Are Seed Oils Bad for You?

We asked experts to weigh in on some of the claims you may have been hearing on the internet.

April 27, 2023

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Photo by: annick vanderschelden photography/Getty Images

annick vanderschelden photography/Getty Images

Perhaps you’ve heard about the so-called health risks of seed oils, and then started noticing them on ingredient labels of foods like hummus and peanut butter. But are seed oils really bad?

It’s a confusing topic. There’s a lot of seed oil hype swirling around the internet and social media. Here’s the straight scoop.

What Are Seed Oils?

Seed oils are simply the oils that come out of oil-rich seeds when they are pressed. Seed oils include canola, sunflower, grapeseed, cottonseed, safflower, soybean and corn oils.

All these oils are made up of primarily unsaturated fats, that is, both monounsaturated and polyunsaturated fats in unique amounts. They also contain much smaller amounts of saturated fats.

Are the Polyunsaturated Fats in Seed Oils Bad

Some seed oils contain more monounsaturated fats than polyunsaturated fats; these include canola and safflower oils.

Sunflower, corn, soybean and cottonseed oils contain more polyunsaturated fats than monounsaturated. Polyunsaturated fats are also known as PUFAs.

PUFAs include both omega-3 fatty acids and omega-6 fatty acids which your body cannot make and are considered essential nutrients required by humans. The most common of these PUFAs is the omega-6 fat known as linoleic acid. Once metabolized, the body uses linoleic acid for building membranes for cell structures and may act as signaling molecules.

Despite these important functions, in the past, linoleic acid was linked with inflammation. Part of this was due to a misunderstanding of the inflammation process. Linoleic acid is part of the acute inflammation response (good inflammation when the body is cut or bruised), but it’s not part of chronic inflammation (associated with chronic disease). Furthermore, new discoveries of the many derivatives that can form from linoleic acid has revealed some of its acute inflammatory job is to lower inflammation, or resolve inflammation, as part of the healing process.

“Linoleic acid does not cause chronic inflammation and has many functions beyond a role in acute inflammation,” explains fatty acid expert Martha Belury, PhD, RD, researcher at The Ohio State University.

There is now widespread scientific agreement that linoleic polyunsaturated fats do not lead to chronic inflammation. In fact, for over 70 years, scientists and clinicians have recognized that linoleic acid is actually linked to a reduced risk of heart disease. The American Heart Association issued a presidential advisory stating that limiting linoleic acid would do more harm than good.

So, Are Seed Oils Good for You?

Most of us need to eat more polyunsaturated fats in order to get more linoleic acid. Seed oils are an excellent source of polyunsaturated fats.

Contrary to some of the information on the internet, plant seed oils are linked to heart health, decreased risk of diabetes and decreased inflammation. Additionally, a serving of 1.5 tablespoons of soybean oil qualifies for a heart health claim.

Researchers found in this double-blind study, that people with diabetes who ate 1.5 tablespoons of seed oil for four months had improved blood sugars and decreased inflammation.

Similar results were found in this research review which examined 20 studies and found that higher linoleic fatty acids in the blood (a marker for higher consumption of oils like soybean, canola and safflower) was associated with better blood sugars, increased insulin sensitivity, and less incidence of diabetes.

“The link between higher linoleic acid and reduced risk for type 2 diabetes may be due to its role to increased insulin sensitivity and a lower risk for central obesity and other conditions linked to chronic inflammation,” notes Belury.

Does Industrial Processing Make Seed Oils Bad?

All fat molecules (saturated, PUFAs and monounsaturated) are arranged as chains of carbon, hydrogen and oxygen.

By definition, PUFAs are missing two or more hydrogen pairs on their chains. In other words, they have two or more unsaturated double carbon bonds. The more double bonds a fat has, the more likely it is to be damaged by heat, light and air, and thus become oxidized. That’s why it’s important to store nuts and seeds in the refrigerator or freezer, and keep extra virgin or cold-pressed oils out of the light and away from the heat.

In order to prevent cooking oils from quickly turning rancid on your shelf, or to prevent potential oxidation when used in baking, an oil must be processed. Seed oils are heated during processing.

After processing, oils maintain the same fatty acid profile they had in their natural form, straight out of the seed. It’s true that heat-processing leads to the loss of some of the vitamins A and vitamin E and other seed antioxidants. However, the heat is not high enough to cause oxidation or rancidity, or make a seed oil more unstable than it was in nature.

What About Seed Oil Hydrogenation?

Previously, manufacturers partially hydrogenated polyunsaturated fats to make them solid and much more shelf-stable in packaged foods like baked goods, crackers, snack chips, margarine and salad dressing.

“When oils are hydrogenated, PUFAs are made saturated, a process known as partial hydrogenation,” explains Belury. “The problem with partial hydrogenation is it forms some trans fats along with saturated fats. It is recommended that less than 10 percent of our calories come from saturated fat, and Americans are way over that. Recommendations are to avoid trans fats all together. The reason for avoiding trans fats is they are highly correlated to increased risk for heart disease and possibly other diseases like type 2 diabetes.”

The FDA banned partially hydrogenated fats in 2018, and the ban was finalized in 2021.

Fully hydrogenated fats are another different fat. They are still somewhat liquid at room temperature, but much more solid than other unsaturated fats. Importantly, fully hydrogenated oils do not contain trans fats, but they do help prevent oil separation in foods.

Are Foods Containing Seed Oils Okay to Eat?

Yes. Nutrient-rich foods containing seed oils are wholesome choices and can be enjoyed daily; these include peanut butter, hummus and whole grain crackers.

The benefits of eating more legumes certainly outweigh any risks from a few drops of oil (generally less than two percent on the nutrition label) in each serving.

However, seed oils are often a main ingredient in foods like chips, snacking puffs, sauces, marinades, salad dressings and other convenience snacks and meals – and some of these foods are also high in refined carbohydrates, added sugars and sodium. So if these types of foods are replaced with more whole foods, people complaining of ill-health affects may feel better overall, but it’s probably not from eating less seed oils.

Which Seed Oil Is Best for Pan-Frying?

Seed oils like canola, grapeseed, and soybean oil (soybean oil is labeled as “vegetable oil”) are excellent choices for home cooking like sautéing, stir frying and pan-frying. Additionally, cooking vegetables in a few tablespoons of oil helps the body absorb vitamins.

Is it okay to eat French fries or other restaurant food that’s fried at very hot temperatures in oil that’s rarely changed? Not often. To prevent oxidation, cooking oil should never be reused; but often it is in restaurants.

Which Seed Oils Are Best for Baking?

Extra virgin olive oil (not a seed oil) contains the most antioxidants. But canola oil and vegetable/soybean oil are good options in terms of fatty acid contents, and they don’t have the pronounced olive oil flavor.

Bottom Line: It’s not realistic or logical to connect one substance – in this case, seed oils – to a long list of health problems, from headaches to autoimmune disorders. In general, it’s best to eat whole seeds, but for home baking and sautéing, canola, grapeseed and vegetable oils are healthful options. And when you need an on-the-go option, hummus and peanut butter, as well as dried fruits (the oil prevents sticking) and whole grain crackers made with soybean, safflower or other so-called ‘industrial’ oils are nourishing foods to enjoy.

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