Benefits of soyThere is no denying that soy has many health benefits, which are coming form the quality of the soy proteins and from health promoting phytochemicals, such as isoflavones, phytates, saponins and polyphenols. Epidemiological studies suggest that soy consumption is associated with lower incidences of chronic diseases. Lower rates of hearth disease and some types of cancers have been attributed to the consumption of large quantities of soy foods in Asian countries[1-2]. Consumption of isoflavones, the main phytochemical in soy, may have beneficial effects on heart disease, bone health, prevention of obesity and some types of cancer.
Bone healthAlthough soy products, such as soy milk and tempeh, are not a rich source of calcium, they can help reduce the risk of osteoporosis. Several studies have suggested that soy isoflavones may be a factor in helping to prevent bone loss. The soy isoflavone genistein seems to inhibit bone breakdown and may have similar effects than estrogens in maintaining bone tissue. A recent meta-study carried out by Pan Wei showed that soy isoflavones supplements significantly increase bone mineral density in women .
Menopausal symptomsEpidemiological data show that Asian women suffer less from hot flashes and night sweats than Western women. Most symptoms of menopause are caused by low estrogen levels. Estrogens play a role in the body temperature control. Soy isoflavones can through their estrogen-like effect control these menopausal symptoms, especially hot flushes.
Heart healthIn countries with high soy intake the rates of cardiovascular diseases is relatively low. Research suggests that soy may help to prevent heart disease by reducing total cholesterol, low density lipoprotein cholesterol and preventing plaque buildup in the arteries, which could lead to stroke or heart attack. These health benefits are also mainly attributes to the soy isoflavones and saponins. The soy isoflavone genistein may increase the flexibility of blood vessels, whereas saponins may have potential to reduce blood cholesterol.
Cancer preventionSeveral studies have indicated that a regular intake of soy foods may help to prevent hormone related cancers such as breast cancer, prostate cancer and colon cancer. A Chinese study found that high dietary intake of soy isoflavones was associated with lower risk of recurrence among postmenopausal women with estrogen and progesterone positive breast cancer and those receiving the anti-cancer drug anastrozole. The scientists suggest that the beneficial effects of soy isoflavones is exerted through their interaction with estrogen and progesterone receptors. Isoflavones have antiangiogenic activity, which means that they interfere with blood vessel growth, an important anticancer property.
High protein contentSoy products such as tofu, tempeh and soy milk are very rich in protein, which is of very high biological quality as it contains all essential amino acids. In addition, the amino acids of soy combine very well with those of cereals, such as wheat, rice and corn. Soy protein is especially important for vegans.
References Soy intake and risk of breast cancer in Asians and Asian Americans. Am J Clin Nutr. 1998 Dec;68
 Modern applications for an ancient bean: soybeans and the prevention and treatment of chronic disease. J Nutr. 1995 Mar;125
 Systematic review of soy isoflavone supplements on osteoporosis in women. Asian Pacific Journal of Tropical Medicine. 2012 Mar;5(3):243-8.