Resistance-training athletes are constantly researching strategies to increase muscle mass, muscle size, strength, and power. Research has shown that protein consumption after resistance exercise is critical for stimulating muscle building and enhancing muscle recovery. But which type of protein powder is best for muscle growth? A recent study looked at the effects of soy vs. whey protein supplementation on hormonal responses following resistance training exercise. Ten resistance-trained young men took part in 3 experimental treatment conditions supplementing either 20g of whey protein, soy protein, or a maltodextrin placebo for 14 days. The subjects performed a heavy resistance exercise test following supplementation. The researchers found that supplementing with soy protein for 14 days lowered testosterone responses, while whey protein supplementation blunted cortisol responses during recovery. Cortisol not only weakens the activity of the immune system but also decreases amino acid uptake by the muscle, inhibiting the muscle building process.
Soy protein isolate has shown to be the highest quality plant-based protein source. Many vegan athletes supplement with soy as an alternative to animal and dairy based protein sources. However, many athletes are concerned with the possible hormonal or anti-growth affects of soy protein. Isoflavones, naturally occurring substances found in soy, possess estrogen like activities and are referred to as phytoestrogens. Previous evidence has shown the ability of soy to alter hormones such as testosterone, which promotes growth signals that are important for muscle building.
Evidence has shown animal and diary protein sources to be of the highest quality when it comes to digestibility and muscle building. Whey protein in particular, is a fast absorbing protein and contains high amounts of essential amino acids, including branched-chain amino acids (50% more than soy protein), which are crucial for the stimulation of muscle building and recovery. We agree with the findings of this study as previous evidence has shown that whey protein promotes greater muscle building when compared to soy protein. If you are interested in building muscle, take 20-25 g of whey protein along with water and fresh or frozen fruits (i.e. berries, bananas, etc.) after exercise.
Original research article can be found at Taylor & Francis Online
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