Nothing fires me up more than leading the charge against the massive amounts of bullshit in the nutritional world. Luckily, Power Athlete has been in the business of battling bullshit for years. Today’s topic, soy. Often touted as a “miracle health food”, discover the link between soy and performance and how it could not only be working against you in the gym but also destroying your health.

What is Soy?

Soy is a legume which is a type of plant, such as a pea or bean, with seeds that grow in long cases called pods. Soy can now be found not only in the obvious foods (soy sauce, tofu, edamame), but can even be found hidden in things like canned tuna, prepared meat (such as pre-made burger patties) and even vitamins.

It still blows my mind that we’re continuing to have the soy argument. I assume we can blame most of it on the fact that the soy industry spends millions of dollars marketing it as the “healthy alternative” to meat or dairy with less fat and less cholesterol.(1) Or, maybe it’s because the media has decided that skinny jeans is an acceptable look for guys and they don’t care that continuing to sip their soy lattes is dropping their T levels faster than Beiber is selling records. Regardless, it’s our job to set the record straight. Soy isn’t and never has been part of the Power Athlete diet and is doing more damage to your potential gains than your high school sport coach.

SOY: Chemical Breakdown

My biggest beef with soy lies in its chemical structure. You see, soy contains phyto-estrogens, sometimes known in the literature as bioestrogens. These phytoestrogens chemically look very similar in the body as our own natural estrogen compounds and thus can disrupt our normal hormonal processes.

A recent study out of the University of Connecticut (2) looked at changes in estradiol concentrations in men utilizing either soy or whey supplementation following resistance exercise. After only 14 days, the men drinking soy were found to have lower testosterone levels and higher cortisol levels. That right there is a recipe for disaster if building muscle and increasing performance is your goal, but hard-charging athletes are not the only ones that should be worried about these results. Cortisol is a catabolic steroidal hormone that affects muscle tissue balance by increasing protein breakdown and decreasing protein synthesis.(3) Chronic elevation of cortisol can also lead to things like poor sleep and blood sugar dysregulation which in turn can result in unwanted weight gain and nobody wants that!

But phytoestrogens aren’t the only disturbing chemical compound in soy.

The soybean has one of the highest phytate levels of any grain or legume that has been studied. Grain or legume-based diets high in phytates can actually block the absorption of minerals such as calcium, magnesium, copper and zinc in the small intestines. The deleterious effects of magnesium deficiency in the Power Athlete was a recent topic of @John’s over at TTMJ. An article in the American Society for Clinical Nutrition pointed out that phytic acid was also a major inhibitor of iron absorption in soy-protein isolates.(4)  Anemia is a common problem we often see in female athletes. In fact, a 2011 study of female collegiate rowers in New York state found that 10% were anemic and 30% had low iron stores.(5) These low iron levels can contribute to fatigue, depression and most definitely poor performance.

Soy: Effect on Male Athletes

If someday producing a brood of mini Power Athletes is in your future, stepping away from the soy is even more important. Men in the highest category of soy food intake had an average 41 million less sperm/mL than men who did not consume soy foods.(6) A similar study found that an endocrine disrupting compound in soy called genistein can impair sperm as it swims towards the egg and even more surprising was that it took smaller doses of genistein to cause infertility in women than in mice.(7)

Soy and Performance

We’ve learned so far that research has demonstrated soy as an endocrine disruptor, cortisol driver, and mineral absorption inhibitor, but it’s also a piss-poor protein with regards to recovery. Regardless if you are trying to lay thick slabs of muscle, recover from your spin class or train for a 5k fun run, your body is going to need quality protein.  A study from the Journal of Applied physiology compared ingestion of whey hydrolysate, caseine, or soy protein isolate on the effects of protein synthesis. It was found that ingestion of whey protein resulted in a larger increase in blood essential amino acid, branched chain amino acid, and leucine concentrations than either casein or soy. Mixed muscle protein synthesis was 93% higher with whey than caseine and 18% higher with whey than soy.(8) 

Soy Users Are Losers

Taken together, I’d like to think we have successfully slain the soybean. It doesn’t matter if you’re a hard charging athlete looking to achieve pinnacle performance, or the person in the “masters” division trying to stay healthy, soy is NOT your friend and there is a definite negative link between soy and performance. We use our food to fuel the fire in the machine and what we eat affects very important aspects of life. If you’re leaving this article more confused than informed, then you are on your first step to enlightenment! Don’t give up, go down the wormhole. It will literally save you and your family’s life. If you don’t have time for that, head on over to our Power Athlete Nutrition programs. Here, you will find a nutrition plan that’s sure to fit YOUR goals!

1 Fallon, S. (2005, August). The Promotion of Soy – Weston A Price. Retrieved April 08, 2016, from http://www.westonaprice.org/health-topics/the-promotion-of-soy/

2 Kraemer WJ, Solomon-Hill G, et al.  The effects of soy and whey protein supplementation on acute hormonal responses to resistance exercise in men.   J Am Coll Nutr, 2013;32(1):66-74.

3 Garrett RH, Grisham CM. Biochemistry, 2nd Ed. Orlando, FL: Saunders College Publishing; 1999.

4 R F Hurrell, M A Juillerat, M B Reddy, S R Lynch, S A Dassenko, and J D Cook. Soy Protein, Phytates and Iron Absorption in Humans. American Journal of Clinical Nutrition, 1992; 56(3):573-578.

5 DellValle DM, Haas JD. Impact of iron depletion without anemia on performance in trained endurance athletes at the beginning of a training season: a study of female collegiate rowers. Int J Sport Nutr Exerc Metab. 2011 Dec; 21(6):501-6.

6 Chavarro JE, Toth TL, Sadio SM, Hausser R. Soy food and isoflavone intake in relation to semen quality parameters among men from an infertility clinic. Human Repr. 2008 23(11): 2584-2590.

7  Mercola, J. (2009, July 9). Eating Soy Can Decrease Your Fertility 7/9/05. Retrieved April 08, 2016, from http://articles.mercola.com/sites/articles/archive/2005/07/09/soy-fertility.aspx

8 Tang JE, Moore DR, Kujbida GW, Tarnapolski MA, Phillips SM. Ingestion of whey hydrolysate, caseine, or soy protein isolate: effects on mixed muscle protein synthesis at rest and following resistance exercise in young men. Journal of Applied Physiology. 2009 Sept; 107(3)987-992.

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