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The Truth About Seed Oils According to a Dietitian

March 04, 20243 min read

“Canola oil is toxic!”

“Seed oils are inflammatory!”

“Industrial seed oils are making us sick!”

If you have been on Instagram, Facebook, Twitter, or TikTok lately, you have probably seen posts or memes claiming that seed oils are toxic. Seed oils are blamed for health issues including headaches, foggy thinking, lowered immunity, heart disease, and type 2 diabetes.

On the other hand, you’ll see claims about the benefits of seed oils, from cholesterol lowering to blood sugar regulation and more.

As a registered dietitian, I can help get to the bottom of this controversy. What does real science say?

In this blog post, we’ll discuss what seed oils are and what impact they may have on your health.

What are seed oils?

While you might be hard-pressed to name more than one seed oil, they’re actually more common in our food system than you’d guess. Examples of seed oils include:

  • canola

  • sunflower

  • cottonseed

  • safflower

  • rice bran

  • grapeseed

Soy and corn oils are also characterized as seed oils as well even though they don’t come from seeds.

Even though you might not have cottonseed oil in your shopping cart, I’ll bet that you have seed oils in the foods that you buy, either at the grocery store or from restaurants. Seed oils are found in many common processed foods including French fries, chips, doughnuts, and salad dressings.

What is the concern?

According to some influencers, seed oils have high levels of polyunsaturated fatty acids (PUFAs), specifically omega-6 fatty acids, that promote inflammation, the accumulation of toxins in body fat, and other chronic health conditions.

There are also questions about how these oils are processed. Some oils come from genetically modified (GMO) plants including soy, corn, cottonseed, and canola. GMOs are not fully understood and there are many concerns including organ toxicity, genetic mutations, antibiotic resistance, and cancer risk.

The process of producing seed oils is also questionable. After the seeds are harvested, they are heated to extremely high temperatures that oxidize the fatty acids creating toxins that are thought to cause health issues. Foods that are cooked with seed oils contain even higher levels of toxins, according to anti-seed oil advocates.

What does science say about seed oils?

Science does not support the claims that seed oils cause health issues. While it is true that some seed oils contain more omega-6 fatty acids, which are thought to cause inflammation, these oils are not harmful. In fact, omega-6s can reduce your risk for heart disease by lowering harmful LDL cholesterol.

Research to date has not shown that GMOs are harmful from a health perspective. However, this may change in the future as technology develops and becomes more sophisticated. So, stay tuned.

In terms of cooking with oils, it is true that some oils can handle heat better than others. Smoke point refers to the temperature at which oil starts to break down, losing some of its nutritional value and causing a bitter unpleasant taste to food. Heating an oil at too high of a temperature for too long can cause these issues, but doesn’t release the so-called “toxins.” To help you decide which oil to use when cooking, learn more here.

The bottom line

Seed oils can fit into a healthy diet.

Rather than avoiding seed oils, focus on limiting the saturated fats in your diet (butter, full-fat dairy products, fatty cuts of meat, and coconut oil). Choose oils rich in omega-6 as well as omega-3 fatty acids.

Good sources of omega-6 fats include:

  • safflower oil

  • sunflower oil

  • corn oil

  • soybean oil

  • grapeseed oil

  • sunflower seeds

  • walnuts

  • pumpkin seeds

Good sources of omega-3 fats include

  • oily fish such as salmon, tuna, sardines

  • flaxseeds

  • walnuts

  • chia seeds

Seed oils are in a lot of processed foods and contain saturated fat, added sugars, and sodium. Consume these foods less often.

It’s easy to add more omega-6 and omega-3 fats throughout your day.

  • For breakfast, add walnuts, pumpkin, and chia seeds to your favorite cereal or oatmeal.

  • For lunch, have a salad topped with a homemade salad dressing made with grapeseed oil and vinegar. Add sunflower seeds for crunch.

  • For dinner, prepare roasted salmon with quinoa and vegetables.

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