Fish Oil & Colon Cancer: Gene Key to Omega-3 Benefits Revealed

Nearly 19 million adults in the United States utilize fish oil supplements, seeking the benefits of their rich omega-3 fatty acid content – primarily eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). These supplements are often taken with the goal of reducing inflammation and lowering the risk of chronic diseases. However, research into the effects of omega-3s on cancer has yielded inconsistent results.

A Key Gene in Colon Cancer Protection

Researchers at the University of Michigan and the University of Texas MD Anderson Cancer Center investigated these conflicting findings. Their study, published in Cellular and Molecular Gastroenterology and Hepatology, pinpointed a gene called 15-lipoxygenase-1, or ALOX15, as a critical determinant of whether EPA and DHA can effectively suppress colorectal cancer.

Did You Know? Lovaza, a prescription medication containing ethyl ester forms of EPA and DHA, is already FDA-approved for treating high triglyceride levels.

Surprising Findings in Animal Studies

Scientists compared mice fed a fish oil-enriched diet to those on a standard diet to understand how fish oil impacts tumor development. Unexpectedly, fish oil increased the number of colon tumors in mice exposed to chemicals that promote inflammation and accelerate tumor growth.

The body typically converts EPA and DHA into resolvins, compounds that reduce chronic inflammation, a significant factor in cancer development. This conversion process depends on the enzyme ALOX15. However, ALOX15 is frequently inactive in various types of cancer.

Further research examined mice lacking ALOX15 given fish oil. The absence of ALOX15 correlated with an increase in colorectal tumors, with the effect varying based on the specific omega-3 fatty acid used.

EPA vs. DHA and Supplement Forms

Mice consuming EPA-rich diets developed fewer tumors than those given DHA. EPA and DHA are available in different forms, including free fatty acids, ethyl esters and triglycerides.

Expert Insight: The study highlights that the potential benefits of fish oil supplements are not universal and depend on an individual’s biological makeup, specifically the activity of the ALOX15 gene.

Both Lovaza, and the ethyl ester and free fatty acid forms of EPA, reduced the number and size of tumors, but only in mice with active ALOX15. DHA variants did not prevent tumor growth in mice lacking ALOX15, but did reduce growth when ALOX15 was present.

“Not all fish oil supplements are the same,” stated Imad Shureiqi, professor of internal medicine at the University of Michigan and a member of Rogel Cancer Center. “We see also important to ask whether the person who is taking the supplement has the required enzymes to metabolize these products to prevent chronic inflammation and subsequently cancer development.”

Implications for Patients

While the majority of the data originates from animal studies, the results raise important considerations. Individuals with colon polyps who do not have active ALOX15 may not experience the same protective effects from EPA and DHA, potentially diminishing the supplements’ effectiveness in slowing tumor growth.

Shureiqi recommends that patients consult with their doctors before beginning fish oil supplementation.

The research team is currently working on medications aimed at increasing ALOX15 levels in cancer cells. Their objective is to improve the body’s ability to process EPA and DHA, potentially bolstering efforts to prevent colon cancer.

Frequently Asked Questions

What did the study identify as a key factor in the effectiveness of omega-3s against colorectal cancer?

The study identified the gene 15-lipoxygenase-1, or ALOX15, as a crucial factor in determining whether EPA and DHA can help suppress colorectal cancer.

Did fish oil always reduce tumor growth in the mice studied?

No, fish oil unexpectedly increased the number of colon tumors in mice exposed to chemicals that trigger inflammation and speed up tumor growth. The effect of fish oil varied depending on whether the mice had active ALOX15 and which omega-3 fatty acid (EPA or DHA) was used.

What is the recommendation for patients considering fish oil supplements?

Patients are advised to speak with their doctors before starting fish oil supplements, as the benefits may depend on individual factors like the activity of the ALOX15 gene.

Given these new insights into the complex relationship between omega-3 fatty acids, genetic factors, and cancer development, how might personalized approaches to dietary supplementation evolve in the future?