Semester

Spring

Date of Graduation

2025

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Committee Chair

Janet Tou

Committee Co-Chair

Jianbo Yao

Committee Member

Jianbo Yao

Committee Member

Joseph Gigliotti

Abstract

Background: Whey protein is a popular supplement in sports nutrition. Soy protein is an alternative to whey protein, often marketed to individuals following a plant-based diet. Evaluating whey and soy protein supplementation's role in resistance exercise is essential for providing evidence-based nutrition guidance.

Objective: The study aim was to conduct a systematic literature review and meta-analysis on randomized control trials (RCTs) on the effectiveness of whey and soy protein supplementation on outcomes of lean body mass (LBM), squat, bench press, and plasma essential plasma amino acid (EAA) levels in young adult men and women.

Methods: The databases searched included: Cochrane, EBSCO Host, PubMed, and Scopus. Inclusion criteria were interventions that included whey or soy protein concentrate or isolate and participants aged 18 to 30 years who engage in resistance exercise. Exclusion criteria were randomized control trials (RCTs), protein supplements with additives, and unspecified protein supplements. Two reviewers independently evaluated 1813 studies based on the inclusion and exclusion criteria. Studies that met these criteria underwent data extraction for LBM, squat, bench press, and circulating EAA. The studies were assessed for risk of bias was assessed using the Cochrane RoB 2 tool for RCTs. A meta-analysis was performed using a random-effects model.

Results: The review included a total of 12 studies with 261 participants. There was no significant effect of supplementing whey or soy protein intervention on LBM mean difference (MD) (1.13; 95% CI: -0.76, 3.02; p=0.22, I2 =55.7%), squat performance (MD 4.06; 95% CI:-5.46, 13.57; p=0.34, I2 =77.5%). However, whey protein supplementation had a significant effect on bench press (MD 5.72; 95% CI:1.30, 10.15; p=0.02, I2 =61.2%).

Conclusion: These findings suggest that while both whey and soy proteins can be part of a resistance training regimen, whey protein may offer a specific advantage in enhancing upper body strength in young adults engaging in resistance training. Due to the small number of studies and sample size, these findings should be interpreted with caution. Further research with larger-powered randomized controlled trials is necessary to provide more definitive conclusions regarding the effectiveness of protein supplements for enhancing strength performance.

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