Soy, a plant in the pea family, has been grown in Asian countries for centuries as a food crop. It is the only vegetable food that contains all essential amino acids, making it a source of complete protein, as are meats, eggs and milk products. This makes soy a good protein source for vegetarians. Products made from soy beans include miso, tempeh, soy flour, soy milk and soy sausage. Bioactive chemicals in soy also provide health benefits. Before using any type of soy protein supplement, consult a medical doctor or a registered dietitian.
Soy Protein Components
Soy, on a dry weight basis, contains about 41 percent protein and 21 percent oil. It has the highest protein content among all cultivated crops. Soy also contains fiber and polyunsaturated fats, as well as vitamins and minerals, including folic acid, ascorbic acid, B vitamins, calcium and iron. Soybean oil, a pale yellow oil, is a significant source of two polyunsaturated fats, linoleic and linolenic acids, which may be important in promoting cardiovascular health and vascular function. The nonnutritive compounds in soy, especially isoflavones, have also important implications for reducing cancer risk.
Health Benefits
Soy protein has various proposed health benefits. For example, soy improves blood vessels' ability to dilate and contract and can reduce high blood pressure. Soy protein and its isoflavones have modest platelet adhesion inhibition effects, which may prevent stroke and myocardial infarction or heart attack. Scientists are not sure about estrogen's link with breast cancer. Ask your doctor to determine if soy is right for your condition.
Moderation is Key
Convincing evidence shows that soy protein intake has beneficial effects on human body, but the ideal sources or dose is still unknown. Soy in moderation is healthy and safe, but you should avoid supplements that contain only isolated soy isoflavones. In addition, whole foods rather than supplements are generally better because unprocessed foods beat single nutrients.
Safety Issues
Avoid all soy products if you're allergic to soy, including tofu, miso, soy milk, soy sprouts and soy flour. Soy protein contains allergens that can cause reactions or illnesses, which range from mild skin reactions to serious gastrointestinal disturbances, labored respiration, wheezing, dizziness, fainting and low blood pressure. Soy is a low thyroid food, so it is not safe to eat soy products if you have a thyroid condition.
References
- University of Maryland Medical Center; Soy; December 2009
- Ohio State University: Soybean Proteins
- Beth Israel Deaconess Medical Center: BIDMC Research Investigator/Faculty Information
- University of Southern California; So Far Soy Good; Alicia Di Rado
- University at Buffalo; Soy Isoflavones Decrease Risk of Invasive Breast Cancer, Large Breast Tumors, Study Shows; Anne Weaver; November 2010
- Cornell University; Sprecher Institute for Comparative Cancer Research; Phytoestrogens and Breast Cancer; July 2003
Member Comments