Difference Between Whey & Soy Protein

Two of the most common protein supplements, whey and soy, contain essential amino acids, so they are considered "complete" proteins. Whey protein comes from the cheese-making process, while soy protein comes from soybeans, which are primarily cultivated in the Americas and Asia. While you're more likely to consume whey protein as a dietary supplement, you can find soy products such as tofu, soy milk or tempeh at your grocery store.

Origin

Remember Little Miss Muffet, eating her curds and whey? When cheese-makers turn cow's milk into cheese, they separate liquid whey from the casein, which forms the curd. Eventually producers break up the liquefied whey into different components, including whey protein, which they then concentrate, dry and purify. Soy plants, on the other hand, produce soybeans, which can be ground into flour and defatted. The United States, Brazil, Argentina, China and India produce the most soybeans, according to Soyatech, a soybean research and consulting firm.

Composition

Both whey and soy protein are available as isolates or concentrates. Whey and soy protein isolate contain about 90 percent protein. Whey protein concentrate contains between 30 and 90 percent protein, according to the Whey Protein Institute. Carbohydrate-free soy protein concentrate, meanwhile, is about 70 percent protein. Textured soy protein, a popular meat substitute, comes from concentrated soy.

Benefits

Both whey and soy protein contain essential and branched-chain amino acids, which can improve muscle mass and strength. Because your body quickly absorbs whey protein, many weight-lifters consume it after workouts when their bodies most need to recover. An 2003 analysis led by Kristen Montgomery that was published in the "Journal of Perinatal Education" claims soy protein can reduce cholesterol levels and symptoms of menopause. Soy and whey protein may prevent cardiovascular disease, diabetes and cancer, but this research, however, is very preliminary.

Consumption

Many sports and nutritional supplement makers sell either protein type as powders or bars. Manufacturers often combine them with carbohydrates, vitamins or other "performance-enhancing" ingredients. You can add whey and soy protein to smoothies and shakes. Unlike whey protein, soy protein is commonly found in everyday food items, including cereal bars, tofu, soy milk and meat-replacements.

Considerations

In reasonable amounts, both whey and soy protein are generally safe. If you are allergic to dairy, you may be allergic to whey protein. Some experts warn against soy supplementation, especially for men, because it contains estrogen-like isoflavones. These phytoestrogens could pose problems for women, too, if they are pregnant or at-risk for breast or ovarian cancer.