TABLE 3.

Effect of whey protein supplementation on changes in muscle strength

Groups/subgroups	Effect size (SMD)	95% CI	No. of interventions/outcomes	I2 (%)	P-heterogeneity	P between-subgroup heterogeneity
All RCTs	0.149	−0.086, 0.383	32	83.81	0.214
RCT conducted on healthy older adults	0.178	−0.097, 0.454	21	82.29	<0.001	0.250
RCT conducted on sarcopenic/frail older adults	0.085	−0.375, 0.546	11	87.13	<0.001
RCT measuring upper body strength	0.079	−0.336, 0.494	11	86.97	<0.001	0.671
RCT measuring lower body strength	0.189	−0.104, 0.482	21	82.48	<0.001
RCT with RE	0.238	0.001, 0.474	21	70.99	<0.001	0.296
RCT without RE	−0.052	−0.540, 0.436	11	91.56	<0.001
RCT with high dose of whey (>20 g/d)	0.252	0.051, 0.453	25	69.66	<0.001	0.141
RCT with low dose of whey (<20 g/d)	−0.349	−1.123, 0.426	7	94.12	<0.001
RCT with high duration (>12 wk)	0.079	-0.230, 0.388	20	87.39	<0.001	0.472
RCT with low duration (≤12 wk)	0.253	-0.105, 0.610	12	72.97	<0.001

Abbreviations: RCT, randomized controlled trial; RE, resistance exercise; SMD, standardized mean difference.