The Skinny on Seed Oils

There’s been a ton of buzz around seed oils over the past few years. Indeed, a November 2024 survey conducted by the International Food Information Council (IFIC) found that three out of four Americans surveyed had some familiarity with the term “seed oils.”

A quick search through social media platforms turns up a bevy of information that insists seed oils are toxic — or that they contribute to a variety of chronic health conditions. 

But is there any truth to these claims? Are seed oils actually bad for you? And should you cut them out of your diet?

The answers to these questions are far more nuanced than some influencers would have you believe. 

We wanted to get to the bottom of the seed oil debacle, so we took a deep dive. Read on to learn more about what seed oils are, their potential benefits and risks, and whether you should eliminate them from your diet.

When we talk about seed oils, we’re referring to a specific group of vegetable oils. Rather than  extracted from nuts (i.e. peanut oil) or the flesh of a fruit (i.e. olive oil), seed oils are made from plant seeds.  

Have you heard of “The Hateful Eight”? No, we’re not talking about the 2015 Western directed by Quentin Tarantino. Detractors of seed oils have coined this term to describe eight of the most common seed oils. These include: 

1. Canola oil, also known as rapeseed oil

2. Corn oil

3. Cottonseed oil

4. Grapeseed oil

5. Rice bran oil

6. Safflower oil

7. Soybean oil

8. Sunflower oil

Seed oils are liquid at room temperature and can be used in many different types of cooking. Their high smoke point makes them ideal for high-heat cooking applications, such as sautéing, roasting, stir-frying, and deep-frying. 

Seed oils have other food uses as well: They’re often used as a base for homemade salad dressings, and they’re often included s in various processed and ultra-processed foods. 

Nutritionally speaking, seed oils are high in polyunsaturated fatty acids (PUFAs). The term “polyunsaturated” refers to the nuances of their chemical makeup. 

In the body, PUFAs are vital components of cell membranes. They’re also involved in pathways related to inflammation, blood clotting, and the widening and narrowing of blood vessels. 

The two main types of PUFAs are omega-3 fatty acids and omega-6 fatty acids. Seed oils contain high levels of omega-6 fatty acids. 

Both omega-3 and omega-6 fatty acids are essential fatty acids. Your body needs to get adequate amounts of both from dietary sources because it cannot make them on its own. 

Let’s start out with some good news. There are some health benefits associated with omega-6 fatty acids and, by extension, seed oils. 

For instance, the American Heart Association notes that omega-6 fatty acids can play a role in reducing heart disease, and therefore supports their inclusion as a part of a healthy diet. 

A 2020 analysis of a cohort of over 68,000 people found that higher levels of omega-6 fatty acids in the body were associated with a lower risk of major cardiovascular events like heart attack and stroke. 

A 2025 systematic review focused specifically on 11 studies of seed oils in people with dyslipidemia or type 2 diabetes. The results suggest that seed oils may have a positive influence on blood lipid levels and blood sugar control. 

There’s a lot of talk about the potential health risks of seed oils. If you’re wondering if there are health risks associated with seed oils, well, the answer is a bit complicated. Let’s dive in. 

Extracting and Refining: Concerns About How Seed Oils Are Produced

The first step in making seed oils is extracting the oils from the seeds. This is typically done using a solvent called hexane. 

On a very basic level, hexane helps to separate the oil from the seed. The hexane is then evaporated off, leaving the seed oil behind. Some critics of seed oils claim that there’s still some hexane remaining in seed oils, which could be toxic. 

“None of these claims are well-founded in scientific literature,” says Emily Villaseca, RDN. She points to a 2017 study that analyzed 40 samples of seed oils collected from 23 brands. While the researchers detected hexane residues in almost all of the samples, the levels were below the limit set by the European Union (EU). 

“To put this into perspective, our daily exposure to hexane from sources like gasoline fumes is significantly higher than the minimal amounts found in all the food and ingredients we consume,” Villaseca says. “The greatest concern of hexane-related health risk is in those who are regularly exposed to hexane fumes in workplaces, not in those exposed to trace amounts from food sources.”  

After extraction, seed oils are refined. This process helps to remove potential contaminants and substances that could affect the taste, odor, or shelf life of the oil. 

However, the refining process also removes some healthy nutrients from the oils. These include things like antioxidants and polyphenols. Depending on the refining process used, undesired compounds, such as trans fats, may also form. Beyond the omega-6 fatty acids they contain, seed oils are lacking in other beneficial nutrients.  

Seed Oils and Inflammation: The Low-down

A lot of the talk around seed oils mentions the potential for the ingredient to be pro-inflammatory. And because inflammation is associated with many chronic conditions from cardiovascular disease to cancer, seed oils get a bad rap. 

