Increased intake of omega-3 fatty acids may cut the risk of colorectal cancer in men by a whopping 66 percent, but only in men not taking aspirin, reports new research. It has been proposed that omega-3 fatty acids may inhibit the omega-6 arachidonic acid (AA) inflammatory cascade that has been linked to cancer formation and cell proliferation.
Metabolism of fatty acids produces compounds called prostaglandins, which can be either pro- or anti-inflammatory. The prostaglandins derived from omega-3 fatty acids are said to be anti-inflammatory and may protect against the development of cancer, while prostaglandins derived from omega-6 fatty acids, like AA, are proposed to be pro-inflammatory.
Writing in the journal Cancer Epidemiology Biomarkers & Prevention, lead author Megan Hall from Harvard School of Public Health states that aspirin has also been linked to a reduction in colorectal cancer via a similar mechanism.
The new research investigated the link between the fatty acid concentrations in the blood of 178 men with colorectal cancer and 282 healthy controls free from cancer. The controls were matched by age and smoking habits. Dietary assessment was obtained by using food frequency questionnaires.
After adjusting the results for potential confounding factors, Hall and her co-workers from Harvard Medical School and Brigham and Women's Hospital, report that among the entire population the highest versus lowest blood levels for total long-chain omega-3 fatty acids were associated with a 40 percent reduced colorectal cancer risk. However, this was not statistically significant, said the researchers.
When they examined a subset of men who were not taking aspirin, men with the highest blood levels of omega-3 fatty acids were associated with a significant 66 percent reduced risk of colorectal cancer than those with the lowest blood levels.
Interestingly, higher blood levels of omega-6 fatty acids were also associated with a reduction in colorectal cancer risk (36 percent risk reduction), although this was not statistically significant.
The study adds to a growing body of science linking omega-3 and fatty fish consumption to a reduced risk of colorectal cancer. Colorectal cancer accounts for nine percent of new cancer cases every year worldwide. The highest incidence rates are in the developed world, while Asia and Africa have the lowest incidence rates. It remains one of the most curable cancers if diagnosis is made early.
DHA and EPA are omega-3 fatty acids commonly found in fish and fish oil. Neptune krill oil is another important source of DHA and EPA.
M.N. Hall, H. Campos, H. Li, H.D. Sesso, M.J. Stampfer, W.C. Willett and J. Ma. Blood Levels of Long-Chain Polyunsaturated Fatty Acids, Aspirin, and the Risk of Colorectal Cancer; Cancer Epidemiology Biomarkers & Prevention February 2007, Volume 16, Pages 314-321, doi: 10.1158/1055-9965. EPI-06-0346