Soy vs. Whey Protein

Is soy or whey protein better for athletes? STACK Expert Chris Costa examines some research and weighs in with his opinion.

Protein powder

Whey protein has ruled protein supplementation for years. But recent changes in how protein is processed have made soy protein a viable alternative. Still, many meat eaters turn their noses up at it, believing phytoproteins—or plant proteins—don't do the job like egg, milk, and beef protein.

A 2009 study in the Journal of Applied Physiology compared the benefits of whey, casein, and soy protein. Whey provided the quickest and most sustainable source of nutrient-rich amino acids for the muscles. But soy turned out to be an effective alternative if you experience gastrointestinal distress from milk.

It's great to get a fast-acting protein compound in your system, but it's also important to get ample amounts of protein throughout the muscle recovery process. A 2013 study in the Journal of Nutrition highlights the importance of prolonged levels of elevated amino acid concentration in the blood. It found that whey by itself enters the system extremely fast, but its effects do not last long.

A blend of whey and soy provides a smaller dose of amino acids initially, but delivers higher levels over a period of time, higher than whey alone. It's important to produce a sustained concentration of amino acids in the blood. It takes time for muscles to heal, especially when building-block branched-chain-amino-acids aren't available.

But soy also has drawbacks. It contains a compound called genistein, which can mimic the effects of estrogen. Could that be bad for men? Possibly. A study performed on fetal rats showed that excessive amounts of genistein inhibited testosterone-producing cells and could suppress the male sexual reproductive system.

Genistein is present in soy in only small amounts, but the risk may be a personal concern.

The research verdict is still out, but given soy's issues with estrogen and not packing as much of a protein punch, I recommend whey over soy protein for the time being.

Ed. Note: STACK Expert Mike T. Nelson also recommends whey protein over soy. Learn more about different types of protein via our Protein page.

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