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By Daniel Gastelu Section 7. Soy Bioflavonoids When searching the world for the perfect nutraceutical food-a food that not only provides nutrition, but also has health promoting and healing effects-we are (once again) led to Asia. The thousands of studies performed on soy have determined that its consumption can reduce cancer and heart disease, reduce bone loss, and help reduce the unpleasant symptoms of menopause. Most likely, all the components of soy have synergistic, or complementary, effects. Yet, many researchers have begun to focus on a special group of bioflavonoids contained in soy-the isoflavones, which are major players in soy's many health benefits. Q. Exactly what is soy? A. The products found in soy or soya foods and supplements are derived from the soybean of the Glycine max plant, which belongs to the pea family. Soybeans are native to China and their use and cultivation dates back several thousand years. Soybeans are now a major crop grown in the United States, and yield many useful products, such as soy protein, fiber, lecithin, and soy flour. Q. How do the isoflavones genistein and daidzein fit into the soybean picture? A. Genistein and daidzein are specific types of isoflavones. During the past two decades, researchers have linked these isoflavones, in part, with the health effects brought about by eating soybeans and soybean products. Along with characteristic antioxidant properties, these isoflavones are said to exhibit estrogen-like activity, which has a weak estrogenic effect under certain circumstances. This phytoestrogenic activity of the isoflavones is particularly important for soy's beneficial effects in menopausal women. Q. Exactly what effects do the isoflavones have on menopause? A. In the January 1998 issue of Journal of Obstetrics & Gynecology, Paola Albertazzi and coworkers reported the results of their twelve-week study on the effect of dietary soy supplementation on the frequency of hot flushes (also called hot flashes). The researchers examined the effects of eating 60g per day of isolated soy protein, compared to a placebo. The daily dosage of soy protein supplied 40mg of genistein and 28mg of daidzein. The female subjects ranged in age from forty-five to sixty-two years old. To qualify for the study, the women had to be experiencing a minimum of seven hot flushes per twenty-four-hour period, including night sweats. After two weeks, a major decrease in the number of hot flushes was noted in the soy group, and only a minor one in the placebo group. By the end of the study, the women taking soy experienced a major reduction in hot flushes and other menopausal symptoms. Q. What effects do soy bioflavonoids have on reducing the risk of cancer? A. Soy has two different avenues for preventing cancer. The first is the phytoestrogenic action of the isoflavones. The ingestion of foods with weak estrogenic activity by women usually results in a drop in estrogen blood levels-high estrogen blood levels is a risk factor for breast cancer. In animal studies, genistein-treated rats exhibited lower breast cancer rates. This experimental data supports the demographic relationship observed in populations consuming high amounts of soy. Genistein has also been shown to inhibit human breast cancer cell growth in tissue cultures. Other researchers have observed lower rates of endometrial cancer-a cancer that occurs in the wall of the uterus-in populations consuming a diet rich in soybeans and other legumes. Even men experience a reduced risk of cancer. Asian men who eat a low-fat, high-fiber, high-soy diet have been observed to have a lower rate of prostate cancer than North American and European men. Further studies have shown a reduced rate of cancer in laboratory tests and in populations due to soy's growth-inhibiting effects, which decrease tumor multiplicity. The second avenue is soy's antioxidant properties. Remember, antioxidants such as the bioflavonoids can neutralize a variety of reactive chemicals in the body. Their main function is to deactivate free radicals, resulting in fewer reactive chemicals that can potentially damage cellular DNA. Furthermore, the same way that antioxidants neutralize free radicals, isoflavones can lockup and deactivate carcinogenic compounds that enter the body. The net effect of increasing the amount of antioxidants in the body is reduced damage to cells and DNA, which in turn lowers the risk of degenerative diseases and cancers. Note that recent research indicates that people with a history of cancer need to work closely with their doctors to verify if they are following the proper diet and to determine if and how soy products should be used in their diets. Q. How do soy isoflavones reduce the risk of heart disease? A. A quick review of the results published in the New England Journal of Medicine will help answer this question. In 1995, Dr. James Anderson and coworkers looked at the combined results of twenty-nine studies that examined the effects that soy consumption had on reducing blood lipid-cholesterol and fatty acids-levels. (In scientific circles, this type of study is called a meta-analysis because it compares the results of many studies.) In Anderson's meta-analysis, he found that a significant reduction in total cholesterol, LDL-cholesterol, and triglycerides coincided with the average intake of soy protein of 47g per day. In a more recent study conducted at the Wake Forest University Baptist Medical Center, researchers reported that the cholesterol-lowering effect of soy protein is due to its isoflavone content. The researchers gave patients a soy drink containing soy protein with different amounts of isoflavones, or a drink that did not contain any isoflavones. In just nine weeks, there was a 10-percent reduction of total cholesterol and LDL-cholesterol in the isoflavone group. The researchers also noted that the higher the concentration of isoflavones, the greater the reduction in both LDL-cholesterol and total cholesterol. The isoflavone amounts that caused these beneficial results were 25 to 58mg per day. Q. What other beneficial health effects do the isoflavones have? A. In addition to lowering the "bad" cholesterol in the blood, isoflavones may also improve the elasticity of arteries. This may help cure and reduce the risk of arteriosclerosis, or hardening of the arteries. The phytoestrogen effect of isoflavones may also help reduce bone loss and osteoporosis. Genistein has been found to bind to estrogen receptors in bone in a similar way to that of estrogen. This may explain the beneficial effects it has on reducing bone loss. Estrogens have a well known effect on inhibiting bone-degrading cells. A study conducted in 1996 by Dr. John Erdman found that women taking soy supplements containing isoflavones experienced an increase in bone-mineral content and bone density. Dr. Erdman gave sixty post-menopausal women isoflavone-containing supplements of 55.6mg or 90mg, each day. A control group received a placebo-an inert substance. After six months, the women consuming the soy supplements showed improvements in bone density and mineral content when compared with the control group. Both isoflavone dosages worked equally as well. Q. How do You increase the amount of isoflavones in my diet? A. If you want to increase the amount of soy isoflavones in your diet, you should start eating more soybean products. These include soybeans, soy milk, soy protein drinks, soybean flour, soybean curd, tofu, soy-based cheese, soy nutrition bars, and miso. But, note that you must also be eating a healthy diet and living a healthy lifestyle. Just adding more soy containing foods and soy supplements to a diet that is low in nutrition and excessive in fats and calories will reduce the health benefits soy has to offer. Most scientific studies on soy isoflavones use soy protein drinks supplying 25 to 60g of soy protein and 68mg of isoflavones. Always choose soy based products that list the isoflavone content directly on the label. You may also want to consider taking a dietary supplement that supplies 20 to 60mg of isoflavones-depending on how much soy food you ingest each day.
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