No, cooking oil doesn't cause cancer — but new study links too much seed oil to colon tumors

Cooking oils come in many varieties, such as canola oil, olive oil, coconut oil, and others. The health benefits and drawbacks of these oils often spark discussions online, particularly concerning their potential link to cancer risk.

Studies indicate that nutritious cooking oils, such as avocado and olive oil, provide numerous advantages, including better heart health and even a lower risk of cancer. However, seed oils like canola, corn, and sunflower are frequently criticized. It's important to point out that many prominent health organizations and professionals maintain that these oils can be part of a healthy diet when consumed in moderation.

A recent study has reignited concerns about the potential cancer risks associated with cooking oils. Dr. Timothy Yeatman, a surgical professor at the University of South Florida and a member of Tampa General Hospital’s Cancer Institute, shared with TODAY.com his worries regarding the high intake of seed oils, particularly those found in heavily processed foods. However, he clarified that the findings of the study do not actually indicate that cooking oils, including seed oils, are direct causes of cancer.

The concern regarding seed oils and cancer arises from their high levels of omega-6 fatty acids, which research suggests may contribute to inflammation in the body. Therefore, it’s crucial to maintain a balance between omega-6 and omega-3 fatty acids, as the latter are known for their anti-inflammatory properties. Experts at Mount Sinai recommend aiming for a dietary ratio of omega-6s to omega-3s that falls between 2:1 and 4:1.

Omega-6 and omega-3 fatty acids are forms of unsaturated fats that are good for your heart. This is why the American Heart Association recommends including seed oils in a balanced diet. Omega-6 fatty acids can be found in various foods, including nuts, which offer additional health advantages. Omega-3 fatty acids are commonly present in fish, as well as in certain seeds and nuts.

On the other hand, seed oils are commonly found in highly processed foods, which have been repeatedly associated with a higher risk of cancer.

Here’s what you need to understand about the research, cooking oils, and cancer.

Study Links Excess Seed Oils To Colon Cancer Risk

The research, carried out in a laboratory supported by the National Cancer Institute, examined how lipids, or fats, influence the surroundings of colon cancer tumors.

Specifically, the focus was on lipid mediators, which are a kind of fat that plays a crucial role in how cells communicate with one another in the body. These lipid mediators mainly come from the dietary fats consumed by an individual, according to Yeatman, who also serves as the assistant director for translational research and innovation at the Cancer Institute of Tampa General Hospital.

In their research, scientists examined the colon cancer tumors from 81 individuals utilizing a device known as a mass spectrometer. This equipment allowed them to identify the various kinds of lipid mediators present in the tumors and to measure the precise amounts of each type.

Yeatman and his team discovered that nearly all of the lipid compounds found in the tumors belonged to the "pro-inflammatory" category, like omega-6 fatty acids. This indicates that these compounds encourage inflammation and weaken the immune response in the tumor's vicinity, according to Yeatman. In contrast, there were very few, if any, lipid compounds from the "pro-resolving" category, such as omega-3 fatty acids, which help lessen inflammation in the tumors.

Research has shown that inflammation can play a role in the development of some types of cancer, including colon cancer, according to Yeatman. His work builds on this understanding by proposing that certain foods may cause lipid mediators which inhibit the immune cells surrounding tumors, thereby facilitating their growth.

"Consuming too much omega-6 can lead to an increase in substances that promote inflammation, creating an environment in the colon that dampens the immune response against cancer. This, in turn, may enable cancer cells to thrive and spread," Yeatman explains.

Should You Stop Using Cooking Oils And Seed Oils?

You certainly shouldn't eliminate cooking oils, including seed oils, based on this research, according to Yeatman. He emphasizes that olive oil is packed with health advantages and plays a vital role in the Mediterranean diet, which is widely regarded as the most healthful way of eating. Similarly, avocado oil also supports heart and eye health, among other benefits.

The issue of seed oils is somewhat complex, but Yeatman maintains that using them in moderation can be beneficial. Omega-6 fatty acids are essential for the body’s proper functioning. However, he advises against overindulging in seed oils and processed foods that have high amounts of these oils, especially in comparison to foods rich in omega-3 fatty acids.

"I'm not criticizing seed oils," Yeatman explains. "However, when you consume them for breakfast, lunch, and in your salad dressing for dinner, it accumulates and that’s where the issue lies."

Dr. Nate Wood, who leads the culinary medicine program in the internal medicine department at Yale School of Medicine, shared with TODAY.com that he typically has two types of cooking oil on hand: extra virgin olive oil and canola oil, the latter being a seed-based oil.

He emphasizes that studies indicate it's the seed oils present in ultra-processed foods that are linked to inflammatory reactions leading to colon cancer and other types of cancer, rather than simply using seed oils in cooking.

Dr. Suneel Kumath, a gastrointestinal cancer specialist at the Cleveland Clinic, believes the research indicates that consuming too much seed oil, which disrupts the balance between omega-6 and omega-3 fatty acids, might be connected to colon cancer. However, he also points out that various other health factors could be involved when someone has a diet high in omega-6s and low in omega-3s, or the opposite. In short, while the study suggests a link between high levels of omega-6s and colon cancer, it does not prove that one causes the other.

The Real Issue: Seed Oils In Processed Foods

All three specialists share the same conclusion from the research: it's important to reduce your intake of processed foods, which often contain seed oils.

According to Yeatman, the recent surge in colon cancer cases among younger individuals corresponds with a significant rise in the consumption of processed foods.

"We should recognize that products with a long list of ingredients are often not the healthiest choice," he continues. "If anyone is looking for guidance, they should begin by checking the labels."

Wood emphasizes that he doesn't worry about using seed oils in cooking. "My main concern is with the highly processed foods that contain these seed oils. ... We need to keep pushing this message because many people aren't ready to accept it. They prefer to point fingers at the seed oils instead."

Although the studies regarding colon cancer and omega-6 fatty acids can be intricate, the message for maintaining a healthy lifestyle is clear. Kamath points out, "The foods rich in omega-3 fatty acids are already recognized as the best choices for our diet."

Maura Hohman serves as the senior health editor for TODAY.com and has been reporting on health and wellness topics since 2015.