Effects of slow- v. fast-digested protein supplementation combined with mixed power training on muscle function and functional capacities in older men

Comparative Efficacy of Different Protein Supplements on Muscle Mass, Strength, and Physical Indices of Sarcopenia among Community-Dwelling, Hospitalized or Institutionalized Older Adults Undergoing Resistance Training: A Network Meta-Analysis of Randomized Controlled Trials

Aging-related sarcopenia exerts harmful impacts on muscle mass, strength, and physical mobility. Protein supplementation has been demonstrated to augment efficacy of resistance training (RT) in elderly. This study compared the relative effects of different protein supplements on muscle mass, strength, and mobility outcomes in middle-aged and older individuals undergoing RT. A comprehensive search of online databases was performed to identify randomized controlled trials (RCTs) examining the efficacy of protein supplement plus RT in untrained community-dwelling adults, hospitalized, or institutionalized residents who suffered acute or chronic health conditions. Network meta-analysis (NMA) was performed using a frequentist method for all analyses. Treatment effects for main outcomes were expressed as standard mean difference (SMD) with 95% confidence interval (CI). We used the surface-under-the cumulative-ranking (SUCRA) scores to rank probabilities of effect estimation among all identified treatments. Meta-regression analyses were performed to identify any relevant moderator of the treatment efficacy and results were expressed as β with 95% credible interval (CrI). We finally included 78 RCTs (5272 participants) for analyses. Among the six protein sources identified in this NMA, namely whey, milk, casein, meat, soy, and peanut, whey supplement yielded the most effective treatments augmenting efficacy of RT on muscle mass (SMD = 1.29, 95% CI: 0.96, 1.62; SUCRA = 0.86), handgrip strength (SMD = 1.46, 95% CI: 0.92, 2.00; SUCRA = 0.85), and walking speed (SMD = 0.73, 95% CI: 0.39, 1.07; SUCRA = 0.84). Participant's health condition, sex, and supplementation dose were significant factors moderating the treatment efficacy on muscle mass (β = 0.74; 95% CrI: 0.22, 1.25), handgrip strength (β = -1.72; 95% CrI: -2.68, -0.77), and leg strength (β = 0.76; 95% CrI: 0.06, 1.47), respectively. Our findings suggest whey protein yields the optimal supplements to counter sarcopenia in older individuals undergoing RT.

Effects of resistance training and protein supplementation interventions on muscle volume and muscle function: sex differences in humans

PURPOSE

This review aimed to identify differences in the effects of co-intervention with resistance training (RT) and protein supplementation according to sex and provide meaningful information for future research on the development of exercise programs to improve muscle volume and muscle function.

METHODS

PubMed, Science Direct, and Google Scholar were searched to identify clinical and nonclinical studies that assessed the effects of RT in older adults with sarcopenia; these studies were published between 1990 and 2023. Cross-sectional and double-blind studies (randomized controlled trials, RCTs) were examined in this review.

RESULTS

The effects of parallel intervention with RT and protein supplementation on muscle volume and physical function were found to differ according to sex. Both males and females had improvements in muscle strength, muscle mass, and physical function after RT and protein supplementation; however, many studies found a greater increase in muscle volume and function in males than in females. Such difference may be due to differences in physiological characteristics between males and females.

CONCLUSION

Based on the findings of this review, the effects of combined intervention with RT and protein supplementation on muscle strength, muscle mass, and physical function to differ according to sex. Owing to these sex differences in the response and physiological characteristics caused by the parallel intervention of RT and protein supplementation, such differences must be considered to maximize the effects of RT and protein supplementation.

