The Soy / Whey Testosterone Connection

This morning my attention was captured by an article in Muscle Magazine. The article reported the results of a study in the Journal of the American College of Nutrition in the comparison of Soy Protein, Whey Protein and Carbohydrate when used in resistance training and the responses of testosterone, sex hormone binding globulin, estradiol and cortisol levels in men. Some of the points in the article indicated that soy protein significantly lowers testosterone levels and that it also possibly blunts the anabolic response post workout.

I wanted to learn more, so I did another search on this. The next article I read was posted by Muscle & Body Magazine. It said, a new study indicates that soy protein works for bodybuilders and it does not appear to hinder anabolic signaling post exercise by means of eliciting increases in estradiol concentrations (does not produce estrogen).

So, I started laughing and decided to go right to the source for the information. Here’s what I found. William J. Kraemer conducted this study with 10 healthy men in their early 20’s. The test split them into three groups where they were given every morning 20 grams of either whey, soy or carbohydrate and then proceeded to do the same workout based on 6 sets of 10 reps of that subject’s 1 rep max (1RM). The test ran for 2 weeks followed by a 2 week “washout” period to make sure the ingredients were out of their system. Then, ingredients were switched up and administered for another 2 weeks followed by another 2 week washout and then a final 2 weeks of the third ingredient. Blood samples were taken and biochemically analyzed at specific points in time. These would be done: Pre workout, Mid workout, Immediately Post workout, then again 5, 15, 30 and 60 minutes post. The results concentrated on levels of Testosterone, Estradiol, Sex Hormone Binding Globulin and Cortisol. The most remarkable results in the test were in testosterone and cortisol levels. The following graphs indicate that Soy Protein may contribute to a significant decrease in testosterone levels post workout and Whey Protein may contribute to a significant decrease in Cortisol levels post workout. The change in Sex Hormone Binding Globulin and Estradiol in this test were negligible and thus unremarkable.

Cortisol graph

testosterone graph

So… What the heck does all this mean to us??? Well, higher testosterone levels would promote more muscle growth and cortisol (the stress hormone) is a hormone directly associated with gluconeogenesis. Gluconeogenesis is the new creation of glucose for energy. This is typically done where cortisol catabolizes or breaks down muscle tissue for energy. This is also known as wasting. To continue to build lean muscle mass, keeping testosterone levels up and cortisol levels down would be considered a good thing. So, in a nutshell… Whey protein still has my vote. The study indicates that whey has a very significant contribution in lowering cortisol levels.

Now, to be totally unbiased with this test, the truth is, there were only 10 test subjects of a certain age. They were only administered 20 grams of the test ingredient per day. The experiment ran for only 10 weeks (6 weeks with 4 weeks of rest) and no women were included in this study. So in all fairness, this was a good start but more variables need to be included for accuracy with different age groups and genders. So in the meantime, my motto is: When in doubt, leave it out! I hope this helps demystify some of the controversy surrounding these proteins and I’ll certainly keep you posted as more information becomes available.

Until we meet again… Love your life and live it without limits!

About the Author:

Michael Rorick is a Certified Personal Trainer at Springville Health and Fitness Center, Springville NY. He is also a Certified Fitness Nutrition Specialist with a Certification in Weight Management as well. His company, Alive Without Limits was founded through his passion for helping others to reach their potentials in all areas of life. At 51 years of age, he is an avid bodybuilder, musician, audio engineer, forensic audio expert, professor at SUNY at Fredonia, life coach and father.

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