Soy protein comes from dehulled and defatted soybeans. After collection, soy manufacturers produce three basic commercial products: soy concentrates, soy flour and soy isolates. In 1999, the Food and Drug Administration approved a health claim stating that 25 g of soy protein per day, together with low saturated fat and cholesterol diet, could reduce the risk of heart disease.
Soy Protein and PDCAAS
The Protein Digestibility Corrected Amino Acid Score is the official method of assessing protein quality. The World Health Organization, the FDA and the United States Department of Agriculture developed this scoring system. The highest score a protein can receive on the PDCAAS scale is 1, and 0 is the lowest score. Soy protein scores a 0.9 to 1.0 on the PDCAAS scale. According to the United Soybean Board, you can easily digest the majority of soy products, as indicated by the PDCAAS scale.
Soy Protein Nutrition Values
Soybean protein is a complete protein source because it contains all eight essential amino acids for human nutrition. Soy is also rich in fiber, iron, calcium, zinc and B vitamins. According to "Vegan for Life: Everything You Need to Know to Be Healthy and Fit on a Plant-Based Diet," soy can help child and adult vegans meet daily protein requirements. Further, soy protein is the only widely available complete source of vegetable protein.
Dietary Protein Quality of Soy
Dietary protein quality depends on the degree and speed your body digests, absorbs and retains the protein. One study published in the May 2005 "Journal of Nutrition" compared the metabolic effects of casein and soy proteins in healthy human subjects. The study found that subjects consuming soy protein had a lower protein synthesis than subjects that consumed casein protein meals. In other words, according to the study, your body does not digest and process soy as effectively as some other proteins, such as casein.
The Downside of Soy Protein
According to "The Whole Soy Story: The Dark Side of America's Favorite Health Food," soy is not a good digestible source of protein. In spite of having essential amino acids and important minerals, soy contains phytic acid, a substance known to block your body's absorption of minerals such as zinc, magnesium, calcium and iron. Soybeans also contain some substances known to inhibit some enzymes, such as trypsin, that your body requires for protein digestion. Therefore, although protein scores highly on the PDCAAS scale rating the quality of protein, some of the natural components of soy can inhibit your enzymes and prevent your body from absorbing some essential minerals. In other words, soy is an excellent source of protein, but soy can also indirectly cause health problems by exhibiting enzymes and preventing your body from absorbing some essential minerals.
References
- "The Whole Soy Story"; Kaayla T. Daniel; 2005
- "The Hidden Dangers of Soy"; Dianne Gregg; 2008
- "Vegan for Life: Everything You Need to Know to Be Healthy and Fit on a Plant-Based Diet"; Jack Norris, et al.; 2011
- "The Journal of Nutrition"; Casein and Soy Protein Meals Differentially Affect Whole-Body and Splanchnic Protein Metabolism in Healthy Humans; Yvette C. Luiking, et al.; May 2005
Member Comments