Whey Protein Supplementation with or without Vitamin D on Sarcopenia-Related Measures: A Systematic Review and Meta-Analysis

The effects of supplementation with whey protein alone or with vitamin D on sarcopenia-related outcomes in older adults are unclear. We aimed to assess the effect of whey protein supplementation alone or with vitamin D on lean mass (LM), strength, and function in older adults with or without sarcopenia or frailty. We searched PubMed, Web of Science, and SCOPUS databases. Randomized controlled trials (RCT) that investigated the effect of whey protein supplementation with or without vitamin D on sarcopenia outcomes in healthy and sarcopenic or frail older adults were included. Standardized mean differences (SMDs) were calculated for LM, muscle strength, and physical function data. The analysis showed that whey protein supplementation had no effect on LM and muscle strength; nevertheless, a significant improvement was found in physical function (SMD = 0.561; 95% confidence interval [CIs]: 0.256, 0.865, n = 33), particularly gait speed (GS). On the contrary, whey protein supplementation significantly improved LM (SMD = 0.982; 95% CI: 0.228, 1.736; n = 11), appendicular lean mass and physical function (SMD = 1.211; 95% CI: 0.588, 1.834; n = 16), and GS in sarcopenic/frail older adults. By contrast, co-supplementation with vitamin D enhanced LM gains (SMD =0.993; 95% CI: 0.112, 1.874; n = 11), muscle strength (SMD =2.005; 95% CI: 0.975, 3.035; n = 11), and physical function (SMD = 3.038; 95% CI: 2.196, 3.879; n = 18) significantly. Muscle strength and physical function improvements after whey protein supplementation plus vitamin D were observed without resistance exercise (RE) and short study duration subgroups. Moreover, the combination of whey protein and vitamin D with RE did not enhance the effect of RE. Whey protein supplementation improved LM and function in sarcopenic/frail older adults but had no positive effect in healthy older persons. By contrast, our meta-analysis showed that co-supplementation with whey protein and vitamin D is effective, particularly in healthy older adults, which is likely owing, we propose, to the correction of vitamin D insufficiency or deficiency. The trial was registered at https://inplasy.com as INPLASY202240167.

Which intervention is more effective in improving sarcopenia in older adults? A systematic review with meta-analysis of randomized controlled trials

This systematic review aims, however, to determine which intervention is more effective. The skeletal muscle index (SMI), handgrip, and gait speed were used as indicators of improvement, and these effects were compared across six subgroups: combined intervention versus exercise; nutrition or control group; exercise versus nutrition; and exercise or nutrition versus control group. Out of 1596 articles, 32 studies (3063 older adults) were selected and meta-analyzed. Comparing the combined intervention with a control group, the WMD was 0.20 kg/m², 1.56 kg, and 0.08 m/s for SMI, handgrip, and gait speed, respectively, all of which showed a statistically significant improvement. When a combined intervention was compared with exercise and nutrition, the former resulted in improvements in handgrip (WMD 0.38 kg) and gait speed (WMD 0.12 m/s). On comparing exercise and nutrition, there was an improvement in gait speed (0.12 m/s) with exercise alone. On comparing exercise with a control group, only handgrip (WMD 1.74 kg) and gait speed (WMD 0.11 m/s) showed improvement, whereas in the nutrition versus the control group, only the handgrip (WMD 0.90 kg) improved. Although exercise and nutritional therapy together demonstrated improved muscle strength, exercise is recommended for the improvement of physical performance.

Changes in 24-h energy expenditure, substrate oxidation, and body composition following resistance exercise and a high protein diet via whey protein supplementation in healthy older men

PURPOSE

To investigate changes in 24-h energy expenditure (EE), substrate oxidation, and body composition following resistance exercise (RE) and a high protein diet via whey protein supplementation (alone and combined) in healthy older men.

METHODS

In a pooled groups analysis, 33 healthy older men [(mean ± SE) age: 67 ± 1 years; BMI: 25.4 ± 0.4 kg/m2] were randomized to either RE (2×/week; n = 17) or non-exercise (n = 16) and either a high protein diet via whey protein supplementation (PRO, 2 × 25 g whey protein isolate/d; n = 17) or control (CON, 2 × 23.75 g maltodextrin/d; n = 16). An exploratory sub-analysis was also conducted between RE+CON (n = 8) and RE+PRO (n = 9). At baseline and 12 weeks, participants resided in respiration chambers for measurement of 24-h EE and substrate oxidation and wore an accelerometer for 7 days for estimation of free-living EE.

