Karen Collins
Key Takeaways:
- Current research does not support social media claims that seed oils cause inflammation or major diseases.
- The omega-6 fats in seed oils are helpful, not harmful, as part of a healthy diet.
- Oil processing methods are being studied, but there’s no strong evidence linking health risks from eating seed oils.
Have you seen warnings on social media calling seed oils “toxic”? Don’t believe the hype. Oils like canola, corn and soybean are in the spotlight, and this blog will help you understand why they have become one of the most controversial topics in nutrition.
Many social media influencers warn that seed oils cause inflammation and chronic disease. But these claims oversimplify science and overlook decades of research that highlights the benefits of oils.
Let’s take a closer look at what seed oils are, where the concerns come from and what the evidence shows about their effects on health.
What Are Seed Oils?
“Seed oils” are vegetable oils produced from seeds. You won’t see “seed oil” listed on food labels—each oil has its own name. Some common seed oils are:
- Canola oil
- Corn oil
- Cottonseed oil
- Grapeseed oil
- Rice bran oil
- Safflower oil
- Soybean oil
- Sunflower seed oil
Although all seed oils are vegetable oils, not all vegetable oils come from seeds. For example:
- Olive, avocado and coconut oils come from the flesh of fruits
- Almond and walnut oil come from nuts
What Is the Concern about Seed Oils?
Some online posts warn against eight specific seed oils (listed above), calling them the “hateful eight.” The two big concerns are:
- Omega-6 fats: claimed to be “unstable” and cause inflammation
- Chemical processing: claimed to leave toxic residue from hexane
Let’s take a closer look at each of these topics in more detail and separate myth from fact.
Seed Oils, Omega-6 Fats and Inflammation
Inflammation plays both protective and potentially harmful roles in health. Inflammation can serve a critical purpose: It helps fight infections and heal damaged tissues. But when inflammation becomes chronic low-grade inflammation in the body, it can contribute to serious health concerns.
Over time, inflammation in certain body parts can increase the risk of cancer, heart disease and type 2 diabetes.
Claims that seed oils could promote inflammation come from early studies on how different types of fat are broken down. Many seed oils are high in polyunsaturated fat, especially a particular omega-6 fat called linoleic acid. Linoleic acid can be converted into arachidonic acid, which can produce some pro-inflammatory signaling molecules. But those early findings were lab-based, and not reflective of whole human diets.
Yet, social media influencers rely on these outdated lab studies to create fear-mongering content, while ignoring large-scale human studies that show seed oils are fine. It’s misleading and cherry-picked science, but it’s not the whole story.
The truth? More recent studies show:
- The body converts only a tiny fraction of omega-6 into compounds that can promote inflammation.
- Omega-6 fats also help make anti-inflammatory compounds.
- Diets higher in omega-6 fats are not associated with biomarkers of chronic inflammation.
- There is often lower chronic inflammation when diets are higher in omega-6 fats.
- Higher omega-6 levels are associated with lower risk of death from all causes, cardiovascular disease and cancer.
Seed Oils and Chemical Processing
Hexane is a solvent used to pull oil from crushed seeds. This method is efficient and recovers more oil from seeds than relying on mechanical pressing alone. Afterward, the hexane is evaporated out, and the oil is refined further to create a stable product with neutral flavor and a long shelf life.
While the FDA does not monitor hexane content in seed oil, the industry standard is to remove the solvent, leaving behind trace amounts (less than 1 part per million). Since the FDA does not regulate hexane residue in cooking oils, it’s unclear what trace amounts of hexane remain in seed oils. For comparison, the European Union set a maximum residual limit of 1 mg/kg of hexane residue in vegetable oils.
But remember that hexane is found in many places. Most exposure to hexane comes from breathing air contaminated with it, such as from solvents in the workplace, cleaning products in the home or gasoline fumes. Current evidence does not establish whether there are health risks related to these trace levels. Several U.S. and European reports concluded that hexane does not appear to cause DNA damage that could lead to cancer.
Studies have found traces of hexane in the urine of the general population. This shows that low-level exposure is common, even among people who are not exposed to hexane at work. Evidence does not show that seed oil consumption is necessarily the source of this exposure.
Should I Switch to Butter or Beef Tallow?
Animal fats like butter, lard and beef tallow are popular with some social media influencers. But what does research show about animal fats and other oils as replacements for seed oils?
Butter, tallow (rendered beef fat) and lard (rendered pork fat) are high in saturated fat. Research shows that diets high in saturated fat raise blood levels of bad LDL-cholesterol, which increases risk of heart disease. Replacing foods high in saturated fat with unsaturated fats helps lower these levels.
Despite what some social media influencers say, beef tallow and lard are not a source of fat-soluble vitamins. They contain no vitamin A or vitamin K, and only a trace of vitamin E and vitamin D.
Practical tip: Choosing buttery toast, French fries cooked in tallow or pie crust made with lard once in a while won’t undo an overall healthy diet. But choosing any of these fats for everyday use does not line up with overall research. Instead, studies show that replacing foods high in saturated fat (like butter or lard) with unsaturated fats from oil is better for heart health.
What about Other Oils?
Other oils come from fruits and nuts. Here are some other healthy oil options:
- Olive oil is high in monounsaturated fat. Extra virgin olive oil contains polyphenols and other compounds that may help support body antioxidant defenses and promote healthy blood vessel function.
- Avocado oil is mainly monounsaturated fat, too. Refined types have a high smoke point, making it good for high-heat cooking. Extra virgin (unrefined) avocado oil has a lower smoke point. Choose the right one depending on what you will use it for (for example, high heat cooking versus making salad dressing).
- Nut oils include almond, walnut and others. Many are higher in polyunsaturated fat and have a low smoke point, making them excellent for flavor on salads or after cooking. Nut oils may be produced by pressing or with solvent extraction.
Practical tip: Choose oils that contain mainly unsaturated (polyunsaturated or monounsaturated fat) based on your cooking style, flavor preferences and budget. This allows you to enjoy delicious food and keep a healthy diet without being distracted by unfounded food fears.
