If you’ve spent any time on wellness TikTok recently, you may have noticed that there’s an abundance of posts claiming that canola oil and other seed oils are unhealthy and should be avoided. There are a lot of videos out there making bold claims, saying that seed oils cause inflammation, or that they’re “toxic” or even “poison.”
But is this actually true?
Many of the videos don’t include sources, and some nutrition experts don’t exactly agree with all these rapidly spreading claims. To get to the bottom of the seed oil debate, we reached out to leading physicians and registered dietitians.
Keep reading for everything you need to know about seed oils, including whether you need to ditch them.
First things first: What are seed oils?
Seed oils are a category of plant-based oils made from the seeds of plants. Some of the most common seed oils are soybean, grapeseed, sunflower, safflower and canola (also known as rapeseed).
“Seed oils are made by grinding, pressing and heating plant seeds to high temperatures so that the fatty acids they contain oxidise and their oils can be extracted,” explained Maddie Pasquariello, a registered dietitian. Seed oils are commonly used in packaged foods on grocery store shelves, in commercial food production, and in the restaurant and food service industries.
One reason seed oils are used in so many different foods is that they often have a mild flavour and aroma.
Are seed oils actually bad to consume?
This question isn’t as cut and dry as one might expect.
“Seed oils can be a healthy part of a diet, especially if the consumption of these oils are in conjunction with adequate intake of omega-3 fatty acids, like those that come from oily fish or walnuts,” said Lauren Manaker, a registered dietitian.
At the same time, it’s also true that many foods made with seed oils, such as ultra-processed foods and fried foods, are not beneficial for human health, said Ashley Kitchens, a registered dietitian. But this doesn’t necessarily mean seed oils are causing problems. Highly processed foods often contain large amounts of sodium, sugar and refined carbohydrates, which can cause health issues when consumed in excess.
“It would be more beneficial for your health to focus your efforts on reducing your intake of these types of ultra-processed and fried foods, versus focusing just on seed oils,” Kitchens said.
Is it true that there are risks to consuming seed oils that have been heated?
Seed oils are often heated to high temperatures for deep frying and other purposes when making highly processed foods — and this isn’t great for human health. Seed oils that contain large amounts of an omega-6 fatty acid called linoleic acid generate a compound called hydroxynonenal when heated to a high temperature beyond their smoke point. Ingesting this compound can lead to health problems like impaired energy metabolism and increased oxidative stress.
But this doesn’t mean you can’t heat seed oil when cooking at home.
“The amount you’re cooking with at home is likely much more negligible, and you’re unlikely to experience poor health simply because this is one ingredient you use in cooking,” Pasquariello said.
Do seed oils cause inflammation?
Seed oils contain varying amounts of omega-3 and omega-6 fatty acids, which are both polyunsaturated fats considered healthy. The amount of omega-3 and omega-6 fatty acids vary from one seed oil to the next. For example, flaxseed oil contains a high amount of omega-3 fatty acids, while sunflower and soybean oils have higher amounts of omega-6 fatty acids, and palm kernel oil contains just trace amounts of omega-3 fatty acids, Kitchens said. The body needs fatty acids, but can’t make them on its own, so they must come from food sources.
While we need omega-6 fatty acids, there is concern that these fatty acids, when consumed in high amounts, may lead to inflammation, said Dr. Christina Tennyson, a board-certified gastroenterologist at Augusta Health.
“Nutrition studies are notoriously difficult to perform and interpret, so I think the jury is still out as far as the current research is concerned,” Tennyson said.
“There is some concern about the ratio in refined seed oils of omega-6 to omega-3 fatty acids, with omega-6 fatty acids thought to be pro-inflammatory, but the significance of this is unclear,” said Dr. Linda Shiue, the director of culinary and lifestyle medicine at Kaiser Permanente San Francisco.
One point to keep in mind in the meantime is that you don’t need to include seed oils in your diet just to make sure you’re getting enough of these important fatty acids.
“Whole soybeans, nuts, seeds, fish, and eggs will likely be more beneficial sources of omega-6 fatty acids when looking at their complete nutritional profile, compared to just consuming oil,” Pasquariello said. “So, I’d advise folks to try adding these alternative food sources of fat first, if adding additional omega-6 fatty acids is recommended to them.”
Are there nutritional benefits to seed oils?
Seed oils offer a variety of healthy fats and can be a good swap for products that are higher in saturated fats.
“Studies show that omega-3 rich oils may protect against certain types of cancer and improve heart health,” Kitchens said.
Additionally, omega-6 fatty acids may reduce the risk of cardiovascular disease, according to the American Heart Association. To improve cardiovascular outcomes, clinical guidance generally recommends substituting sources of saturated fat — like butter, coconut oil, palm oil, bacon grease and sausage — with sources of polyunsaturated fat, like walnuts, flax seeds, fish and most seed oils, including canola, soybean, safflower, and grapeseed, Pasquariello said.
Does this mean you should go out of your way to incorporate more seed oils into your diet? Probably not.
“Fats are still high in calories — 9 calories per gram, compared to the 4 calories per gram found in carbs and protein sources — and seed oils are indeed a component of many foods that are less nutritionally dense,” Pasquariello said.
In moderation, seed oils are probably fine to consume, especially if you’re cooking with them at home. You don’t need to avoid them at all costs, as some TikTok videos would lead you to believe, but you also don’t need to go out of your way to eat more of them. Consuming whole foods like walnuts, sunflower seeds, peanut butter, edamame, chia seeds, almonds, and hemp seeds is a great way to get your fatty acids.
“In the context of a healthy diet comprised mainly of plants in whole form, seed oils consumed in moderation — the small amounts used for cooking — are unlikely to cause harm,” Shiue said. “I am more concerned about diets high in ultra-processed food and added sugars, both of which have better evidence for causing negative health outcomes and chronic diseases.”