March 24, 2009

Greater omega-3 fatty acid intake associated with decreased risk of advanced prostate cancer

In an article published online on March 24, 2009 in the American Association for Cancer Research journal Clinical Cancer Research, scientists from the University of California, San Francisco report a protective effect of long chain omega-3 polyunsaturated fatty acids against advanced prostate cancer risk.

Professor of epidemiology and biostatistics John S. Witte, PhD and his associates compared 466 men with aggressive prostate cancer to 478 healthy men matched for age and ethnicity. Dietary questionnaire responses were evaluated for omega-3 fatty acid intake, and blood samples were analyzed for nine variants in the gene that controls cylooxygenase-2 (COX-2), an enzyme involved in fatty acid metabolism, inflammation and cell proliferation. Earlier research has demonstrated decreased expression of COX-2 among animals fed high omega-3 fatty acid-containing diets, as compared to high omega-6 diets.

Advanced prostate cancer risk declined with increasing omega-3 fatty acid intake. Men whose intake of omega-3 fatty acids was among the top 25 percent of participants had a 63 percent lower risk of aggressive prostate cancer compared with those whose intake was in the lowest fourth. This association was stronger among men with a particular modification of the gene that controls COX-2 expression, resulting in an over five times greater risk of advanced prostate cancer in men with this variant who reported a low intake of omega-3 fatty acids. "Previous research has shown protection against prostate cancer, but this is one of the first studies to show protection against advanced prostate cancer and interaction with COX-2," Dr Witte stated. "The COX-2 increased risk of disease was essentially reversed by increasing omega-3 fatty acid intake by a half a gram per day."

"If you want to think of the overall inverse association in terms of fish, where omega-3 fatty acids are commonly derived, the strongest effect was seen from eating dark fish such as salmon one or more times per week," he added.

"Our study provides additional support for the role of inflammation in prostate cancer susceptibility and progression," the authors conclude. "More clinical and biological studies are needed to decipher how dietary long chain omega-3 and other factors involved with inflammation such as COX-2 genotypes affect aggressive prostate cancer