RESULTS

Resistance exercise resulted in greater increases in fat-free mass (1.0 ± 0.3 kg), resting metabolic rate [(RMR) 36 ± 14 kcal/d], sedentary EE (60 ± 33 kcal/d), and sleeping metabolic rate [(SMR) 45 ± 7 kcal/d] compared to non-exercise (p < 0.05); however, RE decreased activity energy expenditure in free-living (-90 ± 25 kcal/d; p = 0.049) and non-exercise activity inside the respiration chamber (-1.9 ± 1.1%; p = 0.049). PRO decreased fat mass [(FM) -0.5 ± 0.3 kg], increased overnight protein oxidation (30 ± 6 g/d), and decreased 24-h protein balance (-20 ± 4 g/d) greater than CON (p < 0.05). RE+PRO decreased FM (-1.0 ± 0.5 kg) greater than RE+CON (p = 0.04).

CONCLUSION

Resistance exercise significantly increased RMR, SMR, and sedentary EE in healthy older men, but not total EE. PRO alone and combined with RE decreased FM and aided body weight maintenance. This study was registered at clinicaltrials.gov as NCT03299972.

Systematic review and meta-analysis of protein intake to support muscle mass and function in healthy adults

We performed a systematic review, meta-analysis, and meta-regression to determine if increasing daily protein ingestion contributes to gaining lean body mass (LBM), muscle strength, and physical/functional test performance in healthy subjects. A protocol for the present study was registered (PROSPERO, CRD42020159001), and a systematic search of Medline, Embase, CINAHL, and Web of Sciences databases was undertaken. Only randomized controlled trials (RCT) where participants increased their daily protein intake and were healthy and non-obese adults were included. Research questions focused on the main effects on the outcomes of interest and subgroup analysis, splitting the studies by participation in a resistance exercise (RE), age (<65 or ≥65 years old), and levels of daily protein ingestion. Three-level random-effects meta-analyses and meta-regressions were conducted on data from 74 RCT. Most of the selected studies tested the effects of additional protein ingestion during RE training. The evidence suggests that increasing daily protein ingestion may enhance gains in LBM in studies enrolling subjects in RE (SMD [standardized mean difference] = 0.22, 95% CI [95% confidence interval] 0.14:0.30, P < 0.01, 62 studies, moderate level of evidence). The effect on LBM was significant in subjects ≥65 years old ingesting 1.2-1.59 g of protein/kg/day and for younger subjects (<65 years old) ingesting ≥1.6 g of protein/kg/day submitted to RE. Lower-body strength gain was slightly higher by additional protein ingestion at ≥1.6 g of protein/kg/day during RE training (SMD = 0.40, 95% CI 0.09:0.35, P < 0.01, 19 studies, low level of evidence). Bench press strength is slightly increased by ingesting more protein in <65 years old subjects during RE training (SMD = 0.18, 95% CI 0.03:0.33, P = 0.01, 32 studies, low level of evidence). The effects of ingesting more protein are unclear when assessing handgrip strength and only marginal for performance in physical function tests. In conclusion, increasing daily protein ingestion results in small additional gains in LBM and lower body muscle strength gains in healthy adults enrolled in resistance exercise training. There is a slight effect on bench press strength and minimal effect performance in physical function tests. The effect on handgrip strength is unclear.

Effects of resistance exercise and whey protein supplementation on skeletal muscle strength, mass, physical function, and hormonal and inflammatory biomarkers in healthy active older men: a randomised, double-blind, placebo-controlled trial

PURPOSE

To determine the individual and combined effects of 12 weeks of resistance exercise (RE) and whey protein supplementation on skeletal muscle strength (primary outcome), mass and physical function, and hormonal and inflammatory biomarkers in older adults.

METHODS

Thirty-six healthy older men [(mean±SE) age: 67±1 y; BMI: 25.5±0.4 kg/m²] were randomised to either control (CON; n=9), whey protein (PRO; n=9), RE+control (EX+CON; n=9), or RE+whey protein (EX+PRO; n=9) in a double-blinded fashion. Whole-body RE (2 sets of 8 repetitions and 1 set to volitional failure at 80% 1RM) was performed twice weekly. Supplements (PRO, 25 g whey protein isolate; CON, 23.75 g maltodextrin) were consumed twice daily.

