An experiment on mice found that a diet rich in either whole walnuts or walnut oil slowed prostate cancer growth. "For years, the United States government has been on a crusade against fat, and I think it's been to our detriment," said University of California Davis scientist and research nutritionist Paul Davis. "Walnuts are a perfect example. While they are high in fat, their fat does not drive prostate cancer growth. In fact, walnuts do just the opposite when fed to mice."
Interestingly while walnuts (like fish) are high in omega-3's, it seems that there are other compounds in walnuts that fight prostate cancer, not just the omega-3s. The researchers point out that the mice were eating a lot of walnuts, but it might be worth the calories. "In our study the mice were eating the equivalent of 2.6 ounces of walnuts," he said. :"You need to realize that 2.6 ounces of walnuts is about 482 calories. That's not insignificant, but it's better than eating a serving of supersized fries, which has 610 calories. In addition to the cancer benefit, we think you also get cardiovascular benefits that other walnut research has demonstrated."