Ask the Coach: Soy or Whey?

John asks: I’m looking at doing a vegan diet this lent and it is in the middle of my training period for St. George Ironman.  In reviewing Protein powders and shakes, I’m finding that soy based protein powers are cheaper and pack more protein than whey based powders and shakes.  Is there some downside that I’m missing that would cause the popularity of whey based protein products instead of soy?

Let’s define a few things first. A vegan diet is a purely plant-based diet. Nothing that comes from animals is consumed. While some vegetarians might do eggs and/or dairy, a vegan diet is void of anything associated with animals. Because whey protein is derived from milk, it doesn’t fit into a vegan diet.

John will need to ensure adequate protein intake during ironman training to make sure his body can repair the damage to the muscles that happens during his training sessions. While this is possible to do with diet alone, it is more challenging on a vegan diet, due to a reduced selection of protein sources. This is where supplements can be convenient to use, especially to get that needed protein immediately after a workout.

Finding good information on supplements can be tough to navigate because a lot of the online information is from the supplement companies trying to sell their product. I sought the advice of a couple sports dietitians and got some research articles from them. I also took a look at some of the sports nutrition books I have. The bottom line is that while whey does have a better essential amino acid profile and biological value soy is an acceptable substitute. Proteins are rated as follows in terms of quality: whey, milk, casien, egg, soy, beef.¹

If protein (whey or soy) is consumed immediately after a workout to aid in muscle rebuilding, whey might be your “purest” source but soy will do the job as well. Any protein is better than no protein! Soy protein has a unique flavor and texture, and isn’t quite as soluble as whey, which often turns people away from it. But if you are trying to stay vegan, as John is considering, there is nothing wrong with consuming soy protein.

For a more thorough comparison of whey vs. soy and other proteins, read this Hammer Nutrition article.

¹Seebohar, Bob. Nutrition Periodization for Athletes, 2nd Ed. Bull Publishing. 2011. p. 49.