Japanese men have lower rates of prostate cancer than men in the United States, and some experts contribute that to the Japanese diet, which is high in soy foods. The results of a few animal studies showed promise in this area. However, two small studies on humans (men) yielded controversial results. Soy isoflavones appeared to lower and improve the PSA (prostate-specific antigen) score for some men. For others, PSA level increased, but at a slower rate. And for certain men, the isoflavones worsened the prostate cancer condition. The bottom line: There are not enough human studies to say whether the isoflavones in soy affect prostate cancer for better or for worse.
Does soy relieve hot flashes, night sweats and other menopausal symptoms? Could soy isoflavones be the reason that Japanese women have a lower rate of hot flashes? Current research does not indicate this and study results have been very inconsistent. Roughly 60 percent of trials showed only modest reductions in hot flashes, while the other 40 percent showed no improvements. The bottom line: The claims that soy helps with menopausal symptoms have been blown way out of proportion. The evidence just does not show much benefit.
It is still too early to conclude whether or not soy helps to build bones. There are currently a few long-term studies investigating the area of soy and bone health. Contrary to popular belief, Japanese women experience as much (if not more) osteoporosis as Caucasian women in the United States. They do suffer fewer bone fractures, but this may be due to genetics or the shape of their bones. The bottom line: Although it will be a few years before the long-term studies conclude, it does look like soy may benefit the bones. Although soy probably does NOT reverse bone loss, it may help prevent bone loss and increase bone density.
Does soy improve ones cognitive functioning? Very little research has been conducted in this area. But one small, preliminary study on older adults showed that soy isoflavones did improve cognitive functioning. The bottom line: More investigation is needed in this area. Continued ›