Walnuts may slow prostate cancer

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SAN FRANCISCO — Prostate tumors grew more slowly in mice fed a diet rich in walnuts, Paul Davis of the University of California, Davis reported March 22.

Previous work has shown that walnuts can benefit the heart by fighting inflammation and allowing blood vessels to dilate. Davis notes that inflammation also plays a role in many cancers, and that walnuts can tinker with production of endothelin, a protein that helps regulate prostate growth.

To study how walnuts affect prostate cancer, Davis and his colleagues studied mice genetically programmed to develop the disease. When the animals are fed a normal quantity of fat for mice — 5 percent of calories — the tumors grow slowly. But bump dietary fat up to a whopping 20 percent of calories and tumor growth mushrooms, Davis reported — except if that 20 percent of fat calories comes from walnuts. Cancer in those mice grew slowly, similar to the rate seen in animals downing a low-fat diet. A man would have to consume about 500 calories’ worth of walnuts to equal what the mice ate, Davis says.

Janet Raloff is the Editor, Digital of Science News Explores, a daily online magazine for middle school students. She started at Science News in 1977 as the environment and policy writer, specializing in toxicology. To her never-ending surprise, her daughter became a toxicologist.

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