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The Muscle-Building Joy of Soy

Soy protein has been around since about the time Jesse Owens was kicking some major German ass in Berlin, at the ’36 Olympic Games. Yes, indeed, a long time. When I think of soy, edamame comes to mind. I’m not really a heavy soy consumer, but then again, I don’t drink milk either. That said, what’s the data on soy? It may not be as good as whey protein, but then again, what protein is?

The data on soy is actually quite intriguing. Recently, scientists determined the influence of soy protein intake and weight training on resting energy expenditure in postmenopausal women. The 160-week study divided women into four groups: G1, soy protein plus exercise; G2, placebo plus exercise; G3, soy protein and no exercise; and G4, placebo and no exercise. The subjects got 25 grams of soy per day, and the exercisers performed a standard weight-training regimen.

Significant increases in metabolic rate—i.e., resting energy expenditure—were detected in G1 (158 kcal/day, 17 percent) and G2 (110 kcal/day, 9 percent), whereas a 4 percent decrease was detected in G4. Thus, soy protein coupled with weight training can further boost metabolism.1

Another study compared soy vs. whey protein bars. Scientists measured lean body mass in men enrolled in a college weight-training class who were given soy or whey protein bars (33 grams of protein per day) for nine weeks. Both protein groups showed a gain in lean body mass, but the training-only group did not. What’s interesting and rather odd is that the whey and training-only groups showed a potentially harmful posttraining effect on two antioxidant-related parameters, but the soy group did not. So in essence, both bars promoted a lean-body-mass gain, but the soy had the added antioxidant benefits.2

In fact, another study found that soy protein, but not milk protein, supplementation improves the lipid profile of healthy adults.3 Furthermore, muscle protein synthesis was not different between casein, a milk protein and soy.4

So the moral of the story is that soy can help build lean body mass and give you some health benefits to boot!

Editor’s note: Jose Antonio, Ph.D., is the CEO of the International Society of Sports Nutrition (; also check out his site


1 Trevisan, M.C., et al. (2010). Influence of soy protein intake and weight training on the resting energy expenditure of postmenopausal women. Rev Assoc Med Bras. 56(5):572-8.

2 Brown, E.C., et al. (2004). Soy versus whey protein bars: effects on exercise training impact on lean body mass and antioxidant status. Nutr J. 3:22.

3 Wofford, M.R., et al. (2001). Effect of soy and milk protein supplementation on serum lipid levels: a randomized controlled trial. Eur J Clin Nutr. In press.

4 Luiking, Y.C., et al. (2011). Differential metabolic effects of casein and soy protein meals on skeletal muscle in healthy volunteers. Clin Nutr. 30(1):65-72.


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