Soy protein for muscle, recovery and performance in athletes
What it found
In 19 randomised trials in active people and athletes, soy protein built lean mass about as well as whey, and showed some benefits for antioxidant status and endurance performance.
Results for testosterone and VO2 max were mixed.
What they found
Studies in people
Lean mass and strength
Several trials found soy protein gave similar increases in lean mass and strength to whey protein, especially when daily protein intake was at least 1.6 g per kg body weight. At lower protein intakes, whey had a slight edge in some measures.
Antioxidant status
Long-term soy protein supplementation (4 to 9 weeks) reduced markers of oxidative stress such as lipid peroxides and myeloperoxidase, and helped maintain antioxidant capacity, compared with whey or placebo.
Metabolic markers
Soy protein reduced exercise-induced rises in triglycerides, uric acid and lactate, and lowered creatine kinase after strenuous training in some studies.
Hormones
Findings on testosterone and cortisol were inconsistent. Some studies found changes, others found none. Insulin rose after soy intake in a few studies.
Exercise performance
All six performance studies suggested soy protein helped endurance, high-intensity running, fatigue resistance or muscle strength. Two studies on VO2 max gave conflicting results.
Muscle protein synthesis
In acute studies, soy and whey both increased muscle protein synthesis after exercise, though whey raised blood leucine more. A soy-dairy blend gave a longer-lasting amino acid balance in one study.
What the authors conclude
“It is possible to recommend SP to athletes and active individuals in place of conventional protein supplements by assessing their dosage and effectiveness in relation to different types of training.”
Also in their conclusions
- They say it is possible to recommend soy protein to athletes and active individuals in place of conventional protein supplements, after assessing dosage and training type.
- They note that soy protein may enhance lean mass compared with other protein sources, improve antioxidant status and reduce oxidative stress.
- They advise that soy protein may be especially beneficial after muscle damage, high-intensity exercise or repeated strenuous bouts.
How it was done
Soy protein has become a popular plant-based alternative to animal proteins, but its effects on muscle, metabolism, hormones and performance in active people had not been reviewed together.
The authors searched three databases for randomised controlled trials of soy protein supplementation in active people and athletes aged 14 to 39. They found 19 eligible trials, covering muscle adaptations, metabolic and antioxidant status, hormonal response and exercise performance.
What it can’t tell you
- The trials used different doses, durations and types of soy, so the best dose and timing are not clear.
- Most studies were small and some had concerns about bias, such as lack of supervision on diet and exercise.
- The findings may apply mainly to generally active young people, not to all athletes or older adults.
Who paid
- Conflicts
- All authors declare that they have no conflict of interest relevant to the content of this review.
- Authors work at
- Istanbul Medeniyet University, Turkey; Dublin City University, Ireland; University of Piemonte Orientale, Italy
The paper
- Title
- Effect of Soy Protein Supplementation on Muscle Adaptations, Metabolic and Antioxidant Status, Hormonal Response, and Exercise Performance of Active Individuals and Athletes: A Systematic Review of Randomised Controlled Trials
- Type
- Systematic review
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Zare R, Devrim-Lanpir A, Guazzotti S, et al (2023). Effect of Soy Protein Supplementation on Muscle Adaptations, Metabolic and Antioxidant Status, Hormonal Response, and Exercise Performance of Active Individuals and Athletes: A Systematic Review of Randomised Controlled Trials. Sports medicine (Auckland, N.Z.). doi:10.1007/s40279-023-01899-wFree full textPubMed 37603200DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error