Table 4.

Effects of protein supplementation on changes in lower‐body strength

Groups/subgroups	SMD	95% CI	Number of trials/intervention groups	P‐value	I 2 (%)
All RCT reporting lower‐body strength	0.20	0.08:0.33	50/70	<0.01	52.8
RCT without resistance exercise	0.14	−0.36:0.64	4/4	0.44	20.4
RCT with resistance exercise (RE)	0.21	0.08:0.34	47/66	<0.01	54.5
<65 years old	0.19	0.03:0.36	35/52	0.02	52.8
≥65 years old	0.25	0.01:0.48	12/14	0.04	60.6
RCT with RE reporting protein ingestion	0.21	0.08:0.34	41/56	<0.01	49.5
Ingesting <1.2 g/kg/day	−0.01	−1.85:1.83	2/2	0.95	0
Ingesting 1.2–1.59 g/kg/day	0.08	−0.10:0.27	20/28	0.37	51.6
Ingesting ≥1.6 g/kg/day	0.40	0.23:0.57	19/26	<0.01	26.1
<65 years old	0.38	0.19:0.56	17/24	<0.01	62
≥65 years old	0.55	0.04:1.06	2/2	0.03	0
Meta regression – protein ingestion as a continuous variable (g/kg BW/day) in all RCT reporting protein ingestion	0.25	0.05:0.45	44/60	0.016	NA
Meta regression – protein ingestion as a continuous variable (g/kg BW/day) in studies using RE	0.26	0.05:0.47	41/56	0.014	NA

BW, body weight; CI, confidence intervals; NA, not applicable; RCT, randomized clinical trials; RE, resistance exercise; SMD, standardized mean deviation.