Even men genetically predisposed to disease benefit from eating fish, study finds
TUESDAY, March 24 (HealthDay News) -- Omega-3 fatty acids could help protect men against advanced prostate cancer, researchers report.
Eating fish at least once a week may reduce the risk of developing advanced prostate cancer even if one is genetically predisposed to developing the disease, but more work is needed to see if the association is real, the researchers said.
"Eating a healthy diet that includes dark fish and other sources of long-chain omega-3 fatty acids may decrease risk of more advanced prostate cancer even if one has a cox-2 genetic predisposition to the disease," said lead researcher John S. Witte, a professor in the Institute for Human Genetics, Epidemiology & Biostatistics at the University of California, San Francisco.
The report is published in the April issue of Clinical Cancer Research.
For the study, Witte's team studied 466 men with aggressive prostate cancer and 478 healthy men. The researchers collected data on the men's diet and genetically assessed nine cox-2 single nucleotide polymorphisms.
"We detected strong protective associations between increasing intake of long-chain omega-3 polyunsaturated fatty acids and more advanced prostate cancer," Witte said. "These fatty acids are primarily from dark fish such as salmon."
This association held even if men had a high-risk genetic variant in the cox-2 gene, Witte said. "In contrast, men with low intake of dark fish and the high-risk variant had a substantially increased risk of more advanced prostate cancer," he noted.
The researchers found that men who had the highest intake of omega-3 fatty acids had a 63 percent lower risk of aggressive prostate cancer compared with men with the lowest intake of omega-3 fatty acids.
Then the researchers looked at the effect of omega-3 fatty acid in men with a cox-2 variant called rs4647310, a known inflammatory gene. Among men with low omega-3 fatty acid intake and this variant, the risk of developing advanced prostate cancer increased fivefold. However, men who had a high intake of omega-3 fatty acids had a significantly lower risk, even if they had the cox-2 variant.
These findings suggest that eating fish or other sources of long-chain omega-3 polyunsaturated fatty acids may decrease a man's risk of being diagnosed with more advanced prostate cancer, Witte said. "And the decrease in risk may be even more pronounced if one has a high-risk genetic variant in the cox-2 gene."
Focusing on more advanced tumors is important, since these tumors are most likely to take an aggressive course and thus impact a man's survival, he added. "Moreover, our results further support the hypothesis that long-chain omega-3 polyunsaturated fatty acids may modify prostate inflammation through the cyclooxygenase (cox) pathway," Witte said.
Eric Jacobs, strategic director of pharmacoepidemiology at the American Cancer Society, thinks the jury is still out on connecting omega-3 fatty acids with a reduced risk of advanced prostate cancer.
"In this study, a diet high in long-chain omega-3 fatty acids was associated with lower risk of developing advanced prostate cancer," Jacobs said. "However, some previous studies did not find similar results."
Indeed, other research has proved fruitless when it comes to using supplements to help prevent prostate cancer. Two studies released in January in the Journal of the American Medical Association found no evidence of benefit from supplemental selenium, vitamin E or vitamin C on prostate cancer and other cancers. Other recent studies have suggested that vitamins, B, C, D, E, folic acid and calcium taken alone, or in various combinations, aren't effective for cancer prevention either.
Nevertheless, more research into omega-3s role in prostate cancer prevention is needed, Jacobs said.
"One way men can reduce their risk of developing advanced prostate cancer, as well as risk of many other diseases, is to maintain a healthy weight. Many studies have shown that being obese is associated with increased risk of developing advanced prostate cancer," he said.
For more about prostate cancer, visit the American Cancer Society.
SOURCES: John S. Witte, Ph.D., professor, Institute for Human Genetics, Epidemiology & Biostatistics, University of California, San Francisco; Eric Jacobs, Ph.D., strategic director, pharmacoepidemiology, American Cancer Society, Atlanta; April 2009, Clinical Cancer Research
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