Soy Protein Isolate Defined


Soybeans and soy-derived protein products are complete vegetarian protein sources. Like animal protein sources, they provide all of the essential amino acids. In addition to being a high-quality protein source, soy protein isolate offers additional health benefits.


Soy protein is derived from defatted soy beans. There are many forms of soy protein products, and in terms of protein powders, there is soy protein concentrate and soy protein isolate. Soy protein isolate is the most pure and refined form of soy protein available. Whereas concentrate contains some carbohydrates and has a bean flavor, isolate is neutral-flavored, as most of the carbohydrates are removed and only the dried protein component is left. Soy protein isolate is often used as a protein powder supplement.

Protein Quality

Soy protein isolate is a very high-quality protein. Like whey and egg proteins, it has a perfect score of 1.0 on the “Protein Digestibility and Amino Acid Score” ranking, which is a measure of protein quality as well as the body’s ability to digest and utilize the protein source. It is the best substitute for animal-derived proteins and thus an optimal choice for vegans (people who do not consume any animal products).

Best Soy Isolate Supplement

Genisoy Ultra XT protein powder is made with soy protein isolate and recommended by The soy protein in this supplement is water-processed and retains healthy compounds, known as isoflavones (genistein and daidzein). The benefits of adding soy isoflavones to your diet is inconclusive, but might help reduce your risk of developing certain diseases. One scoop of Genisoy’s Soy Ultra XT Natural Protein Powder has 130 calories, 25g protein, 1.5g fat, 5g carbohydrates (0g sugar) and 4g dietary fiber. Fiber-rich foods might reduce blood cholesterol levels, particularly LDL (bad) cholesterol, according to the Dietary Guidelines for Americans.

Cholesterol Benefits

According to the Food and Drug Administration, soy protein is linked to a lower risk of heart disease. The FDA reviewed 27 research studies and concluded that soy protein lowers cholesterol levels of LDL (bad) cholesterol but leaves HDL (good) cholesterol levels intact. In a study published in the “Journal of Nutrition” in September 2009, researchers found that soy protein isolate consumption reduced serum LDL cholesterol (when compared to milk protein isolate) in patients with type 2 diabetes. The data suggests that consumption of soy protein has a beneficial effect on blood lipid levels, reducing the risk of cardiovascular disease in adults with type 2 diabetes.

Soy Versus Whey

Whey protein isolate is generally considered the gold standard in protein supplementation. While both have a perfect amino acid score and nearly identical digestability scores (thus similar PDCAA scores), whey protein isolate has a higher biological value than soy protein isolate, thus is better absorbed by the body. Per serving it offers a higher amount of essential amino acids; however, soy protein isolate offers more glutamine and arginine (two non-essential amino acids). Glutamine is important for muscle cell volume and growth and arginine promotes optimum blood flow and growth. While whey is clearly ahead overall, there are benefits to consuming soy protein isolate.

About this Author

Michele Turcotte is a registered, licensed dietitian, and a certified personal trainer with the National Academy of Sports Medicine. She has more than 12 years of experience in clinical and corporate settings, and has extensive experience in one-on-one diet counseling and meal planning. She has written freelance food and nutrition articles for Trouve Publishing Inc. since 2004.