Cooks around the world use seed oils such as canola, sunflower and grapeseed for their neutral taste and higher smoke point. Yet, a growing number of social media influencers, posters on forums, politicians and podcasters have claimed that they’re “toxic.” Robert F. Kennedy Jr., Donald Trump’s choice for leader of the United States Department of Health and Human Services, has recently resurfaced the argument, urging people to “Make Frying Oil Tallow Again,” selling T-shirts, hats, dog bandanas and car magnets with the slogan in his merch store.
Critics have linked consuming seed oils to various ailments, from headaches and inflammation to obesity and heart disease. Kennedy posted on X that Americans are being “unknowingly poisoned” by seed oils. But are they?
Health experts say the assertion that seed oils are harmful to your health is “flawed.” As Christopher Gardner, a professor of medicine at Stanford University, told the American Heart Association, seed oils “are not to be feared.” One of the anti-seed oil movement’s claims is that the omega-6 fatty acids in seed oils convert into toxins when cooked, leading to inflammation and chronic illnesses. Gardner said this argument “is flawed in numerous ways.”
Polyunsaturated fats such as omega-6 and omega-3 can help lower “bad” (LDL) cholesterol levels, reducing the risk of heart disease and stroke. Though omega-3s do this more effectively, “that doesn’t mean omega-6 is bad for you,” said Gardner.
Rather than the seed oils themselves, Gardner said the “real concern” is high consumption of ultraprocessed foods. Highly processed packaged snacks and ready-to-eat meals often contain seed oils as well as refined carbohydrates, sodium and sugar. “It’s hard to cast the blame on the seed oils when these foods contain so many other things.”
When it comes to consuming omega-6s, “It’s all about the ratios,” said Raysa El Zein, a lecturer at the University of Westminster. Most Westerners eat more omega-6s than omega-3s (sometimes, at as high a ratio as 15:1), which can lead to inflammation, El Zein writes in The Conversation. “As long as people consume enough omega-3, the consumption of omega-6 would not cause inflammation. In fact, their combined intake would reduce the risk of several chronic diseases, such as heart disease and diabetes.”
Critics of seed oils, such as Canadian canola, the most-imported oil in the United States, often take issue with how they’re produced. Seed oils undergo an extraction process rather than being pressed like olive oil. When cooking at home, using a seed oil such as sesame in a vegetable stir-fry, for example, the benefits “far outweigh any potential health risks,” said Gardner.
Guy Crosby, an adjunct associate of nutrition at Harvard T.H. Chan School of Public Health, echoed this sentiment, telling Consumer Reports in 2022, “Cooking with seed oils at home isn’t an issue.” Crosby identified the “main problem” as restaurant and factory deep-fryers reusing and reheating seed oils, causing them to degrade. As El Zein also points out, trans fats can form in recycled oil, which “increase ‘bad cholesterol’ and decrease ‘good cholesterol.’”
When it comes to swapping seed oils for tallow (rendered fat typically made from beef suet) or other saturated fats, such as butter and lard, Alice H. Lichtenstein, a professor of nutrition science and policy at Tufts University, told The New York Times that “would be a mistake.”
Health associations, including the Heart and Stroke Foundation of Canada and the American Heart Association, suggest consuming polyunsaturated fats such as canola and sunflower oils in moderation. According to the American Heart Association, “The ‘bad’ fats — saturated fats and trans fats — can negatively affect your health.”
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