systematic review.

Figure 1

PRISMA diagram. n, number; nRCTs, non-randomised control trials.

Figure 2

Forest plot of review results for the effect of protein supplementation upon muscle mass, presented by participant type and whether protein supplementation was given in the presence of concomitant exercise. ALM, appendicular lean mass; ASM, appendicular skeletal muscle mass; ASMI, appendicular skeletal muscle mass index; LBM, Lean body mass; CSA, cross-sectional area; FFM, fat-free mass; LBM, lean body mass; MM, muscle mass; MoM, mixture of measures; PUL&LL MM&V, Pooled upper limb and lower limb muscle mass and volume.

Figure 3

Forest plot of review results for the effect of protein supplementation upon muscle strength, presented by participant type and whether protein supplementation was given in the presence of concomitant exercise. CU&LLM, combined upper and lower limb measures; HGS, handgrip strength; KES, knee extensor strength; LBS, lower body strength; LES, lower extremity strength; LLS, lower limb strength; LPS, leg press strength; LS, leg strength; MIS, maximal isometric strength; MS, muscle strength; OLL, operated lower limb; ULL, unoperated lower limb; UBS, upper body strength.

Figure 4

Forest plot of review results for the effect of protein supplementation upon physical performance, presented by participant type and whether protein supplementation was given in the presence of concomitant exercise. CAPO, composite of all performance outcomes; CM, combined measures; CRT, chair rise test; GS, gait speed; LTCs, long-term conditions; OPT, other physical test; SC, stair climbing; SPPB, short physical performance battery; TUGT, timed up & go test; WC, walking capacity; WS, walking speed.