Soy Isoflavones / Phytoestrogens Review & Information
Soy isoflavones are substances that occur naturally in soybeans. They are known as phytoestrogens, another name for compounds in plants that have estrogen-like properties. As a dietary supplement, soy isoflavones are popular among menopausal and perimenopausal women because they may help to ease symptoms like hot flashes and mood swings that are common in this stage of life.
In fact, it is possible that the prevalence of menopausal symptoms in the west is due to the fact that soy foods are not typically included in western diets. In contrast, menopausal symptoms are rare in Asian countries, where soy products are a dietary staple.
There are a number of soy isoflavones.
The compound known as genistein is the one that is most often sold in supplement form. Other active isoflavones in soy include daidzein, daidzin, glycitin and glycetein. One does not necessarily need to take supplements to obtain the benefits of soy and soy isoflavones. Another way is to eat soy-based foods such as tofu, tempeh, miso, soy milk and of course, soy beans.
A diet rich in soy is thought to help lower the risk of heart disease and cancer, particularly breast, prostate and endometrial cancers. In fact, in one study, the risk of endometrial cancer was 54% lower in women who regularly consumed soy products. The American Heart Association now recommends that Americans include 25 grams of soy protein per day to achieve health benefits for the cardiovascular system.
The ability of soy to protect against disease is due mainly to the actions of isoflavones, which can be thought of as the active ingredients in soy protein. Isoflavones protect the body in several ways. For one thing, they help to inhibit the growth of cells that cause plaque to build up in arteries. A diet rich in soy foods is therefore associated with lower levels of cholesterol in the blood.
Soy is also thought to inhibit the growth of cancer cells as well as cells of the prostate gland that can cause benign prostate enlargement in men. The isoflavones in soy protect bones and help keep them strong. There is some evidence that isoflavones can help to build new bone as well. A number of nutritional formulas for bone strength contain soy isoflavones in addition to calcium and vitamin D.
Soy isoflavones are natural plant hormones. While isoflavones are found in many other plant foods, soy is thought to be the most concentrated and easily available source. These compounds are rich in antioxidants, which further enhances their effectiveness in protecting against cancer and other diseases. Antioxidants prevent damage to cell DNA that occurs over time from the natural process of oxidation.
An effective daily dose of soy isoflavones is 500-1000 mg of soy extract that contains 13% to 17% genistein. A soy supplement should contain at least 10% total isoflavones. These supplements should be used with caution by pregnant women or by anyone who is allergic to soy protein. In rare cases, soy can interfere with thyroid function, though this would only be the case in the rare instance that iodine intake is inadequate.