Walnuts may help fight prostate cancer

March 22nd 2010 - Scientists in California are reporting that walnuts reduce the size and growth rate of prostate cancer in test animals.

The findings were announced at the 239th National Meeting of the American Chemical Society (ACS), the world’s largest scientific society.

"Walnuts should be part of a prostate-healthy diet," said Paul Davis, PhD., the research nutritionist, who headed the study. "They should be part of a balanced diet that includes lots of fruits and vegetables."
Prostate cancer is the most common cancer in men in the UK. A quarter of all new cases of cancer diagnosed in men are prostate cancers.

The Prostate Cancer Charity is the UK’s leading charity working with people affected by the disease. It says one man dies every hour in the UK from prostate cancer.

Why walnuts?

Davis and his fellow researchers noted that walnuts were a rich source of healthful substances, including omega-3 fatty acids, gamma tocopherol (a form of vitamin E), polyphenols, and antioxidants.

The scientists recently showed that walnuts could help fight heart disease by reducing levels of endothelin, a substance that increases inflammation of blood vessels. Knowing that men with prostate cancer have elevated levels of endothelin, the scientists decided to test whether eating walnuts could be beneficial to them.

In a press statement Davis said, "We decided to use whole walnuts in the diet because when a single component of a food linked to cancer prevention has been tested as a supplement, that food's cancer-preventative effects disappear in most cases."

The science

The scientists from the University of California-Davis fed lab mice genetically programmed to develop prostate cancer the equivalent of 14 shelled nuts a day for two months.

A control group of mice got the same diet except with soybean oil. The walnut-fed mice developed prostate cancers that were about 50% smaller than the control mice. Those cancers also grew 30% slower.

The scientists also reported that the walnut-fed mice had lower levels of insulin-like growth factor-1. High levels of this protein may increase the risk of developing prostate cancer in the first place.

Risk factors

There are a number of risk factors for prostate cancer and age is the most significant. According to Cancer Research UK nearly six out of 10 cases (57%) are in men over 70. It is quite rare in men under 50.
You may also be more at risk if you have a family history of prostate or breast cancer or are black (of African ancestry) as prostate cancer is more common in black and mixed race men than white or Asian men.

Your diet may affect your risk. There is currently a lot of research underway into diet and Cancer Research UK says the evidence is not strong but you may increase your prostate cancer risk if you eat a diet high in dairy products. There is some evidence that lycopene from tomatoes may lower the risk.

Dr Helen Rippon, Head of Research Management at The Prostate Cancer Charity, explains, “The role of a healthy diet in the development and growth of prostate cancer has been a focus of research attention for many years. Yet, despite the level of research attention, there is very little practical advice available for men wishing to reduce their risk of the disease.”