Study Suggests Western Diet tied to Prostate Cancer

NEW YORK (Reuters Health) - Prostate cancer is 10 times more common in the United States than Japan and preliminary research suggests that differences in diet may be a reason why.

There has been much speculation that the Western diet is a factor because when Japanese men move to the U.S. and start eating plenty of high-fat burgers and pizza and less soy, their risk of prostate cancer increases.

"Within one generation, the prostate cancer incidence begins skyrocketing," said study author Dr. Leonard S. Marks, a clinical associate professor of urology at the University of California at Los Angeles.

In a new study released Monday at a meeting of the American Urological Association in Chicago, Marks and colleagues examined blood and prostate cancer tissue samples and compared health data from 50 men who had undergone surgery to remove a cancerous prostate gland.

Half of the men lived in Japan, while the other half were Los Angeles residents born in the U.S. to Japanese parents. As such, both groups had similar genetic roots.

But there were marked differences in what they ate.

The Japanese-American men reported eating a diet substantially higher in animal fat. Not surprisingly, they also had a greater percentage of body fat and higher triglyceride levels in their blood.

The native Japanese men ate more soy than the Japanese-American men. Soy has been thought to possibly offer protection against prostate cancer.

"Soy didn't protect these men," Marks said, "but soy may be protecting many other men who don't get prostate cancer in Japan."

While the prostate cancer samples from the two groups appeared similar, detailed analysis of the tumor cells' genetic material told another story. "Since the DNA was arranged differently, there may be a gene-nutrient interaction responsible for the differences," Marks said.

"The cancers look the same but their genesis appears to be different, and that may be a result of diet," he told Reuters Health.

Still, much more research is needed to explain why prostate cancer rates vary widely around the world. "Does this study prove why the differences are there? It doesn't," Marks said. "It's a first step."