Soy contains a healthy source of dietary protein with all nine essential amino acids that your body cannot manufacture on its own and must obtain from outside food sources. It also contains naturally occurring estrogen-like substances called isoflavones. These plant molecules are being evaluated clinically as chemo-preventive agents on prostate cancer. Talk to your doctor before you consider taking soy isoflavones in supplement form.
Soy Composition
Soy provides essential nutrients such as protein, essential fatty acids and vitamins and minerals, including vitamins A and C, calcium and iron, which are critical to the proper functioning of your body. A pale yellow oil is extracted from soy that is high in heart-healthy polyunsaturated fats, specifically linoleic and linolenic acids.
Prostate Cancer
Prostate cancer arises when a malignant tumor forms in the prostate, a part of the male reproductive system that produces fluid for sperm. In the United States, prostate cancer is the most commonly diagnosed cancer in men after lung cancer. It mainly affects men age 50 and older. Initially, prostate cancer has few or no symptoms, but an advanced cancer may cause difficulty in urination, painful ejaculation and pain in the back and rectum.
Soy Protein and Prostate Cancer
In cell culture and animal studies, the isoflavones found in soy reduced the serum levels of testosterone, a male reproductive hormone that allows prostate tumors to grow. Soy isoflavones increase the level of a sex-hormone-binding globulin, or SHBG, that binds to testosterone and decreases the relative amount of free testosterone in the blood.
Soy Foods Vs. Soy Supplements
Phytochemicals isolated from soy, such as isoflavones, have been found to inhibit platelet aggregation or blood clotting and thus reduce the risk of heat attacks and strokes. However, taking isolated nutrients through supplements is not as effective as consuming them in soy foods. The best way to improve your health is through natural soy foods like tofu, soy milk, soy sprouts, soy flour, tempeh and miso, according to a 2011 study at University of Georgia.
Side Effects
Limit your intake of soy when you have a known food allergy. With soy allergies, the body's immune system mistakenly attacks the allergens found in soy protein. In an attempt to protect the body, the immune system produces chemicals to combat these substances. People allergic to soy may suffer from as skin reactions, itching, breathing difficulty, wheezing, vomiting, diarrhea and a drop in blood pressure. Soy isoflavones also impair thyroid function by interfering with iodine uptake, so people with hypothyroidism should avoid soy foods.
References
- University of Maryland Medical Center: Soy
- Ohio State University: Department of Food Science & Technology: Soybeans Protein
- University of Maryland Medical Center: Prostate Cancer
- Cedars-Sinai Medical Center: Soy for Prostate Cancer
- "American Society for Nutritional Sciences"; Gaining Insight into the Health Effects of Soy but a Long Way Still to Go; Mark Messina and et al.; 2002
- "Food Allergies: Let Us Know, We Care"; Alfonso Tirado; 2005
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