Soy As Good As Whey For Building Muscle

Soy protein is as effective as the bodybuilder's favorite, whey, in maintaining muscle mass after endurance training, according to a study in rats.

"Soy can be a healthy part of post-exercise nutritional support," Dr. Tracy G. Anthony of the Indiana University School of Medicine in Evansville, the study's lead author, told Reuters Health.

While the body's skeletal muscle protein-building rate slows after an endurance workout, it actually speeds up after resistance exercise, she noted in an interview. After either type of exercise, taking in protein helps accelerate protein synthesis.

Weight lifters and other athletes often use whey-packed supplements because they are easily digested and therefore theoretically help build muscle faster, Anthony and her colleagues note in their report. But they have been less interested in using soy, she noted in an interview.

"There is this thought that because it's a vegetable-based protein, soy protein would not be as effective as an animal protein," Anthony explained. Male athletes may also hesitate to use soy as they fear it may have a feminizing effect, she added.

Anthony and her colleagues compared the effect of feeding rats soy or whey protein in helping them to restore muscle mass after they were exercised for two hours on a treadmill. Animals were fed carbohydrates only, carbohydrates plus soy, or carbohydrates plus whey, and all three regimens were compared in exercise and non-exercised rats.

The Solae Company, which makes soy-based supplements, funded the study, which is published in the Journal of Nutrition.

The effect of whey and soy was similar, the researchers found. "In terms of muscle protein synthesis they were equally effective," Anthony said.

"This is nice that we've shown this effect immediately after exercise, because this is when most people take their supplements," she added.

In the same rat model, Anthony said, she and her colleagues had previously found that protein consumption after endurance exercise sped up protein synthesis, a finding that has since been confirmed in humans.