Roughly 19 million U.S. adults take fish oil supplements, often in hopes of lowering their risk of chronic diseases, including cancer. But new research suggests that whether fish oil actually protects against colon cancer may depend on the presence of a single gene.
Role of the ALOX15 Gene
Scientists at the University of Michigan and University of Texas MD Anderson Cancer Center discovered that the gene 15-lipoxygenase-1 (ALOX15) is essential for omega-3 fatty acids found in fish oil — EPA and DHA — to work effectively against colon cancer.
In mice lacking ALOX15, fish oil not only failed to protect but actually increased the risk of colon tumors. The findings were published in Cellular and Molecular Gastroenterology and Hepatology.
How Fish Oil Interacts With Cancer Risk
Normally, ALOX15 helps omega-3s break down into anti-inflammatory compounds called resolvins, which counteract chronic inflammation — a known driver of cancer. Without ALOX15, that protective mechanism doesn’t happen.
The study found that:
- Mice missing ALOX15 developed more colon tumors when given fish oil.
- EPA worked better than DHA, leading to fewer tumors in EPA-fed mice.
- EPA-based supplements, including the prescription drug Lovaza, reduced tumor size and number in mice with ALOX15. DHA products, however, were less effective.
Implications for Human Health
While animal study results don’t always translate directly to humans, the findings raise important questions about fish oil use. Researchers caution that fish oil may not protect everyone equally, particularly people who lack ALOX15 activity.
Dr. Imad Shureiqi, senior author of the study, noted:
“It is 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.”
Next Steps in Research
The team is now exploring drugs that can boost ALOX15 levels in cancer cells, which could improve the effectiveness of EPA and DHA in preventing colon cancer.
For now, experts recommend that patients consult their doctors before starting fish oil supplements, especially if taking them for cancer prevention.
