Men consuming high levels of soy products rich in isoflavones might be able to drastically reduce risk of prostate cancer, according to a Japanese study appearing in the August 2007 issue of Journal of Nutrition, a publication of American Society for Nutrition.

Yoshie Nagata and colleagues from Sapporo Medical University School of Medicine in Japan found that the risk of prostate cancer was reduced by more than 50 percent in the men studied.

Prostate cancer is the most common cancer in men and the second leading cause of cancer deaths in the United States.  According to the American Cancer Society, 218,890 new cases of prostate cancer will be diagnosed in the country this year and at least 27,050 will die from the disease. Worldwide, prostate cancer kills 200,000 people each year whereas some half a million are diagnosed with the disease each year.

The current study is an extension of an earlier one, which reported in Cancer Epidemiology Biomarkers & Prevention, Vol. 16, pp. 538-545 that high intake of isoflavones reduced the risk of prostate cancer in Japanese men.  

In the cases-control study, the researchers examined correlations between nutritional and other lifestyle factors and the prevalence of prostate cancer.

For the study, they analyzed intake of 12 food items in 200 Japanese men with various stages of prostate cancer as well as in 200 control cases.

The food items surveyed in the study included Tofu (soybean curd), natto (fermented soybeans), miso soup (soybean paste soup), bean curd refuse, fried bean curd, fried bean curd with vegetables, soy flour, dried bean curd, soybean milk, soy sauce, green soybeans, and bean sprouts.

The researchers said that people who took highest amounts of isoflavones called genistein and daidzein had a 58 percent decreased risk of prostate cancer as compared to those who consumed lowest amounts.

However, they cautioned that the study could not be generalized because Japanese diet differs from traditional Western diets. "Serum phytoestrogen concentrations are higher among Japanese men and women than among those in Western countries," the authors stressed.

Soy isoflavones, similar in chemical structure to estrogens, inhibit 5 alpha-reductase, an enzyme involved in the metabolism of testosterone and reduce the level of the male hormone.   High levels of the hormone are a risk factor for prostate cancer.

Soy or soy foods are the main sources of isoflavones, phytochemicals that are also known as natural antioxidants. Previous studies have linked them with reduced symptoms associated with menopause, heart disease and osteoporosis.

Source:

Nagata Y, Sonoda T, Mori M, Miyanaga N, Okumura K, Goto K, Naito S, Fujimoto K, Hirao Y, Takahashi A, Tsukamoto T, Akaza H.   Dietary Isoflavones May Protect against Prostate Cancer in Japanese Men J Nutr. 2007 Aug;137(8):1974-1979.

###

.

Copyright 2007 foodconsumer.org .   All rights reserved.   Foodconsumer.org publishes daily news and reports on food and diet, some of which are not available from the mainstream news media.  This article can be used by individuals and organizations for not-for-profit purposes without prior express permission from foodconsumer.org on condition that this article including the author and this copyright note should be used in entirety without alteration.