The Study
No Significant Differences in Muscle Growth and Strength Development When Consuming Soy and Whey Protein Supplements Matched for Leucine Following a 12 Week Resistance Training Program in Men and Women: A Randomized Trial
This study is like a fair test where people were randomly given either soy or whey protein while doing the same workout routine. It shows that both proteins work about the same for building muscle and strength when they have the same amount of a key ingredient called leucine.
Analysis score
Maximum 90 for a randomized controlled trial.
Where the score came from
This study tested if soy protein is as good as whey for helping beginners build muscle when both have the same amount of a key muscle-building amino acid called leucine.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 574 / 100
Quality score
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
Key takeaways
Summary
Based on the study abstract and findings.
- 1Yes, the results are meaningful—beginners can gain muscle and strength equally well with leucine-matched soy or whey protein.
- 2After 12 weeks, both groups gained about 1.5 kg of muscle and got stronger, no matter if they drank soy or whey protein.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
International Journal of Environmental Research and Public Health
Year
2020
Authors
Heidi M. Lynch, M. Buman, J. Dickinson, L. Ransdell, C. Johnston, Christopher M. Wharton
Related Content
Claims (5)
If you eat the same amount of protein and lift weights the same way, it doesn’t matter whether your protein is fast- or slow-digesting—even if it’s from plants like soy—your muscle gains will be about the same.
If young adults who aren't used to working out do strength training 3 times a week for 12 weeks, they’ll gain about 1.5 kg of muscle and get stronger legs — and it doesn’t matter if their protein shake is made from soy or whey, as long as both have the same amount of leucine (2 grams per day).
For young people new to lifting weights, taking soy protein or whey protein daily seems to have the same effect on thigh muscle growth.
If young adults who aren't used to working out eat a bit more protein—especially from whey or soy—and lift weights 3 times a week for 3 months, they’ll likely gain more muscle and get stronger, even if they weren’t eating enough protein to start with.
If you're a young adult just starting strength training, drinking a shake with either whey or soy protein—both with the same amount of a key muscle-building amino acid (leucine)—will help you gain muscle equally well over 12 weeks.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.