March 24, 2009 /PHILADELPHIA, AACR / – Omega-3 fatty acids appear protective against advanced prostate cancer, and this effect may be modified by a genetic variant in the COX-2 gene, according to a report in Clinical Cancer Research, a journal of the American Association for Cancer Research.

“The COX-2 increased risk of disease was essentially reversed by increasing omega-3 fatty acid intake by a half a gram per day,” said John S. Witte, Ph.D., professor of epidemiology and biostatistics at the University of California San Francisco.

If men want to interpret the results in terms of adding omega-3 rich fish to their regular diet, he said, “the strongest effect was seen from eating dark fish such as salmon one or more times per week.”

“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,” Witte said. Findings on benefits of salmon oil for protecting men with a Cox-2 gene variant from prostate cancer, pioneered in Sweden, were reported in 2007.

For the current US study, researchers performed a case-control analysis of 466 men diagnosed with aggressive prostate cancer and 478 healthy men. Diet was assessed by a food frequency questionnaire and researchers genotyped nine COX-2 single nucleotide polymorphisms.

Researchers divided omega-3 fatty acid intake into four groups based on quartiles of intake. Men who consumed the highest amount of long chain omega-3 fatty acids had a 63 percent reduced risk of aggressive prostate cancer compared to men with the lowest amount of long chain omega-3 fatty acids.

The researchers then assessed the effect of omega-3 fatty acid among men with the variant rs4647310 in COX-2, a known inflammatory gene.

Men with low long chain omega-3 fatty acid intake and this variant had a more than five-fold increased risk of advanced prostate cancer.

But men with high intake of omega-3 fatty acids had a substantially reduced risk, even if they carried the COX-2 variant.

SOURCES

American Association for Cancer Research.
Dietary Omega-3 Fatty Acids, Cyclooxygenase-2 Genetic Variation, and Aggressive Prostate Cancer Risk
Vincent Fradet, Iona Cheng, Graham Casey, and John S. Witte
Departments of Urology and Epidemiology and Biostatistics and Institute for Human Genetics, University of California at San Francisco, San Francisco, California and Department of Preventive Medicine, University of Southern California, Los Angeles, California

RELATED:

More Evidence that Fish Prevents Prostate Cancer - Canada, 2008
Salmon, Prostate Cancer and a COX-2 Variant — Sweden, 2007

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