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Seed Oils: Are They Actually Toxic?

Often found in ultra-processed foods, these oils can cause inflammation and diseases

person at grocery store reading oil label

Collectively, the people of the internet are always looking for the next big food trend, the next magic bullet, whether it’s something to add to or remove from our diets to make all of our health problems disappear.

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Nowhere is that tendency more intense than on TikTok, where food-related topics go viral in an instant (and oftentimes, disappear just as quickly). But one of them seems to have some staying power: Warnings of the risks of seed oils.

TikTok health gurus claim that seed oils are toxic, causing everything from acne and weight gain to cancer and infertility. But what’s the truth? As is so often the case, the reality 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 forever or just focus on a healthy, balanced diet (hint: It’s the latter).

What are seed oils?

Seed oils are plant-based cooking oils made from — you guessed it — the seeds of various plants. These seeds (we’ll share the whole list in a moment) are turned into oil that can be used for cooking and baking.

“They’re made through a chemical process where they’re bleached, refined and heated in order to be usable,” Zumpano explains.

You might use seed oils at home, like putting a few tablespoons in a healthy muffin recipe or using one of them to pan-fry some potato pancakes. And these oils are frequently used in restaurants, where canola oil, in particular, is the oil of choice for deep-frying.

What seed oils are included?

Seed oils first emerged in the late 1900s as an alternative to partially hydrogenated oils. Here are the eight seed oils most commonly used and discussed:

  • Canola oil (aka rapeseed oil).
  • Corn oil.
  • Cottonseed.
  • Grapeseed oil.
  • Soybean oil.
  • Sunflower oil.
  • Safflower oil.
  • Rice bran oil
  • Peanut oil.

You might even hear this group of seed oils referred to as the “hateful eight,” a reference to some people’s belief that they’re toxic and should be completely removed from your diet. But is the problem with seed oils themselves or the way they’re used?

“Most seed oils are being utilized in the form of processed packaged foods, fast foods and eating out,” Zumpano says. “That’s where most of the danger lies.”

Let’s dig into that…

Are seed oils unhealthy?

Yes and no (but mostly yes). Because of the way they’re made, seed oils are typically very processed. Even worse than that, though, is they’re usually used to make ultra-processed foods — think fast food burgers and fries and anything you’d eat at a state fair or get in a package in the grocery store.

“Seed oils themselves have high levels of omega-6 fats, which can lead to inflammation.” Zumpano says, “and they’re mostly used to make ultra-processed foods, which causes inflammation in the body.”

Keep in mind that they’re also sometimes added to foods marketed as “healthy,” including whole-grain crackers or bread products, protein bars or shakes, dressings, sauces, some frozen foods and even chocolate.

To better understand what all of that means for your health, Zumpano helps us break down the issues with seed oils and how they’re used.

They’re often very processed

Some of these oils would be high in vitamin E and phenols, if not for the refining process itself. Alas…

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“Most seed oils go through the refining process, which includes bleaching and deodorizing,” Zumpano explains. “This helps with the taste, color and shelf life, but it also removes the oils’ antioxidants.”

The end result is oils with no real health benefits and more than a few health risks.

They’re usually used in unhealthy foods

Seed oils aren’t necessarily good for you. But the real reason they’re considered so bad for you is how they’re most often used.

“Most seed oils are being utilized in the form of processed packaged foods, fast foods and eating out, and even foods that are considered minimally processed but are still packaged,” Zumpano reiterates. And that’s where the danger is.

Outside of your own home, you’re most likely to consume seed oils when you’re eating something that’s already pretty bad for your health — something that’s also full of fat, sugar and sodium. It’s not a bad idea to look in your cupboard, too, as these oils are so abundant that it’s smart to avoid or seriously limit them wherever you can.

They contribute to inflammation in your body

Seed oils are high in omega-6 fatty acids, a type of polyunsaturated fat that isn’t necessarily bad for you. In fact, your body needs a little bit of them! In small amounts, they’re good for your cholesterol and help protect you from heart disease.

But American diets typically already include too many omega-6s. This throws off your body’s ratio of omega-6 fatty acids to omega-3 fatty acids, leading to inflammation in the body.

While a little bit of inflammation is actually a good thing (it’s your body’s way of healing cell damage), chronic inflammation is definitely not. It’s linked to conditions like:

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“If a certain food is high in oils that contain a lot of omega-6s, you really want to try to avoid them or eat them only in moderation,” Zumpano advises.

Should you avoid all seed oils?

If you want to stop consuming seed oils, there are no downsides. But Zumpano says you’d be just as wise to commit to avoiding processed foods instead. It’s a move that will inherently result in scaling back on seed oils, while also allowing you the leeway to use them in small amounts.

“When you cut seed oils from your diet, what you’re really doing is cutting out many processed foods,” she adds. “I think that’s why we’re hearing about them as being so bad for your health. But it’s less about the seed oils themselves and more about the fact that they’re so often found in ultra-processed foods.”

But what about using seed oils at home? Should you throw away that bottle of sunflower oil on your shelf? Experts tend to have varied opinions on this one, but Zumpano believes they should be limited in home cooking.

“They’re not necessarily the greatest choice in oil,” she notes. “But when used in moderation in home cooking, they’re not nearly as bad for you as when you’re getting them in ultra-processed foods, fast foods and fried foods.”

Still, she recommends mostly cooking with alternative oils that provide more omega-3s, like avocado oil or olive oil (more on that in a minute).

And keep in mind, too, that you want to try to increase your omega-3 intake and limit your omega-6s.

“Omega-3s are so important for overall heath that we really need to make the effort to get them into our diets,” Zumpano says. “Omega-6s, on the other hand, are in abundance in Western diets.”

The omega-6 to omega-3 ratio should be ideally 2:1 or 1:1, but for most Americans, the ratio is actually a whopping 10:1 or even 20:1.

If you do want to cook with seed oils at home, use them infrequently and in small amounts. Importantly, you should also buy versions that are pure and unrefined, which aren’t as processed and retain some of their nutrients.

Good substitutes for seed oils

Occasionally frying your breakfast potatoes in a little bit of organic, unrefined sunflower oil isn’t going to throw your body into disarray. But Zumpano says there are healthier oils to choose from, so you’re probably better off just using one of those.

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She recommends using extra-virgin olive oil (EVOO) for low-heat cooking and avocado oil for high-heat cooking. They’re both high in heart-healthy omega-3 fatty acids instead of additional omega-6s.

“Both of these oils are clinically shown to have higher monounsaturated fats,” Zumpano shares. “They’re not seed-based, and they don’t go through the same type of processing, so they’re very unrefined and even have a lot of nutritional benefits.”

Limit your oil use

In general, it’s best to take it easy on oils, both seed and otherwise. And this is especially true when you go out to eat, as most restaurants use cheap cooking oils — which is to say, refined cooking oils.

But instead of focusing specifically on banishing seed oils from your diet, Zumpano reiterates that your first step should be trying to eliminate ultra-processed foods from your diet as much as you possibly can.

“Try to cook at home as often as possible and purchase foods that have simple ingredients,” she says. “That’s always my No. 1 recommendation.”

Doing so will naturally lessen your seed oil intake while not restricting you from, say, going out to dinner with a friend or having a few potato chips at a party. And eating well at home will help offset the times when you eat out and don’t have a handle on every, single ingredient you consume.

“Eating whole, unprocessed foods at home gives you a little bit of a buffer when you go out to eat,” Zumpano says. “If you’re able to maintain and manage what you eat most of the time, then the other times won’t have as big of an impact on your health.”

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