Isoflavones Seen Protective Against Development of Localized Prostate Cancer

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NEW YORK (Reuters Health) Mar 29 - Dietary isoflavones may reduce the risk of developing localized prostate cancer, but appear to be associated with advanced disease when prostate cancer does occur, according to a report from Japan in the March issue of Cancer Epidemiology, Biomarkers & Prevention.

"Isoflavone intake from traditional Japanese food throughout life may be protective for incidence of prostate cancer," Dr. Norie Kurahashi told Reuters Health, "but we can not recommend intake of isoflavones from supplements to persons who do not consume isoflavones regularly, because isoflavones may increase the risk of advanced prostate cancer."

Dr. Kurahashi and associates from the National Cancer Center, Tokyo, investigated the association between isoflavone intake and risk of prostate cancer in a prospective study of Japanese men, who generally consume large amounts of soy products and have a low incidence of prostate cancer.

The study involved some 43,500 men followed from 1995 through 2004. During that time, 307 of them were newly diagnosed with prostate cancer.

Consumption of isoflavones (principally genistein, but also daidzein and soy foods) was associated with a decreased risk of localized prostate cancer, the authors report. Genistein and daidzein, however, were associated with an increased the risk of advanced prostate cancer, the results indicate.

The protective effect of isoflavones for localized prostate cancer was clearest among men over 60 years old, the researchers note, as was the association of isoflavone consumption with an increased risk of advanced prostate cancer.

"We suggest that isoflavones delay the progression from latent cancer to clinically significant prostate cancer in Japanese who consume isoflavones regularly throughout life," Dr. Kurahashi said. "However, we do not know when or how isoflavones affect latent or localized prostate cancer development and whether isoflavones can be used in the treatment or chemoprevention of this cancer."

"We think further studies to clarify what period in life soy consumption exerts an effect against prostate cancer and what type of prostate cancer it can prevent are needed," Dr. Kurahashi concluded.

Cancer Epidemiol Biomarkers Prev 2007;16:538-545.

Source: http://www.medscape.com/viewarticle/554300?src=mp