What’s really in your cooking oil, and why it matters more than you think

The fat we got wrong (and how to make better choices)

For decades, fat was cast as the villain of our diets. Low-fat products flooded supermarket shelves, and oils that seemed light and neutral, vegetable oil, canola oil, sunflower oil, were promoted as the healthy choice. Many of us grew up with them in our kitchens without ever questioning whether they truly deserved that reputation.

Here’s the good news: modern nutritional science tells a much happier story. Good fats are not the enemy. They are actually among the most essential nutrients we need, for hormone production, brain development, cellular repair, and managing inflammation. The real problem was never fat itself. It is consuming the wrong kinds of fat, or cooking with the right fats in the wrong way.

What are seed oils?

Seed oils, also called vegetable oils or plant-based oils, are extracted from the seeds of plants. The most widely consumed include canola, corn, cottonseed, soybean, sunflower, safflower, grapeseed, and rice bran oils.

What most people do not realize is how these oils are made. Rather than being simply pressed from their source, they are typically produced through a heavy industrial process involving high heat, high pressure, and chemical solvents, including hexane, a compound derived from petroleum. The result is a highly refined product that bears little resemblance to anything found in nature.

These oils are popular with food manufacturers for practical reasons: they are cheap to produce, have a long shelf life, and have a neutral flavor. But the same refining process that makes them so convenient can also degrade the oil itself, causing oxidation and the formation of compounds that contribute to inflammation on a cellular level.

Omega-6, oxidation, and the importance of context

There seems to be a war on omega-6, with these fats often simply labeled “pro-inflammatory.” But as always, there is more nuance behind the label, and it’s worth taking a closer look.

The first important distinction is this: omega-6 itself is not the problem.

A lot of this reputation comes down to guilt by association. Omega-6 happens to be the dominant fatty acid in most seed oils, and seed oils happen to be the ones most often heavily processed, refined with heat, pressure, and solvents, then used and reused in fried and ultra-processed foods. So omega-6 quietly absorbed the blame for what was really a processing problem. The same fatty acid, found fresh and unprocessed in whole foods like nuts, seeds, and their naturally pressed oils, does not carry the same baggage. The issue was never really the fat itself. It was the industrial journey it was so often forced through before it reached our plates.

The essential fatty acids: omega-6 and omega-3

Omega-6 and omega-3 are families of polyunsaturated fatty acids, and our bodies need both.

The two essential fatty acids are linoleic acid (LA), an omega-6, and alpha-linolenic acid (ALA), an omega-3. They are called essential because our bodies cannot make them, so we must get them through food. Together, they contribute to cell-membrane structure, cellular signaling, and the regulation of inflammatory processes.

The omega-6 family begins with LA, which can be metabolized into compounds including GLA, DGLA, and arachidonic acid (AA). The omega-3 family begins with ALA, which can be converted, although relatively inefficiently, into EPA and DHA.

Rather than thinking of it as omega-6 equals bad and inflammatory, and omega-3 equals good and anti-inflammatory, it is far more accurate, and far more useful, to see them as two interconnected families of essential fats, each playing its own role in human physiology.

Processing and quality matter

Many commonly consumed seed oils undergo industrial processing that may include extraction, refining, bleaching, deodorization, heat, and, in some cases, solvents. That is why quality, freshness, storage, and how an oil is used all matter so much.

A fresh, appropriately produced, and properly stored source of omega-6 should never simply be equated with an oil that has undergone substantial oxidative degradation. They are, in effect, two very different products.

What about the omega-6 to omega-3 ratio?

You will often see proposed ratios such as 3:1 or 4:1, but the truth is the ideal ratio is still debated. The absolute amounts, the individual fatty acids involved, food sources, and the overall diet all matter just as much.

Our fatty-acid status is shaped by diet, metabolism, absorption, genetics, and other individual factors. This is exactly why it helps to look at a broader fatty-acid profile, such as one from Nordic Laboratories, and see the actual data rather than assume one ratio is optimal for everyone. Seeing your own data is always the way forward, rather than guessing or taking supplements blindly. Testing genuinely matters here.

The bigger picture

Seed oils are now widespread in fried foods, restaurant foods, and ultra-processed products, where their processing, storage, and repeated exposure to heat can vary enormously.

So instead of declaring war on omega-6, perhaps the better move is to ask better questions: Where did the fat come from? How was it produced and stored? Is it fresh? Has it been exposed to excessive or repeated heat? Are we getting enough omega-3? And what does the rest of our diet actually look like? And… start eating home cooked meals where you can control what goes into your body.

Why heat makes things worse

There is another layer to this story, and it involves what happens to these oils once you start cooking with them.

Seed oils are polyunsaturated fats (PUFAs), which means they are chemically unstable. When exposed to heat, especially the high temperatures used for frying or roasting, they break down into a range of harmful compounds, including aldehydes, lipid peroxides, and other oxidized byproducts. These substances can damage cells and contribute to oxidative stress in the body.

The key factor here is a concept called the smoke point, the temperature at which an oil begins to break down. But smoke point alone does not tell the whole story. What matters just as much is the fat’s chemical structure. Saturated and monounsaturated fats are far more stable under heat than polyunsaturated fats, which is exactly why oils like coconut oil, ghee, and avocado oil are considerably safer choices for high-heat cooking.

Another important variable is how the oil was extracted and refined. Oils that are mechanically pressed, labeled as expeller-pressed or cold-pressed, are superior to those extracted using chemical solvents. Naturally refined oils, those that have had heat-sensitive particles removed, tend to oxidize less during cooking than unrefined varieties, even though unrefined oils preserve more of their nutritional value when used raw.

The hidden exposure problem

Even if you never cook with seed oils at home, you are likely consuming far more of them than you realize.

Seed oils are the backbone of ultra-processed food manufacturing. They turn up in crisps, crackers, biscuits, ready meals, sauces, salad dressings, fast food, and almost every packaged snack on supermarket shelves. Soybean oil alone accounts for a significant portion of daily fat intake for many people, often without them ever being aware of it.

This hidden exposure is exactly why cutting back on ultra-processed foods is such a powerful step. When you eat more whole, minimally processed foods, you naturally reduce your seed oil intake, without needing to scrutinize every single label.

A practical guide to better oils

Switching your cooking oils does not require a complete kitchen overhaul, just a few intentional choices. Here is a straightforward guide: