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 study is not the first to find that men who eat fatty fish have a lower risk for the most deadly forms of prostate cancer. But Witte says clinical trials are needed to show that eating foods high in omega-3 fatty acids actually lower risk of aggressive prostate cancer.
The study appears in the April issue of Clinical Cancer Research.
"There is a lot of evidence that omega-3 fatty acids protect against heart disease and other diseases by targeting inflammation -- and that may be what is going on here," Witte says.
Omega-3 and Prostate Cancer
The study by Witte and colleagues from the University of California, San Francisco, included 466 men with aggressive prostate cancer and 478 men without the cancer.
The men were asked to fill out food-frequency questionnaires. Genetic analysis was also performed to identify variants of the Cox-2 gene, which helps regulate inflammation within the body. A certain variant of this gene is also known to increase the chance of developing prostate cancer.
The analysis revealed that men who ate little to no fatty fish and had a specific Cox-2 variant were five times more likely to develop advanced prostate cancer.
But men with the highest intake of omega-3 fatty acids -- equivalent to one or more servings of fatty fish a week -- had a significantly reduced risk for advanced disease, even when they carried the Cox-2 variant.
"The increase in risk associated with having the Cox-2 variant was essentially reversed in men who ate fish one or more times a week," Witte says.
Clinical Trials Needed
Omega-3 researcher Jorge Chavarro, PhD, of Harvard Medical School tells WebMD that the findings are consistent with his own studies of omega-3 and prostate cancer.
In a 2007 study, Chavarro and colleagues with the Harvard School of Public Health reported a 41% reduction in prostate cancer risk among men who ate higher levels of omega-3s than men with the lowest intake.
In separate studies, the Harvard team found that men who ate fatty fish before being diagnosed with prostate cancer and after their diagnosis were less likely to die of the disease.
Chavarro's research also suggests that omega-3 is particularly protective against the most aggressive prostate cancers.
He tells WebMD that this supports the growing belief that prostate cancer is a more complex disease than previously thought.
"We call everything prostate cancer, but clinically aggressive cancers and more localized, benign cancers may be two very different diseases," he says. "In the past we have studied overall disease. But it may be that the effects of fish and other anti-inflammatory interventions, like Cox-2-targeting drugs, affect only aggressive disease."
Roswell Park Cancer Institute President and professor of oncology Donald Trump, MD, tells WebMD that there is enough evidence suggesting a protective role for omega-3 against prostate cancer to justify a large trial studying whether eating a diet rich in omega-3s -- or even taking omega-3 supplements -- can actually lower risk of prostate cancer.
"This is a very nicely done study, but we definitely need a clinical trial," he says. "These results suggest that we may be able to identify men who will be most likely to benefit and least likely to benefit from this intervention."
Fish rich in omega-3 fatty acids include: