More Omega-3 & Less Omega-6 for Colorectal Protection
Lee Swanson Research Update
Researchers have determined that increasing the intake of omega-3 fatty acids and decreasing intake of omega-6 could reduce the risk of colorectal cancer.
The highest dietary ratio of omega-6 to omega-3 was associated with a 95% increase in the risk of women developing colorectal cancer, according to results of a study with 73,242 Chinese women participating in the Shanghai Women's Health Study.
The study, published in this month's issue of Cancer Epidemiology Biomarkers & Prevention, adds to a growing body of evidence supporting the importance of balance between omega-3 and omega-6 fatty acids. Previously, the ratio of omega-3 to -6 has been linked to prostate cancer risk.
According to Harvey Murff from Vanderbilt University and his co-workers, data on how polyunsaturated fatty acids (PUFA) may impact the risk of colorectal cancer have been "inconsistent."
Using data derived from two food frequency questionnaires, Murff and his co-workers investigated if PUFA intake could impact colorectal cancer risk in Chinese women.
Their findings suggested that "the dietary total omega-6 to omega-3 PUFA ratio was strongly associated with colorectal cancer risk." Indeed, increasing ratios of omega-6 to omega-3 were associated with increased risks of colorectal cancer. Compared to women with the lowest ratio, women with the highest ratio of omega-6 to -3 had a relative 95% higher risk.
The omega-6 fatty acid arachidonic acid (AA) was also linked to an increased risk of colorectal cancer. Specifically, women with the highest average intakes had an associated risk 40% higher than women with the lowest average intakes.
Previously, researchers from other groups have proposed the role of metabolites of omega-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), and the omega-6 acid arachidonic acid as playing an important role in carcinogenesis. These three fatty acids compete to be converted by cyclooxygenase enzymes (COX-1 and COX-2) into prostaglandins, which can become either pro-inflammatory and increase tumor growth, or anti-inflammatory and reduce growth.
Indeed, in a subset of 150 cancer cases and 150 healthy controls, the researchers noted that an increasing omega-6 to omega-3 ratio is linked to increased levels of the pro-inflammatory prostaglandin E2 (PGE2).
"These results suggest that dietary PUFA and the ratio of omega-6 to omega-3 PUFA intake may be positively associated with colorectal cancer risk, and this association may be mediated in part through PGE2 production," concluded Murff and his co-workers.
Cancer Epidemiology Biomarkers & Prevention 18(8):2283-2291, 2009