Walnuts, and oil made from them, have been shown to slow the growth of prostate cancer, and also reduce cholesterol levels and increase insulin sensitivity.
 

The findings, led by researchers at the University of California-Davis, are based on studies involving laboratory mice, but are also believed to have implications for people, as well.
 

The new research, published online in the Journal of Medicinal Food, found that the health benefits of diets rich in whole walnuts or walnut oil reduce levels of the hormone IGF-1, which had been previously implicated in both prostate and breast cancer. The researchers suggested the findings are the latest to challenge the long-held nutritional advice that low-fat foods are healthier.
 

“For years, the United States government has been on a crusade against fat, and I think it’s been to our detriment,” said lead 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.”
 

For the new study, mice were fed whole walnuts, walnut oil, or walnut-like fats containing omega-3 fatty acids for 18 weeks. The results showed that the walnuts and walnut oil reduced cholesterol and slowed prostate cancer growth. But the walnut-like fat did not have these effects, confirming that other nut components caused the improvements — not the omega-3s.
 

“We showed that it’s not the omega-3s by themselves, though, it could be a combination of the omega-3s with whatever else is in the walnut oil,” Davis said. “It’s becoming increasingly clear in nutrition that it’s never going to be just one thing; it’s always a combination.
 

“It’s the holiday season, and walnuts are part of any number of holiday dishes. Feel free to consume them in moderation.”
 

This study was funded, in part, by American Institute for Cancer Research and the California Walnut Board.