Seed Oils: What They Are, the Full List, and What the Evidence Says

Seed oils are cooking oils extracted from the seeds of plants. The eight most often named are canola, soybean, corn, cottonseed, sunflower, safflower, grapeseed and rice bran. Most are heavily refined and rich in omega-6 linoleic acid. Whether they harm health is genuinely debated: large studies link them to lower heart risk, while critics point to processing and older trials.

If you have started reading labels and noticed soybean or canola oil in nearly everything, you are not imagining it. That observation is fair, and it is where a lot of people start asking questions. This guide lays out the list, how the oils are made, the strongest version of the case against them, and what the research shows, so you can decide for yourself.

What are seed oils?

“Seed oil” is a popular term rather than a scientific category. It usually means a vegetable oil that comes from an oilseed crop and is produced at industrial scale, as opposed to oils pressed from fruit (olive, avocado, coconut) or fats rendered from animals (butter, tallow, lard).

Two of the usual suspects are technically a stretch. Corn oil comes from the germ of the corn kernel, and rice bran oil comes from the bran layer of rice, so some writers note they are not true seed oils. They are grouped in because they are made and used in the same way.

The seed oils list

The list most people search for comes from physician Cate Shanahan, a central figure in the seed oil movement, who calls these the “hateful eight”:

1. Canola oil (rapeseed oil bred for low erucic acid)
2. Soybean oil (often labeled simply “vegetable oil”)
3. Corn oil
4. Cottonseed oil
5. Sunflower oil
6. Safflower oil
7. Grapeseed oil
8. Rice bran oil

Two practical notes. First, “vegetable oil” on a label is very often soybean oil or a blend. Second, sunflower and safflower oil come in “high-oleic” versions bred to be mostly monounsaturated fat rather than omega-6. They are still seed oils by the usual definition, but their fat profile is closer to olive oil.

Non-seed oils and fats

If you want to avoid seed oils, these are the common alternatives:

• Fruit oils: extra virgin olive oil, avocado oil, coconut oil, palm oil
• Animal fats: butter, ghee, beef tallow, lard, duck fat

Note that “not a seed oil” does not automatically mean “less processed.” Olive pomace oil, for example, is extracted from leftover olive pulp with solvents, and much coconut and avocado oil is refined.

How seed oils are made

This is where many people’s concern begins, and it is a fair place to start. Here is how a typical commercial plant works, according to a Penn State fact sheet on edible oil processing:

1. Clean and crush. Seeds are cleaned, sometimes hulled, broken into pieces and conditioned with heat.
2. Expeller press. A screw press squeezes out the first oil, leaving a compressed “press cake.”
3. Solvent extraction. The press cake is flaked and mixed with hexane, a petroleum-derived solvent, which dissolves the remaining oil. The hexane is then evaporated and distilled off for reuse. Combining pressing and solvent extraction leaves less than 1% of the oil in the leftover meal, which is mostly sold as animal feed.
4. Refine, bleach, deodorize (RBD). The crude oil is refined (gums and free fatty acids removed), “bleached” by filtering through clay (no household bleach is involved), and deodorized with steam, which strips out flavor and smell.

The result is an oil that is “generally tasteless, odorless, and colorless regardless of the original oilseed,” in the fact sheet’s words. RBD processing also removes some of the oil’s natural antioxidants, which is why antioxidants are often added back.

Expeller-pressed and cold-pressed oils skip the solvent. Small-scale expeller pressing leaves more oil behind in the meal, roughly 8–15% according to the same fact sheet, which is part of why these oils cost more. “Cold-pressed” means the oil was pressed below about 49 °C (120 °F). Unrefined pressed oils keep more of their original flavor and color.

Why do people say seed oils are bad?

Here is the case critics make, stated as fairly as we can:

• They are new to the human diet. US consumption of soybean oil rose more than 1,000-fold between 1909 and 1999, by one NIH-led estimate. Over the same period linoleic acid availability rose from about 2.8% to 7.2% of energy.
• Omega-6 balance. The same analysis estimated that the ratio of omega-6 linoleic acid to omega-3 ALA rose from 6.4 to 10.0, and its authors argued that rising linoleic acid likely lowered tissue levels of the omega-3s EPA and DHA.
• Industrial processing. High heat, solvents and deodorizing are a long way from pressing olives.
• Oxidation. Polyunsaturated fats are less stable than saturated fats. When oil is heated hard and reused, as in commercial deep fryers, it breaks down into oxidation products.
• Recovered trials. Researchers re-analyzed unpublished data from older trials that swapped saturated fat for oils high in linoleic acid. In the Minnesota Coronary Experiment, the corn-oil diet lowered cholesterol but showed no mortality benefit, and a meta-analysis of similar trials found no benefit on coronary deaths.
• Who funds what. Some influential studies on the other side declare industry funding, which understandably makes readers wary.

