Walnuts: good for the heart, prostate

Walnut consumption slows the growth of prostate cancer in mice and has beneficial effects on multiple genes related to the control of tumour growth and metabolism, researchers have found.

Paul Davis, nutritionist and researcher with the UC Davis Cancer Centre in California, said the findings provide additional evidence that walnuts, although high in fat, are healthy.

"This study shows that when mice with prostate tumours consume an amount of walnuts that could easily be eaten by a man, tumour growth is controlled," he said. "This leaves me very hopeful that it could be beneficial in patients."

Prostate cancer affects one in six American men. It is one in which environmental factors, especially diet, play an important role. Numerous clinical studies have demonstrated that eating walnuts -- rich in omega-3 polyunsaturated fats, antioxidants and other plant chemicals -- decreases the risk of cardiovascular disease.

Davis fed a diet with whole walnuts to mice that had been genetically programmed to get prostate cancer. After 18 weeks, they found that consuming the human equivalent of 2.4 ounces of walnuts per day resulted in significantly smaller, slower-growing prostate tumours compared to mice consuming the same diet with an equal amount of fat, but not from walnuts.

They also found that not only was prostate cancer growth reduced by 30 to 40 percent, but that the mice had lower blood levels of a particular protein which has been strongly associated with prostate cancer.

Additionally, Davis and his research colleagues looked at the effect of walnuts on gene activity in the prostate tumours using whole mouse gene chip technology, and found beneficial effects on multiple genes related to controlling tumour growth and metabolism.

"This is another exciting study from UC Davis nutrition researchers, where truly promising results that have a molecular footprint are having beneficial effects against cancer," said Ralph deVere White, UC Davis Cancer Centre director and a prostate cancer researcher. "We have to find a way to get these kinds of studies on nutritional products funded so that we can truly evaluate their effects on cancer patients.

"The bottom line is that what is good for the heart -- walnuts -- may be good for the prostate as well," he said.

The findings were presented Monday at the annual national meeting of the American Chemical Society in San Francisco.