Whey, Soy, or Casein Protein: Which is best for Athletic Performance?

Posted by Shelley Harper on Nov 4, 2013 4:42:00 AM

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The first time I heard soy or whey protein, I was ordering a protein boost in my Jamba Juice. I nervously gave my friend next to me a “What did she just ask?”-type smile and just ordered soy to pretend I knew what I was doing. I might have known nothing then, but here we are, ten years later, and I’m ready to demystify these various protein sources for you. In this article, I’ll share the facts on soy, whey and casein proteins to help you maximize your strength training.


  • Whey Protein is an animal based protein originating from cow’s milk. It is a “complete”
    protein, meaning it contains all nine of the essential amino acids that our bodies do not produce naturally. (We produce the other 11 amino acids).
  • Soy Protein is a plant-based protein originating from the soybean plant. Soy protein is a complete protein, like whey, and is one of the only non-animal based proteins that is “complete”. Soy is a great protein source for vegan or lactose intolerant individuals.
  • Casein Protein, like whey, is a milk-based protein. It makes up 80% of the protein in cow’s milk, making it more abundant that whey. It is also a complete protein.


It is widely known that protein is vital in the development of lean body mass, but important questions still linger. What protein source is the best for athletes? Can the timing of protein consumption affect muscle building? In what foods and supplements can an athlete find specific protein types? Let’s tackle these questions below:


What protein source is best for athletes?

In a study on male athletes, the effects of soy and whey protein consumption on building muscle mass were compared. Results found that both whey and soy consumption increased muscle mass when combined with exercise training. It also concluded that there was no significant difference in muscle mass gains between the two protein sources. This disproves the pre-conceived notion that whey is a better protein source to increase one’s lean body mass than soy. In fact, this study also showed that, in addition to increasing muscle mass, soy protein provides important antioxidants not provided by whey. So, while both whey and soy protein increase muscle mass when paired with exercise, soy protein has the added benefit of containing antioxidants, but this is far from the end of the debate.When determining the best protein source for athletes, it is also essential to consider the protein’s absorption rate. This moves us on to our next question:



Can the timing of protein consumption affect the repairing and building of muscles?

Sources say…Yes! If fact, whey protein is found to have the fastest absorption rate among all proteins. This knowledge can be used in strategically developing a post-workout fueling plan as the fast absorption of whey protein allows for the quick rebuilding of muscles after consumption. This characteristic makes whey protein great for both pre-workout fuel (the protein can be utilized quickly) and post-workout recovery (to rebuild the muscles that were just broken down). On the other hand, soy protein has an intermediate absorption rate, which makes it less effective in immediately rebuilding muscle; however, it is vital in the building of new muscles tissue. Lastly casein protein has the slowest absorption rate but in doing so it elevates plasma amino acid levels for the longest period of time. These free amino acids can be used to build muscle hours after exercise. Each of these protein sources provides different benefits, and incorporating all three into a nutrition plan will kickstart muscle synthesis immediately after exercise and maintain it for several hours


In what foods and supplements can I find each type of protein?

Common food sources of soy protein include edamame and tofu. Soy protein can also be found in powder that you can add to smoothies or sprinkle in your cereal. There are also many varieties of soy milk, cheese and yogurt. A small amount of whey protein is naturally found in milk, cheese and yogurt, but is most commonly marketed in protein powders, shakes and other dietary supplements. This allows for a greater whey protein content than you will receive in natural foods. A few commonly known brands that sell products with whey protein include Muscle Milk, Gatorade and EAS Sports Nutrition. Lastly casein protein is found in milk and makes up 80% of the protein in milk sources. Casein protein can also be found in powders aswith soy and whey.

Below is a quick summary of the protein comparison:


Whey Protein

  • Animal source
  • Fast-absorbing
  • Ideal for repairing broken down muscles
  • Great for pre-workout fuel and immediate post-workout replenishing

Soy Protein

  • Plant source
  • Ideal for lactose intolerance athletes
  • Intermediate absorption rate
  • Ideal in the formation of new muscle mass
  • Also provides anti-oxidative benefits


Casein Protein

  • Animal source (makes up 80% of protein in cow’s milk)
  • Slow absorption rate
  • Great for prolonging muscle synthesis hours after exercise


Lastly, I want to end by saying that it is important to find a nutrition regimen that works for YOU! While whey protein might be the best option for your lifting partner, if it upsets your stomach, listen to your own body to make educated nutrition decisions. Remember that protein supplements can help your athletic performance, but it is your hard work in the weight room and at practice that will ensure your development and allow you to reach that goal you have been training for.


1. Brown, Erin et al. (2004) Soy versus whey protein bars: Effects on exercise training impact on lean body mass and antioxidant status. Nutrition Journal 2004, 3:22

2. http://www.fitday.com/fitness-articles/fitness/body-building/which-is-best-soy-protein-or-whey.html

3. http://www.nutritionexpress.com/showarticle.aspx?articleid=787

4. http://www.precisionnutrition.com/whey-vs-casein

Topics: Nutrition