Just when you thought you’d figured out the good guys and bad guys in the grocery store aisle, along comes the seed oils controversy. Seed oils are blamed for heart disease, cancer, weight gain and other chronic diseases linked to inflammation. Hash tags #seedoiltoxins #seedoilpoison are trending on Instagram. We decided to take a closer look at these claims.
Things came to a head in 2020. Prominent podcast Joe Rogan did a 3-hour interview discussing the health dangers of seed oils. That same year Dr. Cate Shanahan, whose practice focuses on nutrition and human metabolism, wrote the blog, the “The Hateful Eight.” It singled out seed oils popular in many pantries: canola, corn, sunflower, safflower, soy, grapeseed, rice bran and cottonseed. Dr. Shanahan stated that the high levels of polyunsaturated fatty acids in seed oils promote inflammation and the accumulation of toxins in body fat, as well as other chronic health conditions.
Controversy over Omega-6s
Seed oils, which are made from plant seeds, are popular with chefs because they have a neutral taste and high smoke point. This means they don’t burn easily in cooking and baking. They contain saturated, monounsatured and polyunsaturated fats. The polyunsaturated fats include the healthy omega-3 fatty acids which are found in fish and nuts. They also contain omega-6 fatty acids, which are found in many vegetables and is important for healthy development. However, too much of omega-6 is known to cause inflammation and some studies even link it to cancer or cardiovascular or other chronic diseases. Some studies say healthy issues arise when the ratio of omega-6s far outweighs omega-3 fatty acids.
History of seed oils
Seed oils are relatively new to the human diet. Before they arrived, people only ate natural fats including olive oil, coconut oil, butter and ghee, lard and suet. In 1961 the American Heart Association (AHA) recommended polyunsaturated fatty acids (PUFAs) to replace saturated fats, which they linked to heart disease. Critics say it was only after the introduction of PUFAs that heart disease became a leading cause of death in the United States.
Harvard: Processed food, not the seed oils to blame
Several medical researchers including Harvard don’t agree with Dr. Shanahan. In Scientists Debunk Seed Oils Health Risk, Guy Crosby, an adjunct associate of nutrition at Harvard T.H. Chan School of Public Health, says that the claims are unsubstantiated. He acknowledges that seed oils are found in many processed food or fried foods, laden with carbohydrates, sugar and sodium. But he argues that avoiding processed foods could solve the issue.
Seed oils are often used in commercial deep fryers and if the oil isn’t frequently changed, it could lead to health issues. (Repeated reheating of cooking oil causes it to change composition and release acrolein. This is a toxic and potentially carcinogenic chemical. Restaurants will often reheat the same oil multiple times.) He also asserts that this is a non-issue for home cooks using seed oils.
And finally, he argues that there’s nothing wrong with omega-6 fatty acids. Our body relies on them for bone health, reproductive health, brain function and metabolism.
Higher in calories
We reached out to frequent Smart Lifebites contributor Lisa Young, PhD, RDN Nutrition consultant and author of Finally Full, Finally Slim. “I agree with Harvard,” Young said. “Nut oils in moderation are fine. However, you are best with natural oils like extra virgin olive oil or avocado oil, and I’d suggest that you not overheat the oils.”
“All fats contain the same number of calories,” she continues, “so they can equally lead to weight gain. You are always better off skipping the refined ultra-processed foods.”
What if you still want to avoid them?
Even if you exclusively cook with olive oil, you might be unknowingly consuming seed oils. “Healthy” granola bars, salad dressings, baked chips and cookies all contain seed oils. Even breads might contain seed oils. But you can still take a few steps to lower the amount in your diet. Here are few things to try:
- Coconut oil, extra virgin olive oil, butter or ghee are all good alternatives.
- Of all the animal fats, try duck fat. It contains 65 percent unsaturated fat, a fat profile similar to olive oil and a high smoke point.
- Read food labels and try to buy more that contain omega-3s and monounsaturated fats.
- Make your own salad dressings with extra virgin olive oil and vinegar or lemon juice.
- Avoid fried foods, especially when dining out.
Patty Yeager is the managing editor of Smart Lifebites. Her stories include: No Excuses Guide for Starting a Vegetable Garden and 5 Cool things you probably didn’t know about pecans.