Protein Supplementation Has Minimal Effects on Muscle Adaptations during Resistance Exercise Training in Young Men: A Double-Blind Randomized Clinical Trial

Abstract

Background: To our knowledge the efficacy of soy-dairy protein blend (PB) supplementation with resistance exercise training (RET) has not been evaluated in a longitudinal study.Objective: Our aim was to determine the effect of PB supplementation during RET on muscle adaptation.Methods: In this double-blind randomized clinical trial, healthy young men [18–30 y; BMI (in kg/m2): 25 ± 0.5] participated in supervised whole-body RET at 60–80% 1-repetition maximum (1-RM) for 3 d/wk for 12 wk with random assignment to daily receive 22 g PB (n = 23), whey protein (WP) isolate (n = 22), or an isocaloric maltodextrin (carbohydrate) placebo [(MDP) n = 23]. Serum testosterone, muscle strength, thigh muscle thickness (MT), myofiber cross-sectional area (mCSA), and lean body mass (LBM) were assessed before and after 6 and 12 wk of RET.Results: All treatments increased LBM (P < 0.001). ANCOVA did not identify an overall treatment effect at 12 wk (P = 0.11). There tended to be a greater change in LBM from baseline to 12 wk in the PB group than in the MDP group (0.92 kg; 95% CI: −0.12, 1.95 kg; P = 0.09); however, changes in the WP and MDP groups did not differ. Pooling data from combined PB and WP treatments showed a trend for greater change in LBM from baseline to 12 wk compared with MDP treatment (0.69 kg; 95% CI: −0.08, 1.46 kg; P = 0.08). Muscle strength, mCSA, and MT increased (P < 0.05) similarly for all treatments and were not different (P > 0.10) between treatments. Testosterone was not altered. Conclusions: PB supplementation during 3 mo of RET tended to slightly enhance gains in whole-body and arm LBM, but not leg muscle mass, compared with RET without protein supplementation. Although protein supplementation minimally enhanced gains in LBM of healthy young men, there was no enhancement of gains in strength. This trial was registered at clinicaltrials.gov as NCT01749189.

Protein Supplementation Does Not Affect Myogenic Adaptations to Resistance Training

“…There were no differences between treatments at pre for any of the descriptive characteristics (p>0.10). As our previous report indicated (38), the habitual protein intake for participants was ∼1.3 g/kg/d and the participants increased protein intake in both protein supplement groups above this level.…”

“…Participant were of similar age (PB: 24.1±0.6; WP: 24.6±1.0; MDP 25.2±1.1), height (PB: 178.6.1±1.5; WP: 180.0.6±2.1; MDP 176.0±1.6) weight (PB: 77.51±2.3; WP: 83.5±3.4; MDP 76.3±1.3), BMI (PB: 24.3±0.6; WP: 25.7±0.9; MDP 24.5±0.8), whole body lean mass (PB: 56.2±1.3; WP: 58.9±2.3; MDP 55.4±1.7), and leg lean mass (PB: 19.0±0.4; WP: 20.7±1.0; MDP 18.7±0.8) at pre. The subjects included in this study were a subset of a larger clinical trial (38), where screening and enrollment details can be found alongside information concerning treatment compliance, dietary intake and strength testing. There were no differences between treatments at pre for any of the descriptive characteristics (p>0.10).…”

“…The study design can be found in more detail elsewhere (38), briefly, following enrollment, completion of a run-in period consisted of the pre-training study day at UTMB and then 3 non-consecutive days of exercise familiarization and pre 1-repetition max (1-RM) strength testing at the University of Texas Medical Branch Alumni Fieldhouse. The pre-training study day included assessment of body composition, a muscle biopsy and a isometric and isokinetic strength test of the thigh as we have previously described in the initial clinical trial (38).…”

“…The pre-training study day included assessment of body composition, a muscle biopsy and a isometric and isokinetic strength test of the thigh as we have previously described in the initial clinical trial (38). Soon after, the participants reported to the UTMB Alumni Fieldhouse for familiarization/testing before beginning 12 weeks of training.…”

Soy and Health Update: Evaluation of the Clinical and Epidemiologic Literature

“…More specifically, a systematic review and meta-analysis that included 15 placebo-controlled treatment groups with baseline and ending measures and an additional 32 reports involving 36 treatment groups found no effects of soy protein or isoflavone intake on testosterone, sex hormone binding globulin, free testosterone or the free androgen index [283]. Studies published subsequent to this meta-analysis have reached similar conclusions [168,392,393,394]. The two aforementioned case reports simply illustrate that consuming excessive amounts of essentially any food can potentially lead to abnormalities [389,390].…”