Men, if you want to help prevent prostate cancer, look to the Japanese — they seem to know something we don’t. A recent study has shown that isoflavones, substances contained in soybeans and soy products, could be helpful in decreasing your risk for this type of cancer.
Isoflavones are plant-based compounds that can act as phytoestrogens and antioxidants. This stuff is chiefly found in legumes, such as fava beans, kudzu, chickpeas, peanuts, and soybeans. The two primary types of isoflavones found in soy are “genistein” and “daidzein.” The effects of these compounds are controversial — many claim that the stuff could protect against different types of cancer, while others say that phytoestrogens could actually encourage the growth of cancer.
In our Western society, rates of prostate cancer are quite high compared to those in Japan. According to the National Cancer Institute, prostate cancer ranks as the second most common cancer among men in the U.S. It’s estimated that there will be 218,890 new cases of the disease in the U.S. every year. The 2007 mortality rate due to this type of cancer is pegged at 27,050. So, finding ways to deal with prostate cancer is serious business. One of the best methods of doing this is to study people in countries where the incidences of the disease are lower. . . that’s where Japan comes into the picture.
To see what the deal was with soy and prostate cancer and to clarify the findings of previous smaller studies, Japanese researchers looked at the findings from a huge population study on 43,509 men in Japan. Aged 45 years to 74 years, the study participants were representative of Japanese men, in that they had high levels of isoflavone consumption and lower risk for prostate cancer. In 1990, the men were given questionnaires to fill out on their food habits, lifestyle, and medical history. Five years later, the participants filled out a follow-up survey. At the follow up, there were 307 new cases of prostate cancer among the men involved in the survey study.
Upon analyzing the survey data, the researchers found that, overall, the consumption of genistein, daidzein, miso soup or soy foods was related to a very small decrease in prostate cancer; in fact, the numbers here were not significant enough to really say there’s any real benefit. However, when they broke the data into stages — localized cancer (cancer that hasn’t yet spread) versus advanced-stage cancer — the information was more positive. The Japanese team found that the isoflavones significantly decreased the risk of localized prostate cancer, with genistein showing the best results. Men over 60 received the most benefit from having isoflavones in their diet. The higher their individual intake was, the lower their risk for localized cancer.
But, wait, there’s also bad news: the researchers discovered that greater intake of genistein, daidzein and miso soup upped the risk of advanced prostate cancer. Soy foods were mostly in the clear in this respect. Miso soup, with its very high isoflavone levels, seemed to be the worst offender.
These findings mean that isoflavones and soy products could be helpful in preventing prostate cancer, depending on what stage you’re at or the aggressiveness of the cancer, and depending on your age. According to the researchers, isoflavones might not be effective in men under 60 years old. Further research is required to figure out exactly when soy intake could be protective, versus risky. For now, if you’re a male older than 45, you need to discuss prostate cancer risks with your doctor. See what he or she has to say on that subject of adding soy to your diet.