Are Seed Oils Bad for You?

These findings were supported by a study, published in AMA: The Journal of the American Medical Association in spring 2025, of three large cohorts of patients (including two Nurses’ Health Studies covering 33 years). The study linked higher butter intake to a higher risk of death and higher intake of plant-based oils (canola, soybean and olive) to a lower total mortality. 

And a review published in October 2024 in the British Journal of Nutrition emphasized seed oils’ link to a lower risk of cardiovascular disease and type 2 diabetes, concluding that they do not lead to increased inflammation.

“Specifically, vegetable oils rich in UFA [unsaturated fatty acid] should be consumed instead of rich sources of SFA [saturated fatty acid], such as butter, tallow, lard, palm and coconut oils, duck fat and ghee,” the study said.

Seed oils and inflammation

As for the notion that omega-6s promote inflammation, Gardner says that social media seems to have concluded that because omega-3s are more anti-inflammatory than omega-6s, that means omega-6s are pro-inflammatory. In fact, both omega-6s and omega-3s are anti-inflammatory, he says. 

Furthermore, a 2017 meta-analysis found that increasing linoleic acid intake did not have a significant impact on inflammation. 

Other critics say that even if omega-6’s are good for us, the greater than 10-to-1 ratio in the Western diet of omega-6s to omega-3s is out of whack. But according to the Academy of Nutrition and Dietetics, there is no definitive evidence of what the best ratio is. 

In any case, says Marklund, “to change this ratio, you should probably increase your omega-3s from foods like fish because both omega-3s and omega-6s are beneficial, especially for cardiovascular disease. They have different actions in our body.”

Cooking with seed oils at high temperatures

Questions have also been raised about the safety of cooking with oils at high temperatures or reheating them. But most seed oils have high smoke points (from 408 degrees Fahrenheit for refined sunflower oil and up to 445 degrees for refined canola), so “in the general cooking you do at home, there’s no danger,” says Marklund.

Studies have found that cooking for long periods or reheating oil numerous times can generate dangerous trans-fatty acids, but that doesn’t happen in the kind of cooking people do at home, he adds.

Another criticism of seed oils is that they are helping to fuel the obesity epidemic in this country. This likely stems from the fact that seed oils are commonly used in the ultra-processed foods that have become a staple of the American diet. A Johns Hopkins analysis found that more than half of the calories we consume at home come from ultra-processed foods.

And that’s not good for us. An August 2025 science advisory from the American Heart Association advises that most ultra-processed foods — which include sugary drinks, ultra-processed meats, refined grains, candy and commercial baked goods — have poor nutritional quality. Such foods include saturated fats, added sugars and sodium. 

Nutrition experts agree that these foods are bad for our health, but seed oils are not the problem. “It’s not just one food. It’s not just seed oils. Or sugar. Or saturated fat,” says Julia Zumpano, a dietitian at the Cleveland Clinic. “It’s the whole picture. Most people aren’t putting seed oil in a cup and drinking it. It’s in a cracker, a dressing, a candy or protein bar, a coffee cream — the list goes on and on. So look at ingredient labels.”

Hexane in seed oils

And what about hexane, a much-maligned solvent used in the processing of seed oils and many other foods? In high levels, it is unhealthy to breathe and ingest, causing neurotoxic ailments ranging from depression to headaches.

But hexane is almost entirely distilled off the seed oils you pick up on your grocery shelf. “Residual amounts are very minimal, very minute,” says dietitian Maureen Ashbarry, “and the amount that remains is not considered harmful. It’s below the levels deemed significant by our food authorities.”

Still, if you want to avoid hexane entirely, look for “expeller-pressed” or “cold-pressed” seed oils, which are extracted without the use of chemicals, the way extra virgin olive oil is made.

The bottom line: You don’t need to throw away that bottle of canola, corn or other seed oil (or the very healthy extra-virgin olive oil or avocado oil) in your pantry. “It’s OK if you make muffins with canola oil or sauté your vegetables in sunflower oil,” says Tara Schmidt, lead registered dietitian at the Mayo Clinic.

In short, be sensible. “I generally advise a whole foods diet,” says Zumpano. “I encourage fruits and vegetables, whole grains, nuts and seeds, fish, lean meats and legumes. Processed foods can’t be completely avoided, but we want to minimize them.”  

Olive oil vs. seed oils

Olive oil is not a seed oil because the oil is derived from a fruit and not a seed. It is a vegetable oil, as are seed oils. Numerous studies have found that olive oil is particularly healthy. It’s the oil used in the Mediterranean diet, which is especially healthy for the brain. People who regularly consume olive oil have a lower risk of heart disease, cancer, neurodegenerative diseases and early death.