Seed oils have become one of the most controversial topics in nutrition. You may have heard that they cause inflammation, are overly processed, or should be avoided altogether.
But are seed oils actually unhealthy?
The short answer is: there’s no good reason for most people to fear seed oils. Like any source of dietary fat, they can be part of a balanced diet. And when we zoom out from individual ingredients and look at overall dietary patterns, the evidence does not support treating seed oils as uniquely harmful.
For dancers, this distinction matters. Food does not need to be perfect to be nourishing. If fear of a particular ingredient is making eating more stressful, restrictive, or complicated, that deserves our attention, too.
Let’s unpack what the research actually tells us about seed oils, inflammation, omega-6 fats, cooking, and heart health.
What are seed oils?
Seed oils are vegetable oils extracted from the seeds of plants. Seed oils can be produced using a variety of extraction and refining methods. Common examples include:
- Canola oil
- Soybean oil
- Corn oil
- Sunflower oil
- Safflower oil
- Grapeseed oil
- Flaxseed oil
- Sesame oil
- Peanut oil
Other plant-based cooking oils, such as olive, avocado, coconut, and palm oils, come from fruits or other parts of plants rather than seeds.
Refined oils undergo processing that can include heat, filtration, and other techniques used to remove impurities, color, and odors and create an oil with a neutral flavor and longer shelf life. Some extraction processes may use solvents such as hexane, which is subsequently removed from the finished oil. Refined oils are sometimes chemically altered to withstand high-heat cooking methods like frying.
Unrefined oils, including many cold-pressed oils, undergo less processing and generally retain more of the flavor, aroma, pigments, and naturally occurring compounds from the original plant. They’re also known to retain more of their antioxidative properties.
You’ll often see the words refined, bleached, and deodorized used as evidence that seed oils are somehow dangerous. But processing itself does not automatically make a food unhealthy.
In fact, food processing is incredibly broad. Washing, freezing, grinding, fermenting, pasteurizing, cooking, and refining are all forms of food processing. The important question is what processing does to the food and how that food fits into the overall diet.
Why are seed oils controversial?
The current backlash against seed oils is driven largely by claims that they are:
- Highly processed
- Toxic
- Inflammatory
- Unstable when heated
- Too high in omega-6 fatty acids
- Responsible for chronic disease
These claims can sound convincing when presented in isolation. But nutrition research rarely supports conclusions that simple.
One particularly common concern is the use of chemical solvents such as hexane during oil extraction. While the word “chemical” can certainly sound alarming, the presence of a chemical does not automatically make a food dangerous. Hexane is removed during processing, and any residual amounts in food are tightly regulated and present at very low concentrations. There is also no evidence to support any risk or danger from the consumption of foods containing trace residual concentrations of hexane
In other words, the fact that an ingredient was processed using a chemical does not tell us whether eating the finished food is harmful. And if worrying about trace ingredients is causing you to feel anxious about food, that is worth considering as part of the nutrition equation, too.
What types of fat are found in seed oils?
To understand seed oils, it helps to understand dietary fat. Dietary fats can be broadly categorized as:
- Saturated fats are found in foods such as butter, cheese, full-fat dairy, and many meats. Some plant foods, including coconut and palm oil, are also relatively high in saturated fat.
- Monounsaturated fats (MUFAs) are abundant in foods such as olive oil, avocado, nuts, and some seeds.
- Polyunsaturated fats (PUFAs) include both omega-3 and omega-6 fatty acids. They are found in foods such as nuts, seeds, fatty fish, and many plant-based oils.
- Trans fat is a product of food processing (but also found naturally in trace amounts of some foods). While trans fats have been associated with an increased risk of heart disease, they’ve also been removed from our food supply since 2018– so worrying about trace amounts, even those from partially hydrogenated oils, isn’t worth it.
Most cooking oils contain a combination of different fatty acids, but the proportions vary. This is why I don’t love the question, “What is the healthiest oil?” Nutrition is rarely that black and white. Instead, I encourage you to ask: What role does this food play in my overall eating pattern?
Are seed oils good for your heart?
This is where the research becomes particularly important. Replacing some sources of saturated fat with polyunsaturated fat is associated with improvements in blood cholesterol and a lower risk of cardiovascular disease. Many commonly criticized seed oils, including soybean, corn, sunflower, and canola oils, are rich in these unsaturated fats.
This doesn’t mean you need to replace every source of saturated fat in your diet with seed oils. It simply means that seed oils shouldn’t automatically be categorized as unhealthy because they’re “processed” or because they contain omega-6 fatty acids.
Seed oils also contain other beneficial compounds, including phytosterols and polyphenols, as well as vitamin E, a powerful antioxidant. A certain degree of oxidative stress is normal in the human body, but excessive oxidative stress has been associated with disease. Antioxidants, including vitamins E and C, help protect cells from oxidative damage.
So rather than asking, “What’s the healthiest oil?” I think it’s more useful to zoom out. The overall pattern of your diet matters far more than whether a single bottle of oil lives in your pantry.
Here’s an image that demonstrates the various concentrations of fats in different cooking oils. (Side note: this is a very old image from CSPI. Funny enough, it doesn’t even include avocado oil, likely because it wasn’t the trend it is today!)
Are omega-6 fats inflammatory?
