As summer approaches and thoughts of slimming-down for swimwear season start, men (and women) may want to take note of a 2013 study in the Journal of the American College of Nutrition. It compared the effects of a pre-workout serving of whey protein isolate, soy protein isolate, or a placebo in resistance-trained males, prior to high-intensity weight training sessions. The study found that after two weeks, whey protein elicited less cortisol production than soy, while soy protein caused lower testosterone levels… (and remember testosterone is important for woman’s hormonal health too!)
This is a double-whammy for choosing whey protein isolate powder over soy protein when you are making your smoothies or workout shakes. Not only does the higher cortisol associated with soy breakdown muscle mass, and increase blood-sugar and tendency to store fat, if what you are seeking is greater muscle strength or size, then obviously you want more testosterone not less, i.e. whey not soy.
The reduced stress response from whey may easily be attributed to its high content of branched chain amino acids, which your muscles can directly burn for energy, or the ability of whey protein to increase glutathione, so important for energy and mitochondrial function, immune function, and liver detoxification.
So, as long as you are not intolerant to whey, this gives you many reasons to choose whey protein isolate over soy protein for improved energy and muscle mass. In fact, there’s ample reasons to choose many other types of protein over soy, which is virtually all genetically modified and heavily sprayed!
Cheers!
John