Study links diet and prostate cancer at the tissue level

A Western diet high in animal fat and low in soy creates malignant transformation in the prostate tissue, according to a study that may explain why Asian men have lower rates of prostate cancer than their Western counterparts.

Compared with Japan and other Asian countries, the prevalence of prostate cancer is 10-fold greater in the United States. When Asian men move to Western countries and adopt a Western lifestyle, the protection disappears within one generation.

"We chose to study prostate cancer in men with the same genetics (all of Japanese descent), but with differing diets--one Eastern and one Western--to see if dietary differences translate into differing tissue effects," said principal author Leonard S. Marks, MD, of UCLA and Urological Sciences Research Foundation.

The 5-year collaboration between U.S. and Japanese scientists analyzed diets and prostate tissue in 25 native Japanese men compared with 25 second-generation or third-generation Japanese-American men.

The body composition between the two groups was measurably different. The Japanese-American men were about 5 years older than the Japanese men and had a greater percentage of body fat (24% vs. 19%).

The serum triglyceride levels were also considerably higher in Japanese-American men (245 mg/dL vs. 106 mg/dL, p<0.01), while the soy metabolites daidzein and genistein was threefold to fourfold greater in the native Japanese group.

The authors said there appeared to be oxidative damage from the saturated fats in a Western diet, while there was a protective effect from soy phytoestrogens in a Japanese diet.

The study was published in Urology (2004; 64:765-71).