Soy Protein

Does soy protein work?

What is soy protein?

Few foods evoke greater emotion than soy. It elicits fears of decreased testosterone, less optimal strength, and feminization of masculine features. There’s plenty of misinformation about soy. The truth is there are plenty of health and performance benefits to consuming soy protein with plenty of research to back it up. Read More


Overall Effectiveness Rating for Soy Protein

The overall effectiveness rating for soy protein is 2 out of 3. This rating means there is some evidence that using soy protein may lead to positive results. This rating also means that some evidence does not back up all claims. Below you can find individual ratings for specific claims.

Overall Confidence Rating for Soy Protein

There are 14 studies in the database on soy protein; the confidence rating is 42. A score above 80 means the effectiveness rating for this supplement is reliable. A score under 80 means there is insufficient evidence to ensure a reliable effectiveness rating. Note, this rating is for soy protein as a whole. There are also individual ratings for the claims below.

Individual Claims

The overall ratings above do no necessarily reflect each claim about soy protein. Individual claims can have higher or lower ratings. For example, some supplements may have a lot of backing for one claim, but be completely useless for another. Click on claims below for more information.

Body Composition (weight, muscle, body fat) Claims Effectiveness Rating Confidence Rating
decrease body fat
increase muscle mass
increase weight loss

Protein Synthesis Claims Effectiveness Rating Confidence Rating
increase protein synthesis

Performance Claims Effectiveness Rating Confidence Rating
increase strength

Hormone Function Claims Effectiveness Rating Confidence Rating
decrease testosterone

Cardiovascular Health Claims Effectiveness Rating Confidence Rating
lower LDL (bad) cholesterol levels
increase HDL (good) cholesterol levels
lower total cholesterol levels

Recovery Claims Effectiveness Rating Confidence Rating
reduce muscle damage


Title of Study
Clinical and biological activity of soy protein powder supplementation in healthy male volunteers
Clinical studies show no effects of soy protein or isoflavones on reproductive hormones in men: results of a meta-analysis
Consumption of fat-free fluid milk after resistance exercise promotes greater lean mass accretion than does consumption of soy or carbohydrate in young, novice, male weightlifters
Effect of soy and milk protein supplementation on serum lipid levels: a randomized controlled trial
Effect of whey and soy protein supplementation combined with resistance training in young adults
Effects of Whey, Soy or Leucine Supplementation with 12 Weeks of Resistance Training on Strength, Body Composition, and Skeletal Muscle and Adipose Tissue Histological Attributes in College-Aged Males
Four Weeks of Supplementation With Isolated Soy Protein Attenuates Exercise-Induced Muscle Damage and Enhances Muscle Recovery in Well Trained Athletes: A Randomized Trial
Ingestion of whey hydrolysate, casein, or soy protein isolate: effects on mixed muscle protein synthesis at rest and following resistance exercise in young men
Muscle strength gains during resistance exercise training are attenuated with soy compared with dairy or usual protein intake in older adults: A randomized controlled trial
One-year soy protein supplementation does not improve lipid profile in postmenopausal women
Soy protein intake by active young adult men raises plasma antioxidant capacity without altering plasma testosterone
Supplementation with soy-protein-rich foods does not enhance weight loss
The effects of soy and whey protein supplementation on acute hormonal reponses to resistance exercise in men
Whey Protein Supplementation During Resistance Training Augments Lean Body Mass