Final Verdict: Is soy protein worth taking?

soy protein

Final Verdict: Is soy protein worth taking?

Soy Protein

In our series on soy protein, we covered topics including its effects on testosterone, health benefits, and body composition. Here we’ll go over our findings and make a final recommendation on whether or not soy protein is worth taking.



In the mainstream gym blogosphere, soy protein is synonymous with decreased testosterone. We looked at some research to find out whether or not that’s true. The vast majority of the research indicates soy does not negatively affect testosterone. In one meta-analysis of over 30 studies, researchers concluded that soy protein does not alter testosterone levels1.

Verdict: The overwhelming amount of evidence does not support the theory that soy protein affects testosterone levels.

Read more: Does soy decrease testosterone levels?

Health Benefits

The research on soy’s ability to improve overall health is vast. Soy contains isoflavones, a substance found in plants that have beneficial health effects. There is plenty of literature indicating soy protein can decrease the risk of prostate cancer, heart disease, and breast cancer.

Verdict: The evidence suggests that replacing animal products with soy leads to many health benefits.

Read more: What are the health benefits of soy protein?


Protein supplements are best known for increasing strength when used with a resistance training program. Most of the gym world uses whey or casein supplements for this purpose, however, soy also has a role in improving strength. We looked at a few studies and found that soy protein led to similar strength increases when compared to both whey and casein products. In one meta-analysis of nine studies and 266 participants, researchers concluded that soy was a suitable option for strength and muscle gains2.

Verdict: There is plenty of evidence showing soy protein is just as good (sometimes even better) than other types of protein at increasing strength and muscle mass.

Read more: Does soy protein make you stronger?


The amount of research on whether soy protein improves endurance is limited. The research available suggests that soy protein may improve cardiovascular performance when used either before or after a workout.

Verdict: The research on whether or not soy protein specifically improves endurance is limited, but given the ample evidence showing protein, in general, enhances performance in many types of exercise, it is a safe assumption that soy provides similar benefits.

Read more: Does soy protein improve cardio?

Body Composition: Muscle Mass and Body Fat

There were a few studies we looked at on whether soy protein could increase muscle mass and/or decrease body fat. Most of the studies showed that soy significantly increased muscle mass in all participants including post-menopausal women, middle-aged males, and young males. On body fat, the results were a bit more mixed. Still, many of the studies did show body fat reductions when soy protein was combined with resistance training.

Verdict: When used with a resistance training program, soy protein leads to increased muscle mass and possibly, decreased body fat.

Read more: Does soy protein improve body composition?


Improving the recovery process is perhaps the most important reason to use a protein supplement. This process is what makes us bigger, faster, and stronger. Researchers measure recovery in terms of muscle damage, soreness, and how quickly someone can return to peak performance after a workout. The evidence shows soy protein can decrease inflammation, muscle damage, soreness, and preserve strength after a workout.

Verdict: The evidence indicates soy protein can improve the recovery process.

Read more: Does soy protein speed up recovery?

Final Recommendation – Is soy protein worth taking?

Overall, the evidence shows that soy protein is extremely beneficial. Soy protein has numerous health benefits including decreasing the risk of some cancers and heart disease. It can increase strength and muscle mass, decrease body fat, and improve the recovery process. Soy is just as capable as other, more popular, protein supplements.

Soy Protein Series

What is soy protein?

Does soy protein decrease testosterone levels?

What are the health benefits of soy protein?

Does soy protein increase strength?

Does soy protein improve cardio?

Does soy protein improve body composition?

Does soy protein speed up recovery?


  1. Hamilton-Reeves, J. M., Vazquez, G., Duval, S. J., & Phipps, W. R. (2010). Clinical studies show no effects of soy protein or isoflavones on reproductive hormones in men: Results of a meta-analysisFertility and Sterility, 94(3), 997-1007. doi:10.1016/j.fertnstert.2009.04.038
  2. Messina, M., Lynch, H., Dickinson, J. M., & Reed, K. E. (2018). No Difference Between the Effects of Supplementing With Soy Protein Versus Animal Protein on Gains in Muscle Mass and Strength in Response to Resistance ExerciseInternational Journal of Sport Nutrition and Exercise Metabolism28(6), 674–685. doi: 10.1123/ijsnem.2018-0071