Table 1.

Randomized controlled trials of protein supplementation and sarcopenia.

Author	Population	Intervention	Results of Supplemental Protein vs. Placebo	With Exercise?
Björkman 2010 [15]	n = 218, age 75–96 years, either low hand-grip strength (men ≤ 30.0 kg, women ≤ 20.0 kg), slow habitual gait speed (≤0.80 m/s), or cRi-SMI Z-score ≤ −2.	Nutritional supplement: enriched milk protein (40 g). Groups: supplement group vs. isocaloric placebo for 12 months.	Nonsignificant differential impact on physical performance or attenuation of muscle loss.	Yes, participants given a training program for 12 months.
Tieland 2012 [16]	n = 62, age ≥ 65 years, met Fried criteria for either frailty or pre-frailty.	Nutritional supplement: 15 g protein beverage supplemented by milk protein concentrate. Groups: Supplemented group vs. isocaloric placebo group for 24 weeks.	Significant differential increase in lean body mass in intervention group, but no significant differential change in strength and physical performance between groups.	Yes, both groups received resistance-type exercise training.
Kang 2019 [17]	n = 115, age ≥ 60 years, met at least 2 of 5 components of Fried’s physical frailty.	Nutritional supplementation: Nutrasumma whey protein. Groups: Supplemented group vs. control for 12 weeks.	Significant differential increase in hand-grip strength, gait speed, and chair-stand time.	Yes.
Park 2018 [18]	n = 120, age 70–85 years, met ≥1 of modified CHS frailty criteria, and MNA score ≤ 23.5.	Groups: 0.8 g whey protein/kg body weight supplementation vs. 1.2 g whey protein/kg body weight vs. 1.5 g protein/kg body weight 1:1:1 ratio for 12 weeks.	Significant differential increase in appendicular skeletal muscle mass (ASM), skeletal muscle mass index (SMI), and gait speed in 1.5 g protein/kg body weight group vs. 0.8 g protein/kg body weight group. No significant differential increase between 0.8 g protein/kg body weight and 1.2 g protein/kg body weight groups.	No, participants were told to maintain usual physical activity.
Yamada 2019 [19]	n = 112, age ≥ 65 years, met criteria for either sarcopenia or dynapenia.	Nutritional supplementation: 10.0 g whey protein + 800 IU Vitamin D. Groups: Exercise + nutritional supplement vs. exercise alone vs. nutritional supplement alone vs. control 1:1:1:1 ratio for 12 weeks.	Significant differential improvement in combined group’s appendicular muscle mass for sarcopenic adults, but not in adults with low physical function and normal muscle mass.	Yes, resistance program provided and part of randomization.
Amasene 2019 [20]	n = 41 (28 analyzed), age ≥ 70 years, met criteria for sarcopenia.	Nutritional supplement: 20 g whey protein isolate enriched with 3 g leucine. Groups: Supplemented group vs. isocaloric placebo for 12 weeks.	No significant differential improvement in physical function or muscle mass.	Yes, both groups followed a supervised resistance training program.
Chalé 2013 [21]	n = 80, age 70–85 years, SPPB score ≤ 10.	Nutritional Supplement: 40 g/day whey protein concentrate (20 g protein, 25 g maltodextrin). Groups: Supplemented group vs. isocaloric control.	No significant differential improvement between the supplemented group and control group.	Yes, resistance training protocol 3×/week for 6 months.
Daly 2014 [22]	n = 100, age 60–90 years, healthy.	Nutritional supplementation: 160 g cooked lean red meat. Groups: Red meat + resistance training vs. resistance training alone.	Red meat + PRT group experienced significantly greater gains in total body lean tissue mass, leg lean tissue mass, and muscle strength than control.	Yes, 45–60 min resistance training program for all participants.

CHS = Cardiovascular Health Study, SPPB = Short Physical Performance Battery, PRT = Progressive Resistance Training.