RESULTS

EX+CON and EX+PRO increased leg extension (+19±3 kg and +20±3 kg, respectively) and leg press 1RM (+27±3 kg and +39±2 kg, respectively) greater than the CON and PRO groups (P<0.001, Cohen's d=1.50-1.90). RE (EX+CON and EX+PRO groups pooled) also increased fat-free mass (FFM) (+0.9±0.3 kg) and 6-min walk test distance (+21±5 m) and decreased fat mass (-0.4±0.4 kg), and interleukin-6 (-1.0±0.4 pg/mL) and tumor necrosis factor-alpha concentration (-0.7±0.3 pg/mL) greater than non-exercise (CON and PRO groups pooled; P<0.05, Cohen's f=0.37-0.45). Whey protein supplementation (PRO and EX+PRO groups pooled) increased 4-m gait speed greater than control (CON and EX+CON groups pooled) (+0.08±0.03 m/s; P=0.007, f=0.51).

CONCLUSION

RE increased muscle strength, FFM and physical function, and decreased markers of systemic inflammation in healthy active older men. Whey protein supplementation alone increased gait speed. No synergistic effects were observed. This study was registered at clinicaltrials.gov as NCT03299972.

The Effects of a High-Protein Dairy Milk Beverage With or Without Progressive Resistance Training on Fat-Free Mass, Skeletal Muscle Strength and Power, and Functional Performance in Healthy Active Older Adults: A 12-Week Randomized Controlled Trial

The study aimed to investigate the independent and combined effects of consuming a high-protein dairy milk beverage, twice daily, with or without a progressive resistance training (PRT) program on outcomes of age-related sarcopenia, in healthy active older (≥50 years) adults. In this 12-week, 2 × 2 factorial study, participants were randomly allocated into one of four groups: dairy milk beverage (DM), exercise and dairy milk beverage (EX+DM), exercise alone (EX), and control (CON). The EX group underwent a 12-week whole-body PRT schedule (three sessions/week) and a high-protein dairy milk beverage (DM) was consumed twice daily (30 g protein/day). At weeks 0, 6, and 12, body composition (iDXA), strength [one-repetition maximum (1RM): leg press, chest press, lateral (lat) pull-down, and handgrip], power (countermovement jump), cardiorespiratory fitness (VO2), and physical performance (gait speed) were measured. Before measurements, blood samples were collected to determine the immune (i.e., leukocyte trafficking and inflammatory cytokines) and hormonal (i.e., insulin, cortisol, IGF-1, testosterone, and estradiol) profiles. Participants (n = 37) completed the study within the controlled experimental conditions. Protein intake increased in the EX+DM [mean ± SD, 1.2 ± 0.2 to 1.8 ± 0.4 g/kg body mass (BM) per day-1] and DM (1.3 ± 0.5 to 1.8 ± 0.6 g kg-1 BM day-1) groups during the intervention. Absolute fat-free mass increased in the EX+DM [mean (95% confidence interval) = 0.65 (0.25-1.0) kg] and EX [0.49 (-0.44 to 1.40) kg] groups (P < 0.001) compared to DM [-0.54 (-1.6 to 0.05) kg]. Relative fat mass decreased (group*time, P = 0.018) in DM [-1.8% (-3.3 to -0.35%)] and EX+DM [-1.3% (-2.3 to -0.31%)], which was a greater reduction than that in the CON [0.10% (-0.80 to 1.0%)] group (P < 0.01). Relative maximal strength increased in both the EX and EX+DM (≥35%, P < 0.05) groups, but not in the DM and CON groups. The change in 1RM strength outcomes was higher in EX+DM compared to all other groups (53-78%, P < 0.01). There was an increase in resting plasma IL-10 concentration in EX+DM (88%), compared to all the other groups (P = 0.016). No other differences in systemic inflammatory cytokines were observed. There were no significant changes in all hormone concentrations measured among all groups. In conclusion, a high-protein dairy milk beverage providing additional protein did not further enhance the effects of PRT on outcomes of fat-free mass, power, or physical performance. However, there was a significant augmentative effect for high-protein dairy milk consumption on changes to maximal strength outcomes during PRT in healthy active older adults.