TABLE 2.
Summary of the included studies in model 3 (effect of protein source/quality when combined with resistance exercise training on longer-term adaptations to lean body mass and strength) in young and older adults1
| Study ID, author, y | Study arm | Participants, n | Body mass, kg | Group, age, y | Sex, M/F | Protein dose, g · d−1 | EAA dose,2 g · d−1 | Resistance exercise training protocol | Diet control | LBM | Muscle strength | Summary of main findings |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Brown, 2004 (33) | Young | |||||||||||
| Whey | 9 | 81 ± 3 | 20 ± 0 | M | 33 | 12.3 | 9-wk whole-body strength training incorporating 14 exercises; 3 sets of 4–6 repetitions | Diet record | ↑ | — | NSD between whey and soy in the relative change in LBM (+2.2 ± 2.1 vs. +1.7 ± 1.8%) in experienced male weightlifters | |
| Soy | 9 | 79 ± 5 | 22 ± 0 | M | 33 | 7.2 | ↑ | — | ||||
| Fabre, 2017 (34) | Young | |||||||||||
| 100% fast protein [FP(100)] | 10 | 74 ± 7 | 27 ± 6 | M | 20 | 6.1 | 9-wk whole-body resistance training. Participants trained 4 d per-wk and every 3-wks, the 1RM was increased from ∼60% 1RM to 85% 1RM with repetitions lowered | Yes + Diet record | ↑ | ↑ | NSD in LBM between FP(100) (pre: 58.9 ± 6.8 vs. post: 60.4 ± 7.0 kg) and FP(20) (pre: 62.0 ± 5.4 vs. post: 63.4 ± 5.0 kg) in recreationally resistance-trained men. NSD in squat 1RM between FP(100) (pre: 96 ± 26 vs. post: 111 ± 26 kg) and FP(20) (pre: 97 ± 17 vs. post: 111 ± 17 kg) | |
| 20% fast protein [FP(20)] | 10 | 78 ± 7 | 26 ± 5 | M | 20 | 5.2 | ↑ | ↑ | ||||
| Gryson, 2014 (35) | Old | |||||||||||
| Leucine-rich protein (Prolacta) | 8 | 84 ± 2 | 61 ± 1 | M | 10 | 5.2 | 16-wk, 3 sessions per-wk, concurrent endurance and resistance exercise training involving whole-body resistance training with load progressively increased throughout the training program | Diet record | ↔ | ↑ | NSD in LBM between Prolacta (pre: 60.1 ± 8.8 vs. post: 60.7 ± 8.2 kg) and PL (pre: 62.3 ± 6.3 vs. post: 63.1 ± 7.2) in older healthy men. NSD in MVC between Prolacta (pre: 647 ± 40 vs. post: 662 ± 51 N) and PL (pre: 632 ± 51 vs. post: 650 ± 63 N) | |
| Placebo milk drink (containing 4 g of total milk protein) | 9 | 82 ± 1 | 61 ± 1 | M | 10 | 1.7 | ↔ | ↑ | ||||
| Hamarsland, 2019 (36) | Old | |||||||||||
| Native whey | 15 | 78 ± 16 | 73 ± 2 | M = 9; F = 6 | 40 | 20.4 | 11-wk whole-body resistance training program; 3 sessions per-wk comprising loads between 6RM and 12RM | Diet record | ↑ | ↑ | NSD in LBM between native whey (pre: 49.5 ± 10.9 vs. post: 51.3 ± 10.9 kg) and milk (pre: 49.8 ± 9.2 vs. post: 52.1 ± 9.2 kg) in healthy, active elderly men and women. NSD in leg press 1RM between native whey (pre: 158 ± 50 vs. post: 212 ± 63 kg) and milk (pre: 176 ± 55 vs. post: 222 ± 56 kg) | |
| Milk | 15 | 75 ± 14 | 74 ± 4 | M = 9; F = 6 | 38.2 | 17.2 | ↑ | ↑ | ||||
| Hamarsland, 2019 (37) | Young | |||||||||||
| Native whey | 18 | 78 ± 12 | 29 ± 6 | M = 10; F = 8 | 40 | 20.4 | 12-wk whole-body resistance training; 3 sessions per-wk comprising loads between 6RM and 12RM | Diet record | ↑ | ↑ | NSD in LBM between native whey (pre: 54.2 ± 8.0 vs. post: 57.2 ± 8.2 kg) and milk (pre: 53.2 ± 10.7 vs. post: 55.8 ± 11.4 kg) in young untrained individuals. NSD in leg press 1RM between native whey (pre: 269 ± 77 vs. post: 344 ± 83 kg) and milk (pre: 266 ± 80 vs. post: 343 ± 74 kg) | |
| Dried milk | 18 | 78 ± 16 | 29 ± 6 | M = 10; F = 8 | 38.2 | 17.2 | ↑ | ↑ | ||||
| Hartman, 2007 (20) | Young | |||||||||||
| Milk | 18 | 79 ± 3 | 18–303 | M | 35 | ∼15.1 | Whole-body resistance training for 12-wk, 3 sessions per-wk. Participants completed 3–4 sets with repetitions between 6 and 12 at 80% 1RM | Diet record | ↑ | ↑ | Milk demonstrated a significantly greater increase in DXA-measured fat- and bone-free mass (pre: 62.4 ± 1.7 vs. post: 66.3 ± 1.6 kg) compared with soy (pre: 64.0 ± 2.5 vs. post: 66.8 ± 2.5 kg) in young, novice, male weightlifters. NSD in incline leg press 1RM between milk (pre: 186 ± 11 vs. post: 377 ± 18 kg) and soy (pre: 213 ± 15 vs. post: 423 ± 32 kg) | |
