Fish Oil and Cancer: Gene Key to Omega-3 Benefits
Omega-3 fatty acids, particularly EPA and DHA found in fish oil supplements, are popular for their anti-inflammatory properties and potential chronic disease prevention. However, their link to cancer prevention has been inconsistent, with some studies showing promise and others revealing no benefit or even increased risk.
A Crucial Gene Identified
Researchers have pinpointed a gene, ALOX15, as a key determinant in whether EPA and DHA can effectively combat colorectal cancer. This discovery, from the University of Michigan and MD Anderson Cancer Center, published in Cellular and Molecular Gastroenterology and Hepatology, suggests that assessing ALOX15 status in cancer patients might be vital for tailored omega-3 prevention strategies.
Unexpected Findings in Animal Models
Experiments with mice revealed a surprising outcome. While a standard diet showed normal tumor development, a fish oil-enriched diet actually accelerated colon tumor growth in mice exposed to inflammation-inducing chemicals. This contrasts with the body's usual conversion of EPA and DHA into inflammation-reducing compounds called resolvins, a process dependent on the ALOX15 enzyme. Notably, ALOX15 is often inactive in various cancers.
Further investigation showed that mice genetically engineered to lack ALOX15 experienced a surge in colorectal tumors when given fish oil. The extent of this effect varied based on the specific omega-3.
EPA's Edge and Supplement Forms Matter
Mice consuming diets high in EPA developed fewer tumors compared to those on DHA. The study also highlighted that certain forms of omega-3 supplements were more effective. Ethyl ester and free fatty acid forms of EPA, including those in the prescription medication Lovaza, reduced both the number and size of tumors, especially when ALOX15 was active. DHA, however, failed to prevent tumor growth in ALOX15-deficient mice.
"The source and form of fish oil are not uniform," noted Imad Shureiqi, a University of Michigan professor. "Crucially, an individual's capacity to metabolize these compounds via essential enzymes is paramount for their anti-inflammatory and cancer-preventive effects."
Implications for Patients
While these findings are primarily from animal studies, they suggest that individuals with colon polyps and inactive ALOX15 might not gain the same protective benefits from EPA and DHA. This could significantly reduce the supplements' efficacy in curbing tumor growth.
Shureiqi strongly advises patients to consult their doctors before incorporating fish oil into their regimen. The research team is now working on developing medications to enhance ALOX15 activity, aiming to improve the body's processing of omega-3s and bolster colon cancer prevention efforts.
