Does soy protein make you stronger?

Soy Protein and Strength

One of protein’s many important roles is repairing muscle tissue after a strenuous workout. This repair process is what makes us bigger, faster, stronger, and all around better athletes. The amount and source of protein intake is a hotly debated subject; it pits animal sourced protein supplements such as whey, casein, milk, and beef proteins against vegetable sourced options such as soy.

For a long time, animal sourced protein supplements have been seen as superior to plant based ones. With an increased focused on health, plant proteins are getting a second look. There is plenty of research showing the health benefits of replacing animal proteins with plant options. Even so, many are worried about the possibility plant proteins decrease performance.

Meta-Analysis: No Difference Between the Effects of Supplementing With Soy Protein Versus Animal Protein on Gains in Muscle Mass and Strength in Response to Resistance Exercise¹

This meta-analysis compared the effects of soy protein and animal protein on both strength and lean body mass. The review looked at nine studies and included 266 participants. Of the nine studies included, soy was compared to whey in five studies. It was compared to beef, dairy, or milk protein in the remaining four studies.

In the soy versus whey studies, there were significant increases in strength in both protein groups. Researchers did not see a difference in increases between the whey and soy groups.

Similarly, in the soy vs beef/dairy/milk protein studies, there were also significant increases in strength in both groups. There were no differences in increases between the various protein groups.

The authors of this meta-analysis point out that there is some research showing that whey protein is superior than soy in increasing muscle protein synthesis, and by extension, strength and size gains. Many researchers speculate higher leucine (one of the branched chain amino acids) in animal proteins is responsible for increased protein synthesis.

The authors of this review concluded that the totality of evidence suggests that soy foods and soy protein supplements are suitable for increasing strength and muscle mass when used in conjunction with a resistance training routine. They state that the results of the nine studies indicate the protein source is not the most important factor that influences strength and size gains.

Other Soy vs Animal Protein Studies

Effect of whey and soy protein supplementation combined with resistance training in young adults²

Conclusion: Protein supplementation, regardless of source, resulted in similar strength gains.

Ingestion of whey hydrolysate, casein, or soy protein isolate: effects on mixed muscle protein synthesis at rest and following resistance exercise in young men³

This study looked at the effects of various proteins on rates of muscle protein synthesis.

Conclusion: Whey protein increased protein synthesis to a greater degree than casein protein. Whey and soy protein increased protein synthesis to similar rates.

The Bottom Line – Recommendations on Using Soy Protein to Increase Strength

The meta-analysis and studies covered here show soy protein is just as capable as whey protein at increasing strength and muscle protein synthesis. Soy protein’s ability to improve strength combined with its many health benefits make it a great alternative for those looking to reduce consumption of animal products.