Study links common cooking oils from corn and sunflower seeds to increased colon cancer risk

The foods we eat might be influencing our body’s ability to fight off cancer, particularly colorectal cancer, according to a groundbreaking study published in Gut, the journal of the British Society of Gastroenterology.

Researchers have identified a troubling link between high levels of omega-6 fatty acids in modern diets and an increased risk of inflammation that may promote tumor growth, especially in the colon.

Omega-6 fatty acids, commonly found in seed oils like soybean, corn, and sunflower, are prevalent in ultra-processed foods that dominate the Western diet. These fats are essential for health, playing roles in skin and hair growth, metabolism, and bone health. However, when consumed excessively, omega-6s can be converted into molecules that promote prolonged inflammation—a key factor in cancer development.

“Our bodies are constantly experiencing mutations in the gastrointestinal tract, and the immune system, with the help of molecules derived from omega-3 fatty acids, typically eliminates these threats,” Dr. Timothy Yeatman, senior coauthor of the study and surgical oncologist at the Tampa General Hospital Cancer Institute, said to CNN. “But when there is a chronic imbalance—too much omega-6 and too little omega-3—the body’s defenses falter, allowing mutations to take hold and tumors to thrive.”

Modern diets aren’t helping

The imbalance of omega-6 to omega-3 fatty acids is stark in many modern diets. Historically, humans consumed these essential fats in roughly equal proportions. However, the rise of industrialized food production has skewed this balance.

Over the past half-century, the amount of omega-6 in American diets has surged by 136%, largely due to the widespread use of inexpensive seed oils in fried and packaged foods. Conversely, the intake of omega-3—found in fatty fish, flaxseeds, and walnuts—has diminished significantly, as dietary patterns shifted away from fresh, nutrient-rich foods.

Cancer rates are rising

The shift toward ultra-processed foods and away from traditional diets has had devastating consequences for public health. Colorectal cancer, once rare in younger populations, is now on the rise among individuals under 50. Millennials have twice the risk of colorectal cancer compared to those born in 1950, according to a 2017 study. Factors like rising obesity rates, reduced physical activity, and changes in gut microbiota due to processed foods all contribute to this trend.

Mounting evidence suggests that ultra-processed foods, high in omega-6-rich oils and low in omega-3s, are a significant driver of this risk. “We’re not saying omega-6 is inherently bad,” Yeatman said to CNN. “The problem lies in the imbalance. Our ancestors’ diets provided the right proportion of these fats, but modern convenience foods have upset this delicate equilibrium.”

How to reduce cancer risk

To reduce cancer risk and promote overall health, experts recommend increasing omega-3 intake while moderating omega-6 consumption. The American Heart Association suggests eating two servings of fatty fish, such as salmon or mackerel, per week. Plant-based sources of omega-3, like flaxseeds and walnuts, can also help restore balance. Limiting ultra-processed foods and choosing whole, minimally processed options are key steps toward achieving a healthier dietary pattern.