Omega-3 fatty acids reduce prostate cancer growth

The August 1, 2006 issue of the journal Clinical Cancer Research published the finding of researchers at UCLA that a greater ratio of omega-3 to omega-6 fatty acids in the diet was associated with a reduction in prostate tumor growth rates and prostate-specific antigen (PSA) levels in a mouse model of hormone-sensitive prostate cancer. Omega-3 fatty acids consist of EPA and DHA, found in oily fish and the algae that they feed on, and ALA, found in flax and other plants. Omega-6 fatty acids are found mainly in vegetable oils such as those derived from corn and safflower, and are also found in red meat.

David Geffen School of Medicine department of urology professor William Aronson and colleagues used immunodeficient mice injected with human prostate cancer cells for the current study. One group of mice was provided with a diet that contained 20 percent fat consisting of a 1 to 1 ratio of omega-3 to omega-6 fatty acids, while a second group received the same diet with its 20 percent fat content consisting mostly of omega-6 fatty acids. The animals' weights and tumor volumes were measured weekly. After eight weeks the animals' tumors were examined and blood serum was analyzed for PSA.

The research team found a 22 percent average reduction in tumor cell growth rates and 77 percent lower PSA levels among mice who received the omega-3 fatty acids compared to animals whose dietary fats were predominantly omega-6. Pro-inflammatory prostaglandin (PGE-2) levels were 83 percent lower in the tumors of mice who received the high omega-3 diet than in mice on the omega-6 fatty acid diet.

An increased omega-3 to omega-6 fatty acid ratio results in higher tumor EPA and DHA content and a reduction in arachidonic acid. These fatty acids compete to be converted by cyclooxgenase enzymes (COX) into prostaglandins, which can become either pro-inflammatory or anti-inflammatory and reduce growth. Higher levels of DHA and EPA may lead to development of more anti-inflammatory prostaglandins.

The study is among the first to demonstrate the effect of reducing a prostate cancer- promoting inflammatory response via diet. Dr Aronson commented, "Corn oil is the backbone of the American diet. We consume up to 20 times more omega-6 fatty acids in our diet compared to omega-3 acids. This study strongly suggests that eating a healthier ratio of these two types of fatty acids may make a difference in reducing prostate cancer growth, but studies need to be conducted in humans before any clinical recommendations can be made."

"We may be able to use EPA and DHA supplements while also reducing omega-6 fatty acids in the diet as a cancer prevention tool or possibly to reduce progression in men with prostate cancer," Dr Aronson added. The team is currently conducting a trial which will compare the effects of a low-fat diet supplemented with omega-3 fatty acids to those of a balanced Western diet on men whose prostate glands were removed due to prostate cancer.