Correlation is not causation. But people who eat foods high in omega 3 fatty acids appear to get less aggressive prostate cancer.

March 24, 2009 -- Men who eat salmon and other fish high in omega-3 fatty acids on a regular basis have a decreased risk for developing advanced prostate cancer, new research suggests.

The association was most pronounced among men believed to have a genetic predisposition for developing aggressive prostate cancer.

Men in the study who ate one or more servings of fatty fish a week were found to have a 63% lower risk for developing aggressive prostate cancer than men who reported never eating fish, study co-researcher John S. Witte, PhD, tells WebMD.

The benefit might flow from blocking inflammation caused by a COX-2 gene variant.

A similar trend was seen for different levels of shellfish intake. Shellfish also contains omega-3 fatty acids. Omega-3 intake also had a major impact on the effect of a hazardous variant of the COX-2 gene, which promotes inflammation and is known to be linked to prostate cancer.

Men with the variant have a more than five-fold increased risk of aggressive prostate cancer. But a high consumption of oily fish effectively wiped out this risk factor.

A half gram of omega 3 looks like enough to do the trick for people who have a high risk genetic variant of COX-2. So maybe the 3 fish oil capsules I take per day might be sufficient.

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.

"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 Witte. "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."

Here is a more technical discussion of the results.

For an additional potential prostate cancer risk reduction eat fish with mushrooms.