This is probably the biggest nutrition myth surrounding seed oils. The argument usually goes something like this: Seed oils are high in omega-6 fats → omega-6 fats cause inflammation → seed oils cause inflammation. The problem? Current research does not support this chain of reasoning.
Linoleic acid is the primary omega-6 fatty acid found in many seed oils. Although omega-6 fatty acids can be converted into other compounds involved in inflammatory pathways, that biochemical fact does not mean that eating omega-6-rich foods causes chronic inflammation in humans.
Research examining dietary linoleic acid has not demonstrated that increasing intake causes an increase in inflammatory markers. In fact, replacing saturated fat with polyunsaturated fat, including omega-6 fats, can have cardiovascular benefits. Here’s another review of the literature that disputes the claim that polyunsaturated fat, particularly omega-6 linoleic acid, is pro-inflammatory.
The idea that we need to dramatically reduce omega-6 fats because they are inherently “pro-inflammatory” oversimplifies how fatty acid metabolism works.
What about the omega-6-to-omega-3 ratio?
You may also have heard that modern diets contain “too much omega-6 and not enough omega-3.” While omega-3 fats are certainly important, the idea that there is one ideal dietary omega-6-to-omega-3 ratio that everyone needs to achieve is not well supported by evidence.
Rather than obsessing over a ratio, focus on including a variety of fat sources, including omega-3-rich foods such as salmon, walnuts, chia seeds, flaxseed, and hemp seeds.
Again, zoom out. Here’s a fantastic article that dives deeper into the pseudoscience surrounding seed oils and associated polyunsaturated fats. Food Science Babe also debunks these fears, among others, at length.
Cooking oils
The key advantage of oils is their versatility in the kitchen— allowing us to incorporate them seamlessly into our daily meals, and enjoy their health benefits, without compromising the taste of our dishes. But there are speculations surrounding whether some oils are safer to cook with than others.
It is true that different oils react differently to heat. When overheated, oils break down, producing polar compounds that may be harmful to health. A 2018 study found that oils predominant in saturated fats (ie. butter, coconut oil) and monounsaturated fats (ie. extra virgin olive oil) are most heat stable, while those predominate in polyunsaturated fats (canola, vegetable, grapeseed) are less heat stable. This goes against popular opinion, which suggests that we should utilize an oil’s smoke point to determine whether or not it’s best for cooking. In fact, the researchers concluded that oils with the highest smoke points – canola, sunflower, and grapeseed – produced the highest levels of harmful compounds when overheated. Here’s a great article that speaks more on the topic.
With all this said, limitations of this study exist. First, the oils tested were heated alone and according to the authors, “…the absence of food… may have allowed for a greater impact of oil oxidation.” Another consideration is the presence of antioxidants (vitamin E is most potent in extra virgin olive oil). This potency might help to explain the lowered rate of oil degradation.
What’s the best oil to cook with?
Despite these newer findings, it’s important to consider the practicality of these results through a wider lens. First, are you burning your oil before cooking with it? Likely no. In fact, many home-cooking methods won’t reach temperatures that risk severe degradation of oil. If you are deep frying, avoid recycling your oil over time (those harmful compounds can build up). Last, patterns over time always matter, and variety is key when it comes to nutrition. A few considerations:
- For frying, choose an oil with a high smoke point (see below). Refined oils, avocado oil, safflower oil, and vegetable oil are examples. Don’t reuse the oil.
- For baking, aim for a neutral-tasting oil like avocado or vegetable oil as these won’t alter the flavor of your finished product.
- For sautéing or searing, try a flavorful oil (ie. extra-virgin olive oil or avocado oil)— these may produce the least amount of polar compounds when heated.
- For salads and dressings, extra virgin olive oil is a great option because it has a flavorful profile and contains a variety of beneficial plant compounds.
So, are seed oils unhealthy?
No, seed oils do not need to be avoided as a category. Current evidence does not support the idea that seed oils are uniquely inflammatory or toxic. Many seed oils provide unsaturated fats, and replacing some saturated fat with polyunsaturated fat can support cardiovascular health.
That doesn’t mean every food containing seed oils is automatically nutritious. A packaged cookie, for example, isn’t transformed into a health food because it contains canola oil.
But the reverse is also true: the presence of a seed oil does not make a food unhealthy. This distinction is incredibly important. If a food contains an ingredient you have been told to fear, ask yourself: What does the entire food look like? What does my overall diet look like? And is avoiding this ingredient actually improving my health, or is it simply making eating more stressful?
The bottom line
You do not need to choose the “perfect” cooking oil. You can use extra-virgin olive oil for your salad, canola oil for your muffins, avocado oil for sautéing, coconut oil when you enjoy its flavor, and yes, even butter when that’s what makes your meal satisfying.
Nutrition is not about finding one perfect ingredient or eliminating every potentially controversial one. The goal is to build an eating pattern that is nourishing, satisfying, flexible, and sustainable.
For dancers especially, I would much rather see you comfortably enjoy a meal cooked with a seed oil than spend your mental energy worrying that a teaspoon of canola oil is somehow harming your body. Your health is shaped by your overall pattern of eating, not by one ingredient in one meal. And sometimes, the healthiest choice is the one that lets you eat without fear.
