If you’ve spent any time online in the last couple years, you’ve likely come across heated conversations about seed oils. Seed oils are often criticized by skeptics, linking them to chronic inflammation, and diseases like heart disease, obesity, and diabetes.
Fortunately, science tells a much different story.
What Are Seed Oils?
Seed oils are vegetable oils extracted from the seeds of plants. Common examples include canola, sunflower, soybean, corn, grapeseed, and safflower oils.
These oils are valued for several reasons—they’re affordable, neutral in taste, have a high smoke point that makes them ideal for cooking and are high in polyunsaturated fats (particularly omega-6 fatty acids). Omega 6 fatty acids act to lower LDL cholesterol, thereby helping prevent cardiovascular disease. Similar to DHA, arachidonic acid (derived from omega 6) also contributes to a healthy brain.
Opponents argue that because seed oils are used in many processed foods, they’re inherently unhealthy. But it’s important to separate seed oils themselves from the highly processed foods they’re often found in—products like chips, frozen dinners/desserts, granola/sports bars, fast-food fries, etc. The real concern should be monitoring ultra-processed foods in your diet, which are hyperpalatable and very easy to overeat. They often contain unhealthy additives, refined carbohydrates, added sugar, and sodium, which are all things we know in excess can impact our health negatively.
There are many beliefs about seed oils that continue to spark debate, and not all of them are rooted in scientific evidence. To understand this topic, it’s important to address common myths about seed oils, and explore the facts behind them.
Myth #1: Seed Oils Create Chronic Inflammation
This belief stems from the idea that omega-6 fatty acids in seed oils promote inflammation in the body. While it’s true that omega-6 fatty acids are precursors to certain inflammatory compounds, the relationship is far more nuanced. Research consistently shows that omega-6 fats are an essential part of a healthy diet and can even reduce the risk of chronic diseases like heart disease.
The Evidence:
- Research shows that linoleic acid, the predominant omega-6 fatty acid in seed oils, lowers LDL cholesterol and is linked to a decreased risk of type-2 diabetes, coronary heart disease, and stroke.
- Another large-scale meta-analysis in Circulation pooled data from 30 cohort studies and found that higher circulating levels of linoleic acid were associated with a 22% reduced risk of cardiovascular mortality and a 12% lower risk for ischemic stroke.
Myth #2: Heating Seed Oils Makes Them Toxic
When you heat seed oils, they can break down and produce substances that may damage your cells. This is more likely to happen with oils that have been refined using high heat. To minimize this risk, it’s important not to heat oils past their smoke point and avoid reusing them repeatedly. Although you can’t completely prevent this breakdown because it’s a natural process, you can reduce it by cooking at lower temperatures and storing oils and foods that contain fats properly.
The Evidence:
Oils rich in PUFAs, such as sunflower oil, do undergo oxidation when heated; however, the extent of oxidation is relatively minor compared to the overall dietary intake of antioxidants. Research indicates that cooking with fresh oil at moderate temperatures, like during stir-frying, does not result in significant oxidation or pose notable health risks. It is therefore important to note the smoke point for the oil you wish to use and try not to exceed that temperature.
Myth #3: Processing Strips Away All Nutritional Value
Seed oils undergo processing—whether that’s cold-pressed, expeller-pressed, or chemically refined. Critics often argue that refined oils are “toxic” or “empty-calorie” products void of nutrition.
Refining seed oils doesn’t render them unhealthy. Most of their nutritional composition remains intact. The real question we should be asking is this—do these oils contain essential fatty acids and do they contribute to better health outcomes? Overwhelmingly, the answer is yes.
The Evidence:
Through decades of studies, consuming oils rich in linoleic acid in healthy amounts have been linked to lower LDL cholesterol, improved insulin sensitivity, and reduced central obesity—all winners for anyone concerned about chronic disease prevention.
Reframing the Omega-6 Story
The wellness industry often portrays omega-6 fats as harmful compared to omega-3 fats, leading some to believe they should be avoided entirely. While it’s true that many modern diets contain too much omega-6 relative to omega-3, the goal should be balance, not elimination.
To ensure health-promoting levels of omega-3 fatty acids, most individuals should obtain more EPA and DHA from sources such as oily fish or algae (for those who are plant-based). Sufficient levels of both EPA and DHA are integral to brain health. These sources are preferable to ALA (found in plant-foods like flaxseed, walnuts, and chia seeds), which convert inefficiently to EPA and even less so to DHA.
What Seed Oil Critics Get Right
There is one area where seed oil critics often make a valid point. Many ultra-processed foods rely on seed oils for shelf stability and taste. These processed items are also high in sodium, sugar, or refined carbohydrates—nutritional factors that can contribute to inflammation and poor health. Blaming seed oils for these problems overlooks the bigger picture.
A Healthier Perspective on Fats
When it comes to dietary fats, variety and moderation are key. A simple, actionable guideline for improving fatty acid balance is to focus less on cutting out omega-6 fats and more on prioritizing omega-3 fatty acids, monounsaturated fats, and reducing saturated fats.
General Guidelines to optimize healthy oils and fats in your diet:
- Use extra virgin olive oil most often for salad dressings, dips, and low to moderate heat cooking.
- Use avocado oil which has an excellent nutrient/health profile for higher heat cooking and baking as it has a higher smoke point (~500 degrees Fahrenheit).
- Aim for a minimum of 2 servings of oily fish (ex. salmon, trout, arctic char, sardines, mackerel, sablefish, etc) per week to obtain adequate amounts of essential omega-3 fats, including EPA & DHA.
- If you are plant-based or don’t eat oily fish regularly, then speak to your dietitian about supplementing your diet with good quality fish or algae oil
- Use seed oils in moderation, to complement recipes and cooking methods with the smoke point factored into your usage. For example:
- Sesame oil has a strong taste and is perfect for dressings and marinades
- Canola oil has a neutral flavour, high smoke point, and is an excellent choice for baking and even grilling
- Include whole nuts, seeds and avocado in your diet regularly.
- Reduce saturated fats which come from foods like red meat, processed meats, chocolate, high fat dairy like cheese, butter and coconut oil. Saturated fats are a prominent driver of LDL (lousy) cholesterol, are associated with an increased risk of cardiovascular disease, and are linked to increased inflammation, and cognitive decline.
- Any oil is calorie dense – 120 Kcal per tablespoon – so watch how much you spread on your pan when cooking stir fries or making salad dressing.
Striking a Balance
The evidence is clear—when seed oils are consumed as part of a diverse diet, they can contribute to better heart and metabolic health outcomes. Rather than letting wellness trends dictate your diet, focus on balancing your overall nutrient intake, eating whole foods, and minimizing ultra-processed products. As always, working with your dietitian to tailor your diet and meal planning to your specific needs can help you use and consume seed oils in a healthy way.
