Research

Hormonal

Soy protein supplementation has an inconsistent effect on testosterone and cortisol levels, and more research is required to determine its impact on anabolic hormones.

Don't worry about soy protein affecting your hormones. The research shows inconsistent effects on testosterone and cortisol, with no clear evidence of negative impacts. You can consume soy protein without fear of hormonal disruption.

LimitedQualifiesLOW confidence
Some studies reported testosterone and cortisol fluctuations related to SP; however, more research is required. SP supplementation had an inconsistent effect on testosterone and cortisol levels.
Reza Zare et al. · Sports Medicine · 2023

Why this rating

Based on a small number of studies (n=6) with conflicting results, requiring more research.

Source

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

Reza Zare et al. · Sports Medicine · 2023

DOI 10.1007/s40279-023-01899-w

systematic_reviewCited 37×
Read the paper
DOI resolved against Crossref · corpus check 2026-06-10

This is one finding among thousands. Every one is graded and traced to its source, so you can see what the evidence actually supports. Browse the research →