| Soy | 19 | 83 ± 4 | 18–303 | M | 35 | ∼11.9 | ↑ | ↑ | ||||
| Joy, 2013 (38) | Young | |||||||||||
| Whey isolate | 12 | 76 ± 6 | 21 ± 2 | M | 48 | 25.1 | 8-wk whole-body resistance training consisting of 'hypertrophy' sessions (8–12RM) and strength sessions (2–5RM). Participants trained twice per-wk | Yes | ↑ | ↑ | NSD in LBM between whey isolate (pre: 59.6 ± 5.2 vs. post: 62.8 ± 5.2 kg) and rice isolate (pre: 58.5 ± 5.5 vs. post: 61.0 ± 5.6 kg) in young resistance-trained males. NSD in leg press 1RM between whey isolate (pre: 210 ± 35 vs. post: 290 ± 40 kg) and rice isolate (pre: 220 ± 39 vs. post: 287 ± 37 kg) | |
| Rice isolate | 12 | 76 ± 6 | 21 ± 2 | M | 48 | 17.4 | ↑ | ↑ | ||||
| Lynch, 2020 (39) | Young | |||||||||||
| Whey | 26 | 67 ± 10 | 18–353 | M = 10; F = 16 | 19 | 9.2 | Whole-body resistance training for 12-wk, 3 sessions per-wk. Training sessions varied between 60% and 80% 1RM | Diet record | ↑ | ↑ | NSD in LBM between whey (pre: 44.5 ± 8.7 vs. post: 46.0 ± 8.9 kg) and soy (pre: 44.1 ± 10.3 vs. post: 45.2 ± 10.3 kg) in untrained young men and women. NSD in peak knee flexion or extension torque between whey (pre: 124 ± 40 vs. post: 164 ± 40 N·m) and soy (pre: 132 ± 45 vs. post: 160 ± 44 N·m) | |
| Soy | 22 | 66 ± 13 | 18–353 | M = 7; F = 15 | 26 | 9.5 | ↑ | ↑ | ||||
| Thomson, 2016 (40) | Old | |||||||||||
| High dairy protein | 54 | 79 ± 15 | 61 ± 7 | M = 25; F = 29 | 274 | NR | Whole-body resistance training for 12-wk, 3 sessions per-wk; 4 sets per exercise varying from 8–12 repetitions | Yes | ↑ | ↑ | NSD in LBM between high dairy protein diet (pre: 49.6 ± 11.0 vs. post: 50.6 ± 11.2 kg) and high soy protein diet (pre: 49.4 ± 11.2 vs. post: 50.8 ± 11.2 kg) in healthy older adults. NSD in knee extensor MVC between high dairy protein diet (pre: 132 ± 55 vs. post: 158 ± 62 kg) and high soy protein diet (pre: 142 ± 62 vs. post: 161 ± 62 N·m). | |
| High soy protein | 64 | 79 ± 13 | 62 ± 8 | M = 29; F = 35 | 274 | NR | ↑ | ↑ | ||||
| Significant difference in total body 8RM between high dairy protein (pre: 149 ± 51 vs. post: 280 ± 88 kg; change: 131 ± 54 kg) and high soy protein (pre: 169 ± 79 vs. post: 271 ± 122 kg; change: 102 ± 51 kg) | ||||||||||||
| Wilborn, 2013 (41) | Young | |||||||||||
| Whey | 8 | 66 ± 5 | 20 ± 2 | F | 48 | ∼21.3 | 8-wk periodized resistance training program consisting of 2 upper-body and 2 lower-body workouts per-wk (4 sessions per-wk). Sport-specific training was completed alongside (basketball) | Diet record | ↑ | ↑ | NSD between whey (2.3 ± 1.5%) and casein (2.1 ± 1.5%) in the relative change of LBM in trained female basketball players. Casein and whey supplement groups both experienced significant strength gains for both leg press 1RM (whey: 88.7 ± 43.9 kg; casein: 90.0 ± 48.5 kg) and bench press 1RM (whey: 7.5 ± 4.6 kg; casein: 4.3 ± 4.5 kg), but there was no significant between-group difference in strength gains | |
| Casein | 8 | 68 ± 3 | 21 ± 3 | F | 48 | ∼20.3 | ↑ | ↑ |
1
Values are means ± SDs. Arrows represent increase or decrease in lean body mass and/or strength. FP, fast protein; LBM, lean body mass; MPS, muscle protein synthesis; MVC, maximum voluntary contraction; NSD, no significant difference; NR, not reported; PL, placebo; RM, repetition maximum.
2
Where EAA content was not provided, total content is provided as estimates based on information provided within each study, where possible.
3
Age ranges provided in the absence of means ± SDs.
4
The 27-g protein supplement was provided in addition to high dairy/soy protein diet, respectively.