Fatty Acids and Colorectal Cancer: Why the Research Is So Complicated

This review looked at how different types of fatty acids—saturated, monounsaturated, omega-6, and omega-3—relate to colorectal cancer risk and outcomes. Instead of finding simple patterns, the researchers found that the relationship depends heavily on how fat exposure is measured: what people eat, what shows up in their blood or red blood cells, what’s found in tumor tissue itself, or what genetic studies predict.

The review challenges the common idea that saturated fats and omega-6 fats are always bad, monounsaturated fats are neutral, and omega-3 fats are always protective. Instead, effects varied by the specific fatty acid, its food source, the body tissue studied, individual metabolism, tumor location, sex, and cancer stage.

Some encouraging findings came from blood-based omega-3 biomarkers, including a large prospective UK Biobank study showing inverse associations with colorectal cancer, though these patterns weren’t always straightforward and differed by cancer site and sex. Genetic studies (Mendelian randomization) offered supporting but imperfect evidence, and cancer tissue itself showed altered fat profiles, though this can’t prove what caused the cancer. Clinical trials of fatty acid interventions showed some benefits for recovery after surgery, inflammation, and nutritional status, but there wasn’t strong evidence yet that fatty acid interventions prevent precancerous polyps, cancer recurrence, or improve survival.