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

Cooking oils include a wide range of products, from canola oil to olive oil, coconut oil and more. The nutritional pros and cons of cooking oils are a frequent subject of debate online, especially whether they may increase the risk of cancer.

Research shows healthy cooking oils like avocado and olive oil offer a range benefits, from improving heart health to, yes, reducing cancer risk. But seed oils in particular, such as canola, corn and sunflower, are often vilified — though it’s worth noting many leading health organizations and experts say they’re healthy to consume in moderation.

A new study is again stirring up fears that cooking oils may cause cancer. And while the lead author — Dr. Timothy Yeatman, professor of surgery at the University of South Florida and Tampa General Hospital’s Cancer Institute — tells TODAY.com that he has concerns about high consumption of seed oils, especially from ultraprocessed foods, the results do not show that cooking oils, including seed oils, cause cancer.

The question of seed oils and cancer started because seed oils are high in omega-6 fatty acids, some of which may promote inflammation in the body, research has shown. So, it’s important to balance omega-6s with getting enough omega-3 fatty acids in the diet, which are considered anti-inflammatory. General nutrition guidance recommends a dietary ratio of between 2:1 and 4:1 omega-6s to omega-3s, according to Mount Sinai.

Both omega-6 and omega-3 fatty acids are types of unsaturated fats, beneficial for heart health. That’s why the American Heart Association says seed oils can be part of a healthy diet. Omega-6s are also found in foods with other health benefits, such as nuts. Omega-3s are often found in fish, as well as some seeds and nuts.

However, seed oils are also frequently used in ultraprocessed foods, which have been consistently been linked to increased cancer risk.

Here’s what to know about the study, seed oils and cancer.

New study finds possible link between excess seed oil and colon cancer

The study, conducted in a lab funded by the National Cancer Institute, focused on the role of lipids, also known as fats, in the microenvironments around colon cancer tumors.

In particular, it looked at lipid mediators, a type of lipid responsible for communication between cells in the body and which is largely derived from the fats a person eats, explains Yeatman, who is also assistant center director for translational research and innovation at the Tampa General Hospital Cancer Institute.

For the study, researchers analyzed the colon cancer tumors of 81 people using a tool called a mass spectrometer, which was able to determine which types of lipid mediators and the exact quantity of each were present in the tumors.

Yeatman and his team found that most, if not all, of the lipid mediators in the tumor were of the “pro-inflammatory class” of lipids, such as omega-6 fatty acids, meaning they promote inflammation and suppress the immune system around the tumor, Yeatman explains. There were few, if any, “pro-resolving class” lipid mediators, such as omega-3s, which reduce inflammation, present in the tumors.

It’s been established that inflammation can contribute to developing certain cancers, such as colon cancer, Yeatman says. So essentially, his research adds to this knowledge, suggesting that consuming certain foods may lead to lipid mediators suppressing the immune cells around the tumors, allowing them to grow.

“(Eating) excess omega-6s results in excess pro-inflammatory lipid mediators, which results in an immuno-suppressed environment of the colon cancer. And I think it allows it to grow and prosper and propagate,” Yeatman explains.

Should you stop eating cooking oils? What about seed oils?

No, you should not stop eating cooking oils, or even seed oils, in response to this research, Yeatman says. In fact, olive oil has numerous health benefits and is a central component in the Mediterranean diet, consistently shown to be the healthiest eating pattern, Yeatman points out. Avocado oil, too, has benefits for heart and eye health and more.

While the question of seed oils is a little more complicated, Yeatman still says that eating seed oils in moderation is healthy. In fact, omega-6s are necessary to keep the body functioning. But he discourages consuming far more seed oils and processed foods containing seed oils than those containing omega-3 fatty acids.

“I’m not demonizing seed oil,” Yeatman says. “But when you eat it at breakfast, at lunch, and in your salad dressing at dinner, it adds up and that’s the problem.”

Dr. Nate Wood, director of culinary medicine in the department of internal medicine at Yale School of Medicine, tells TODAY.com that he keeps two cooking oils in his cabinet: extra virgin olive oil and canola oil, which is a seed oil.

He stresses that research shows that it’s the seed oils found in ultraprocessed foods that are contributing to inflammatory responses that lend to colon and other cancers, not just cooking with seed oils.

Dr. Suneel Kumath, a gastrointestinal oncologist at Cleveland Clinic, agrees that the study seems to show that excess consumption of seed oils that puts the omega-6 to omega-3 ratio out of whack may be linked to colon cancer — but he adds that other health factors may be at play when you eat too many omega-6s and too few omega-3s and vice versa. So essentially the study shows a correlation between excess omega-6s and colon cancer, but not causation.

The real problem is seed oils in ultraprocessed foods

All three experts agree that the main takeaway of the research is to eat less processed food, where seed oils are frequently found.

In fact, the recent rise in colon cancer in young people aligns with a dramatic increase in processed food consumption, Yeatman says.

“We need to … understand that things with a thousand ingredients aren’t very good for you,” he adds. “If people want advice, they should start reading labels.”

Wood reiterates that he’s not concerned about cooking with seed oils. “I’m concerned about the ultraprocessed foods that the seed oils are found in. … We have to continue driving (that) in because folks are not ready to hear it. They just want to blame the seed oils.”

While the research on colon cancer and omega-6s may be complex, the implications for living a healthy lifestyle are not, Kamath says: “The foods that are high in omega-3s … are already known to be the right things we should should be eating.”

Seed oils list

Again, it’s important to note that seed oils themselves aren’t unhealthy when consumed in moderation, like most foods, the experts say. They pose the greatest health risk in a diet high in ultraprocessed foods.

These are some of the most common seed oils, according to Cleveland Clinic:

• Canola oil, also known as rapeseed oil

• Cottonseed oil

• Grapeseed oil

• Sesame oil

• Soybean oil

• Sunflower oil

• Safflower oil

• Rice bran oil

• Peanut oil

Healthiest cooking oils

Yes, cooking oil can be part of a healthy diet, the experts say, and many of the most common types of cooking oils have health benefits.

When cooking with oil, try to choose one with less saturated fat, that’s unrefined and from nontropical fruits, vegetables nuts or seeds, TODAY.com previously reported.

Here are some of the healthiest cooking oils when consumed in moderation:

This article was originally published on TODAY.com