Soy Vs. Whey

Soy Vs. Whey

Why do you work out?  If you're like most people your reason is likely to feel better, enhance your physique by building lean muscle and losing fat, and/or to improve your health.  These processes require a number of factors to be in order and a primary component is your diet, which many people feel is by far the most important component. 

To put it one way, having a "perfect" workout day is far easier as you can shown up to the gym and train your tail off, but a "perfect" nutrition day goes from sun up to sun down -- every day!  Building muscle and burning fat demands intense, consistent workouts along with a killer diet, plus enough healthy calories to facilitate muscle growth (but not too much or you will build fat). increasing protein intake is one of the best strategies to accomplish this needed balance.

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Not All Proteins Are Created Equal
Can you increase your protein intake to levels you need to build muscle and still support and even improve your health?  This too can be a tricky balance and in this regard, this is where the source of your protein can become important.  How many different sources of protein can you think of?  Beef, bison, chicken, turkey, milk, soy and many plants have some protein in them as well.  While a protein source like beef can range a great deal in the amount of protein, fat and cholesterol they contain, other protein sources like milk proteins (whey in particular) and soy offer excellent health benefits, but the extent to which they support your workout goals can vary widely.

Soy protein, in fact, is considered by many to be one of the more healthy proteins.  The components found within soy are isoflavones that contain naturally occurring nonsteroidal substances called phytoestrogens.  Phytoestrogens interact with the estrogen receptor on the muscle membrane and increasing your intake of soy-based products naturally increases your intake of phytoestrogens which may result in decreased incidence of coronary heart disease and different cancers (Erdman and Fordyce 1989, Montgomery 2003).  Isoflavone and phytoestrogen intake may also improve risk for osteoporosis, reduce triglycerides as well total and LDL cholesterol (Wong, Smith et al. 1998, Teede, Dalais et al. 2001) and can be a key part of a successful weight management program (Bhathena and Velasquez 2002).

Soy Protein and Hormonal Response
The health benefits of soy are well established, but speculation remains whether regular ingestion of soy protein is ideal for resistance training males who seek to maximize various hormonal responses in an effort to get stronger and increase their muscle mass.  In fact, a good amount of scientific evidence exists to support both sides of the argument and fortunately, a recent study published in the Journal of the American College of Nutrition sheds some light on this exact topic. 

The purpose of this study by researchers at the University of Connecticut was to examine the extent to which soy and whey protein impacted changes in various hormones in response to a single bout of heavy lower-body resistance training (Kraemer, Solomon-Hill et al. 2013).  The authors had ten college-age resistance-trained men perform three identical experimental trials.  Each trial was separated by a 14-day period called a washout period.  Each trial began with a 14-day supplementation period where participants consumed either 20 grams of a carbohydrate placebo, 20 grams of soy protein isolate or 20 grams of whey protein isolate each morning during the supplementation period. 

After the supplementation period, participants performed a single bout of lower body resistance training by completing 6 sets of 10 repetitions at approximately 80% of each study participant's one-repetition maximum (1RM).  A series of seven blood samples were collected before and within the first hour after completing the exercise bout to measure changes in key hormones such as testosterone, cortisol and estrogen.

The authors found that when soy protein was provided, serum levels of testosterone were diminished and cortisol levels (a stress hormone) were greater when compared to the levels measured when whey protein was consumed.  When both testosterone and cortisol were observed together, 20 grams of whey protein supplementation promoted and sustained higher levels of testosterone while also causing the lowest levels of cortisol (Kraemer, Solomon-Hill et al. 2013).  The authors concluded that supplementation with whey protein led to the most favorable changes in hormones found in the blood in response to a single bout of resistance training and in particular that ingestion of soy blunted increases in testosterone and increased levels of cortisol.  Other studies exist to demonstrate that using soy protein can negatively impact levels of key hormones such as testosterone (Gardner-Thorpe, O'Hagen et al. 2003), sex hormone binding globulin (Habito, Montalto et al. 2000) as well as the ratio between testosterone and estrogen (Habito, Montalto et al. 2000).  Moreover, it is thought that soy may inhibit the function of some key enzymes that facilitate the production of various androgens (Evans, Griffiths et al. 1995, Makela, Poutanen et al. 1998).

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Whey Protein Generates a
Preferable Hormonal Response

Whey protein, particularly high quality hydrolyzed isolate versions such as BioQuest's MyoZene and ProSource's NytroWhey Ultra Elite possess extremely favorable profiles of amino acids and in particular contain the highest concentrations of the essential amino acids as well as the branched-chain amino acids.  As mentioned before, a recent study reported that when similar amounts of protein were given prior to completing an intense bout of lower-body resistance training, the most favorable changes in both testosterone and cortisol were found when a whey protein isolate was given (Kraemer, Solomon-Hill et al. 2013). 

Isolate versions of whey protein like those found in MyoZene and the entire NytroWhey family are the purest forms of whey protein and as a result contain the highest amounts of protein, essential amino acids and branched-chain amino acids (the good stuff) and the lowest amounts of fat and carbohydrate (the bad stuff).

