Eating high amounts of soy seems to protect older men from prostate cancer, according to new findings from Japan.

Researchers studied 43,509 men aged 45-74 in Tokyo and other cities, recording details about their diets. After 10 years, 307 of the men developed prostate cancer. Those who had consumed the most soy products were significantly less prone to the disease, results showed. The negative association was especially strong in those over age 60. In this group, men whose soy intake was in the highest quartile had a 48% lower risk of localized prostate cancer compared with men in the lowest consumption quartile.

“This is the first prospective study to report an inverse association between isoflavone [a phytoestrogen contained in soy] and localized prostate cancer in Japanese men, whose intake of soy food is high,” the authors write in Cancer Epidemiology Biomarkers & Prevention (2007;16:538-545). Their results support retroactive studies showing that soy food helps protect against some types of cancer.

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In a U.S. study last year, men on soy-heavy diets were found less likely to be infertile than those who consumed no soy products.