Seed oils are cooking oils extracted from the seeds of plants, and the term has become shorthand in health circles for a specific group of highly refined, industrially processed vegetable oils. The most commonly cited seed oils include soybean oil, canola oil (also called rapeseed oil), corn oil, sunflower oil, safflower oil, cottonseed oil, grapeseed oil, and rice bran oil. These oils are distinct from oils pressed from the flesh of a fruit, like olive oil or avocado oil, and from animal fats like butter or lard.
The Full List of Seed Oils
While the term technically applies to any oil derived from a seed, the oils that typically come up in the “seed oil” conversation are the ones produced at industrial scale and used widely in processed food and restaurant cooking. Here’s the list:
- Soybean oil: The most consumed oil in the United States, often simply labeled “vegetable oil” on bottles and ingredient lists.
- Canola oil (rapeseed oil): Widely used for frying, baking, and salad dressings due to its neutral flavor.
- Corn oil: Common in snack foods and deep frying, especially in Hispanic cuisine for items like tortilla chips.
- Sunflower oil: Found in chips, crackers, sauces, mayonnaise, and used in restaurant fryers.
- Safflower oil: Similar to sunflower oil in use, often found in processed foods and margarine.
- Cottonseed oil: Popular in chip production and commercial baking, historically one of the first industrial seed oils.
- Grapeseed oil: Marketed as a higher-end cooking oil, extracted from the seeds left over from winemaking.
- Rice bran oil: Common in Asian cooking and increasingly used in snack food manufacturing.
Other oils that technically come from seeds, like peanut oil, pumpkin seed oil, and chia seed oil, tend to get less scrutiny in the seed oil debate. Peanut oil, for instance, is widely used in restaurant deep fryers but is often grouped separately because of its longer culinary history and different fatty acid profile.
How Seed Oils Are Made
What sets these oils apart from something like extra virgin olive oil isn’t just the source plant. It’s how they’re processed. Most commercial seed oils go through a multi-step industrial refining process that looks nothing like simply pressing oil from a seed.
The standard method is solvent extraction using hexane, a chemical listed as a hazardous air pollutant under the 1990 Clean Air Act. Seeds are crushed, then washed with hexane to dissolve and pull out the oil. The hexane is later removed through distillation columns and steam stripping, but the process is far more chemical-intensive than mechanical pressing. After extraction, the crude oil goes through refining steps to remove impurities, followed by bleaching to lighten the color and deodorizing to strip out any off-flavors or smells.
Some seed oils are produced using mechanical screw presses, where increasing pressure physically squeezes oil out of the seeds. Cold-pressed or expeller-pressed versions of sunflower or safflower oil exist, but they represent a tiny fraction of the market. The vast majority of seed oil on grocery shelves and in restaurant kitchens is solvent-extracted and fully refined.
Why Omega-6 Content Matters
The main nutritional concern around seed oils centers on linoleic acid, an omega-6 polyunsaturated fatty acid. Your body needs some omega-6 fats, but the quantity in the modern diet has increased dramatically as seed oil consumption has risen. Conventional soybean oil, for example, is 54% linoleic acid. That’s significant when you consider soybean oil is the most widely used cooking oil in the country and appears in everything from salad dressings to fast food fryers to packaged snacks.
Not all seed oils have identical profiles. Sunflower oil comes in several varieties: conventional versions are high in linoleic acid, while “high oleic” sunflower oil contains only about 6% linoleic acid and is much closer in composition to olive oil. Mid-oleic sunflower oil (sometimes labeled NuSun) falls in between at roughly 29% linoleic acid. High oleic soybean oil drops to around 1% linoleic acid. These newer cultivars were specifically bred to reduce the omega-6 content, so the type of seed oil matters, not just whether something is a seed oil at all.
Where You’ll Encounter Them
Seed oils are nearly impossible to avoid if you eat out or buy packaged food. Restaurants overwhelmingly rely on canola oil, soybean oil, and sunflower oil for deep frying because they’re cheap, have neutral flavors, and tolerate high heat. Bottles labeled “vegetable oil” in grocery stores are typically 100% soybean oil. Clear frying oils used in commercial kitchens are also soybean-based, with smoke points around 450°F.
Beyond the fryer, seed oils show up in mayonnaise, salad dressings, crackers, chips, cookies, bread, frozen meals, protein bars, and most other processed foods. Reading ingredient labels is the only reliable way to know which oil is in a product. If a label says “vegetable oil” without further detail, it’s almost certainly soybean oil.
What Health Authorities Say
Official guidelines and online health communities don’t agree on seed oils. The American Heart Association recommends replacing saturated fats (like butter, lard, and coconut oil) with polyunsaturated and monounsaturated fats, and specifically lists canola, corn, soybean, sunflower, safflower, and peanut oils as healthier choices. Their guidance is to choose oils with less than 4 grams of saturated fat per tablespoon and to avoid partially hydrogenated oils containing trans fats.
Critics of seed oils argue that this advice doesn’t account for the dramatic increase in omega-6 consumption over the past century, the oxidation potential of polyunsaturated fats when repeatedly heated, or the effects of industrial processing. The European Food Information Council notes that the risk of oxidation increases when oils are exposed to heat, light, and air for prolonged periods, and recommends using seed oils within their smoke points and avoiding overheating to limit the formation of harmful byproducts.
The practical reality is that seed oils are the dominant fat in the modern food supply. Whether you choose to reduce them or not, knowing which oils fall into this category and where they hide in your diet gives you the information to make that decision for yourself.