Have you heard the claim that seed oils are “toxic”? Some social media users blame them for everything, from acne and weight gain to cancer and infertility. But as is so often the case, the truth is a lot more nuanced than TikTok typically reveals.
Registered dietitian Julia Zumpano, RD, LD, explains what seed oils are, what they can do to your body, and whether you need to cut them out entirely or just try to focus on a healthy, balanced diet. (Hint: It’s the latter.)
What Are Seed Oils?
Seed oils first emerged in the late 1900s as an alternative to partially hydrogenated oils. They’re plant-based cooking oils made from — you guessed it — the seeds of various plants.
These seeds are turned into oils that have become extremely common in both cooking and baking.
- Home cooking. You might put a few tablespoons of canola oil in a healthy muffin recipe or use it to pan-fry potato pancakes.
- Fried foods. These oils are also frequently used in restaurants and fast-food spots, where canola oil is the oil of choice for deep-frying.
- Processed and ultra-processed foods. Seed oils can be found in all kinds of packaged foods, including some frozen foods and even chocolate. They’re also sometimes added to foods marketed as “healthy,” including whole-grain crackers and breads, protein shakes, dressings and sauces.
But seeds themselves can be a really healthy addition to your diet. So, shouldn’t the same be true of oil made from seeds? Not quite.
“Seed oils are made through a chemical process where they’re bleached, refined and heated in order to be usable,” Zumpano explains. That process strips the seeds of their nutrients.”
Types of Seed Oils
Seed oils commonly used today include canola, corn, cottonseed, soybean, sunflower, safflower, grapeseed, rice bran, and peanut oil. Collectively, they are sometimes criticized as being unhealthy and are often referred to negatively in discussions about modern diets. Yet the question remains: are they truly harmful on their own, or is it the way they are incorporated into food that makes them a concern?
Potential Health Concerns
Seed oils are often criticized for being highly refined and chemically processed. The refining process can involve multiple steps such as bleaching and deodorizing, which strip away beneficial compounds like vitamin E and natural antioxidants. This results in oils that provide calories but few nutrients. While this is a common issue in many refined oils, seed oils have gained particular attention due to their widespread use in processed foods.
Another concern is that seed oils are frequently found in foods that are already unhealthy, such as fried meals, fast food, and packaged snacks. Consuming them in these contexts often means consuming large amounts of added sugar, sodium, and unhealthy fats alongside the oils. Research has shown that diets high in ultra-processed foods are associated with an increased risk of metabolic issues and poor overall health, making the context of consumption just as important as the oils themselves.
The Role of Omega-6 Fats
Seed oils are naturally high in omega-6 fatty acids, particularly linoleic acid. While the body does require some omega-6s for essential functions, problems arise when the balance between omega-6 and omega-3 fatty acids becomes distorted. In an ideal diet, the ratio of omega-6 to omega-3 fats should be close to equal. However, modern diets often lean heavily toward omega-6, sometimes at ratios as high as 20:1. This imbalance is thought to contribute to chronic inflammation, which has been linked to conditions such as heart disease, diabetes, arthritis, and stroke.
Should You Avoid Seed Oils?
Occasional use of seed oils in cooking is unlikely to cause harm, but issues arise when they are consumed in large quantities, particularly through highly processed foods. Heating seed oils to very high temperatures or reusing them can worsen their effects, so it is best to avoid these practices at home. Some people choose to eliminate seed oils altogether, and while doing so is not harmful, the greater benefit often comes from reducing overall processed food intake.
Alternatives and Better Choices
Healthier oils such as extra-virgin olive oil or avocado oil are often recommended for home cooking. They are less refined, higher in beneficial monounsaturated fats, and retain more of their natural nutrients. These alternatives can be used safely in a variety of cooking methods and provide additional health benefits. That said, if seed oils are used occasionally at home in moderation, they are not nearly as concerning as when consumed through fast food and ultra-processed meals.
Conclusion
Seed oils themselves are not inherently toxic, but the way they are produced and consumed has raised important health questions. The biggest issue is not necessarily the oils on their own but their frequent presence in heavily processed and fast foods, which are already linked to poor health outcomes. When consumed in moderation and balanced with nutrient-dense whole foods, seed oils are less likely to cause harm.
Ultimately, the focus should be on maintaining a balanced diet rich in whole, unprocessed foods while keeping overall oil consumption moderate. By prioritizing healthier cooking oils at home and reducing reliance on processed meals, you can support a healthier balance of fats and lower your risk of chronic inflammation. The real key lies not in demonizing seed oils but in cultivating dietary habits that promote long-term well-being.
