Health and dietary professionals revere soybeans and soy products, such as soy milk and tofu, for their superior nutritional value. Most of the research surrounding soybeans today pertains to both their potential beneficial and adverse effects on health. Researchers primarily attribute these effects -- both positive and negative -- to the presence of isoflavones, hormones that are highly concentrated in soybeans.
Isoflavones and Estrogen
Isoflavones have chemical structures similar to the hormone estrogen. Estrogen is present in both men and women, but is higher in women, especially during their reproductive years. Estrogen participates in a variety of functions in the body. In its primary role, it regulates the development of secondary sex characteristics, the menstrual cycle and uterine growth.
Menopause
As you approach menopause, your ovaries decrease and eventually halt their production of estrogen. This absence causes many of the side effects associated with menopause, including hot flashes and night sweats. Several clinical studies report that postmenopausal women who consumed high amounts of soy products experienced fewer side effects. Researchers attribute this to the estrogen-mimicking action of isoflavones, which help relieve withdrawal symptoms. However, the University of Maryland Medical Center notes that other studies showed conflicting results.
Cancer
The effect of soybeans on cancer -- particularly breast cancer -- remains a highly controversial subject. Some studies show that soy isoflavones help prevent hormone-related cancers -- including prostate, breast and uterine tumors -- while others show no connection. According to the Harvard University School of Public Health, estrogen stimulates the growth of some types of breast tumors, which has led to the belief that the overconsumption of soy can trigger breast cancer. However, isoflavones do not always imitate estrogen; they can also block the action of estrogen in certain cells. These conflicting functions contribute to the confusion regarding the effect of soy isoflavones on breast and other cancers.
Osteoporosis
Another important role of estrogen includes its actions in maintaining bone density by reducing bone deterioration and promoting bone formation. This regulation declines during menopause as estrogen levels decrease, putting women at a higher risk for osteoporosis. The University of Maryland Medical Center notes that while studies are limited, available results show that women who consumed high amounts of soy products were most likely to maintain their bone density and prevent osteoporosis. Again, these effects are attributed to isoflavones mimicking estrogen.
References
- Linus Pauling Institute; Soy Isoflavones; J. Higdon; December 2009
- "Human Physiology: An Integrated Approach"; Dee Unglaub Silverthorn; 2006
- University of Maryland Medical Center; Soy; December 2009
- Harvard University School of Public Health: Protein: Moving Closer to Center Stage