Whey Protein Ingestion Supports
Increased Protein Synthesis

Hormone response is important, but there are other factors in play as well. Two recent studies compared the impact of soy and whey protein on changes in muscle protein synthesis at rest as well as after resistance exercise.  The first study had young college-aged men complete three experimental trials where during each visit they ingested similar amounts of either whey, casein or soy protein.  Muscle protein synthesis was measured both at rest and after a single bout of resistance exercise.  At rest, rates of muscle protein synthesis after whey protein ingestion were 18% greater than when soy protein was ingested.  When the same response was measured after completing a single bout of heavy resistance exercise, the results favored whey protein even more, leading to 31% higher values of muscle protein synthesis (Tang, Moore et al. 2009).  

Think these results only apply to young men?  Think again!  These results were reported again in a later study which used older men whereby whey protein ingestion resulted in greater levels of muscle protein synthesis when compared to soy protein ingestion (Yang, Breen et al. 2012, Yang, Churchward-Venne et al. 2012).

In conclusion, soy protein, particularly isolate versions, are considered to be high quality sources of protein, but a number of studies continue to provide evidence that soy protein ingestion might lead to unfavorable changes in key hormones that are a part of the muscle building process.  On the other hand, high quality, isolate versions of whey protein like those found in MyoZene and the NytroWhey Ultra Elite have the highest levels of amino acids and when compared head to head, and a number of studies indicate that whey protein ingestion promotes greater increases in muscle-building processes.

Do you take a soy protein supplement? What have your results been with it? Let us know in the comments field below!


Bhathena, S. J. and M. T. Velasquez (2002). "Beneficial role of dietary phytoestrogens in obesity and diabetes." Am J Clin Nutr 76(6): 1191-1201.

Erdman, J. W., Jr. and E. J. Fordyce (1989). "Soy products and the human diet." Am J Clin Nutr 49(5): 725-737.

Evans, B. A., K. Griffiths and M. S. Morton (1995). "Inhibition of 5 alpha-reductase in genital skin fibroblasts and prostate tissue by dietary lignans and isoflavonoids." J Endocrinol 147(2): 295-302.

Gardner-Thorpe, D., C. O'Hagen, I. Young and S. J. Lewis (2003). "Dietary supplements of soya flour lower serum testosterone concentrations and improve markers of oxidative stress in men." Eur J Clin Nutr 57(1): 100-106.

Habito, R. C., J. Montalto, E. Leslie and M. J. Ball (2000). "Effects of replacing meat with soyabean in the diet on sex hormone concentrations in healthy adult males." Br J Nutr 84(4): 557-563.

Kraemer, W. J., G. Solomon-Hill, B. M. Volk, B. R. Kupchak, D. P. Looney, C. Dunn-Lewis, B. A. Comstock, T. K. Szivak, D. R. Hooper, S. D. Flanagan, C. M. Maresh and J. S. Volek (2013). "The effects of soy and whey protein supplementation on acute hormonal reponses to resistance exercise in men." J Am Coll Nutr 32(1): 66-74.

Makela, S., M. Poutanen, M. L. Kostian, N. Lehtimaki, L. Strauss, R. Santti and R. Vihko (1998). "Inhibition of 17beta-hydroxysteroid oxidoreductase by flavonoids in breast and prostate cancer cells." Proc Soc Exp Biol Med 217(3): 310-316.

Montgomery, K. S. (2003). "Soy protein." J Perinat Educ 12(3): 42-45.

Tang, J. E., D. R. Moore, G. W. Kujbida, M. A. Tarnopolsky and S. M. Phillips (2009). "Ingestion of whey hydrolysate, casein, or soy protein isolate: effects on mixed muscle protein synthesis at rest and following resistance exercise in young men." J Appl Physiol 107(3): 987-992.

Teede, H. J., F. S. Dalais, D. Kotsopoulos, Y. L. Liang, S. Davis and B. P. McGrath (2001). "Dietary soy has both beneficial and potentially adverse cardiovascular effects: a placebo-controlled study in men and postmenopausal women." J Clin Endocrinol Metab 86(7): 3053-3060.

Wong, W. W., E. O. Smith, J. E. Stuff, D. L. Hachey, W. C. Heird and H. J. Pownell (1998). "Cholesterol-lowering effect of soy protein in normocholesterolemic and hypercholesterolemic men." Am J Clin Nutr 68(6 Suppl): 1385S-1389S.

Yang, Y., L. Breen, N. A. Burd, A. J. Hector, T. A. Churchward-Venne, A. R. Josse, M. A. Tarnopolsky and S. M. Phillips (2012). "Resistance exercise enhances myofibrillar protein synthesis with graded intakes of whey protein in older men." The British journal of nutrition: 1-9.

Yang, Y., T. A. Churchward-Venne, N. A. Burd, L. Breen, M. A. Tarnopolsky and S. M. Phillips (2012). "Myofibrillar protein synthesis following ingestion of soy protein isolate at rest and after resistance exercise in elderly men." Nutr Metab (Lond) 9(1): 57.

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