Several of these points come from serious researchers in peer-reviewed journals, not just social media. That is why the debate has not gone away.

What does the evidence actually show?

The strongest evidence on the other side is also substantial:

• Large observational studies. A 2019 analysis pooled 30 prospective studies from 13 countries, with 68,659 participants. Instead of relying on food questionnaires, it measured linoleic acid in blood and fat tissue. Higher levels were associated with lower risk of cardiovascular disease, cardiovascular death and stroke.
• The American Heart Association’s review. Its 2009 science advisory concluded that getting at least 5–10% of energy from omega-6 fats reduces coronary heart disease risk relative to lower intakes, and advised against cutting them.
• Saturated fat trials. A 2020 Cochrane review of 15 randomized trials (about 59,000 participants) found that cutting saturated fat reduced combined cardiovascular events by 21%. It found little or no effect on overall deaths or cardiovascular deaths. Swapping in polyunsaturated fat or carbohydrate did not make a significant difference.
• Current US guidance. The 2025–2030 Dietary Guidelines keep the limit of 10% of daily calories from saturated fat. They list olive oil, butter and beef tallow as cooking options and do not single out seed oils. Harvard’s nutrition department notes that soybean and canola oil are rich sources of essential fatty acids shown to lower LDL cholesterol.

The point both sides can agree on

Much of the seed oil people eat does not come from a bottle in their own kitchen. It comes in fried fast food, chips, crackers, cookies, frozen meals and restaurant cooking, the foods the NOVA system calls ultra-processed. Those foods are linked to poorer health in large studies regardless of which fat is in them.

So if you cut back on fried and packaged food and cook more at home, you will eat far less seed oil and far less ultra-processed food at the same time. Seed oil skeptics and mainstream nutrition researchers can both support that change, which makes it the most useful step to take first.

Cooking fats compared

Smoke point (the temperature at which a fat starts to smoke) varies a lot with how refined a product is. Published figures for the same oil often disagree. We have not listed numbers we could not source reliably. The rule of thumb is that refined oils tolerate higher heat than unrefined versions of the same oil.

What should you cook with?

There is no single “correct” fat, and the best choice depends on what you are cooking and what else you eat. A practical approach:

1. Make extra virgin olive oil your everyday oil. It is mechanically pressed, unrefined, and has a long track record in research on Mediterranean-style diets. Use it for sautéing, roasting and dressings.
2. Use animal fats for flavor, in proportion. Butter in baking, tallow for roast potatoes, lard in pastry. These are traditional whole-food fats. They are also high in saturated fat, so if your doctor is watching your LDL cholesterol, keep them to a supporting role. If you want to make your own, see how to render beef tallow.
3. If you buy a seed oil, choose the form you want. Expeller-pressed or cold-pressed avoids hexane. High-oleic versions are more heat-stable.
4. Do not reuse frying oil over and over, and do not heat any fat until it smokes heavily. Stop and start again with fresh fat.
5. Cut the fryer and the snack aisle first. This is where most of the seed oil, and most of the ultra-processed food, comes from.
6. Get omega-3s from food. If omega-6 balance worries you, eating oily fish such as salmon or sardines is a more direct fix than avoiding every seed oil.

How to spot seed oils on a label

Seed oils appear under many names: “vegetable oil,” “soybean oil,” “canola oil,” “corn oil,” “sunflower oil,” “safflower oil,” “cottonseed oil,” “may contain one or more of the following,” and “partially hydrogenated” or “interesterified” oils. Finding them on a label is often a sign that the product is ultra-processed. The same habit of reading labels will also help you spot synthetic dyes like Red 40.

The bottom line

The concern about seed oils is understandable. They entered the food supply fast, they are made in an industrial way, and some old trial data were buried for decades. But the best current evidence does not show that seed oils used in ordinary home cooking are a hidden poison, and some of it suggests the opposite. The change with the strongest support is cooking more of your own food from whole ingredients. If you do that, how much seed oil you eat takes care of itself.