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Whey vs. soy: gain 7.3 pounds of muscle

Many studies have shown that whey protein rapidly increases muscle protein synthesis, and the effect is amplified when consumed before and/or after resistance exercise. However, it’s not always appropriate to extrapolate short-term data to draw long-term conclusions. So the question of whether consistent supplementation with whey protein translates into greater gains in muscle mass from resistance training remains unclear. 

My lab group at the University of Connecticut recently presented results of a large prospective study comparing whey protein to soy protein at the American College of Sports Medicine Annual Meeting. This study involved a 9-month resistance training and supplementation program with the main objective to examine changes in lean body mass determined by dual-energy X-ray absorptiometry (DXA).

A total of 147 healthy, untrained men and women completed baseline testing and then were randomly assigned in a double-blind manner to supplement daily with either whey protein, soy protein or carbs only (in individual packets of powder) while performing supervised resistance training. The supplements had similar caloric values. The whey and soy supplements contained equal amounts of protein. Subjects consumed the supplement in the morning with breakfast on non-training days and immediately after exercise on training days. The resistance training program consisted of supervised workouts 2-3 times per week.

The subjects were also prescribed a specific diet including a constant protein intake of 1g per kg of body weight (not including the additional supplementation). For the whey and soy protein groups, the addition of the daily protein supplement (22g per day) increased protein intake to 1.4g of protein per kg of body weight (about 95g of protein for a 150-pound person).  

We are currently analyzing a large number of variables, but preliminary results indicated that regular consumption of whey protein significantly increased plasma levels of leucine and BCAAs. Despite consuming similar calories and protein during the program, gains in lean body mass were significantly greater in the whey protein group (7.3 pounds) than the soy protein group (3.9 pounds). This is the largest and longest resistance training study comparing the effects of protein sources on gains in lean body mass. The results give an edge to whey over soy protein in this group of young, healthy men and women. 

 

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