Linoleic acid is an omega-6 fatty acid that’s found at high levels in seed oils. Our bodies can convert it into arachidonic acid, which is involved in the production of inflammatory molecules in our body. 

So the logic goes: consuming high levels of linoleic acid can increase levels of arachidonic acid and therefore boost inflammation. But this isn’t exactly true.  

Previous research has found that increasing dietary intake of linoleic acid is not associated with increased arachidonic acid in the blood. 

A later 2017 systematic review and meta-analysis of 30 studies supported this finding, concluding that higher linoleic acid intake didn’t have a significant effect on inflammation markers in the body. 

“Seed oils are often thought to contribute to inflammation because most, but not all, are higher in omega-6's and have a higher ratio of omega-6 to omega-3 fatty acids,” says Romy Nathan, MPH, RDN. “But scientific evidence suggests that omega-6 fatty acids can provide cardiovascular protection.” 

The Omega-6 to Omega-3 Fatty Acid Ratio, Explained

You may also hear talk of  the omega-6 to omega-3 ratio. This “ratio” refers to a person’s intake of omega-6 fatty acids compared to their intake of omega-3 fatty acids. 

Some research suggests that early humans evolved on a diet where intake of omega-6 and omega-3 fatty acids was equal, a 1:1 ratio. A current typical Western diet now typically includes much more omega-6 fatty acids, leading to a very lopsided ratio of 16:1. 

Indeed, consumption of omega-6 fatty acids has increased over the past century or so. For example, a 2011 study found that the estimated per capita increase in the consumption of soybean oil, a seed oil, increased over a thousand-fold from 1909 to 1999.

Omega-6 and omega-3 fatty acids are broken down by the same enzymes in the body. Omega-6 fatty acids like linoleic acid are broken down into arachidonic acid, which has inflammatory properties. Meanwhile, omega-3 fatty acids are broken down into eicosapentaenoic acid, which has anti-inflammatory properties. 

Some voice concern that consuming more omega-6 fatty acids than omega-3 fatty acids may lead to a lower metabolism of omega-3 fatty acids in the body. This could lead to a higher amount of arachidonic acid, increasing inflammation. 

There is some research that supports the suggestion that a higher omega-6 to omega-3 fatty acid ratio is linked to negative health effects. A 2024 cohort study that used data from the UK Biobank found that a higher omega-6 to omega-3 ratio increased the risk of death from cardiovascular disease and cancer. 

That said, research into this topic is still very limited. We’ll need additional studies to understand how exactly the omega-6 to omega-3 fatty acid ratio may impact health and wellness. 

And, as we’ve already covered, other studies have found that increased linoleic acid intake doesn’t appear to boost inflammation levels. 

Seed Oils and Chronic Disease: It’s Complicated

Another claim about seed oils is that they increase the risk of a variety of chronic diseases. The available research on the subject has mixed findings.  

For example, a large 2022 systematic review and meta-analysis conducted by researchers at the World Health Organization (WHO) looked at PUFA intake and the risk of death and several chronic health conditions, including cardiovascular disease, breast cancer, diabetes, mental health disorders, and inflammatory bowel disease.

When the researchers analyzed the available data on omega-6 fatty acids, they found: 

• Overall, an increased total omega-6 fatty acid intake was associated with a 9% reduced risk of death, but a 31% increased risk of postmenopausal breast cancer.

• A high intake of linoleic acid was linked with several health benefits, including a 16% reduced risk of death, a 17% lower risk of fatal cardiovascular disease, and a 14% reduced risk of coronary heart disease. However, it was also linked with a 26% increased risk of depression.

• Increased arachidonic acid intake was associated with a 5% increased risk of breast cancer. 

As you can see, the analysis supports the suggestion that omega-6 fatty acids can be beneficial for heart health. But, simultaneously, research suggests these fatty acids may increase the risk of other medical conditions like breast cancer or depression. This is another topic area that needs more study before any firm conclusions can be drawn. 

Seed oils are often criticized for being associated with weight gain. But weight gain isn’t an issue strictly limited to these ingredients.  

“Seed oils, like any source of fat, contribute calories to the diet, and weight gain occurs when there is a consistent calorie surplus—not simply from consuming seed oils,” says Rene Ficek, RDN.   

“Some seed oils, such as canola and soybean oil, contain unsaturated fats that can support heart health and satiety when consumed in appropriate portions,” she continues. “However, seed oils are frequently used in highly processed [or ultra-processed] foods, which tend to be calorie-dense and low in nutrients.” 

Ultra-processed typically include added salt, sugar, or fat to enhance flavor, texture, and storage time, along with additives like artificial sweeteners, colors, and flavors as well as preservatives and emulsifiers. In addition to fast food and fried foods, examples of other ultra-processed foods include: 

• Sodas and other sugar-sweetened beverages

• Packaged snacks like potato chips and crackers

• Meat products like hot dogs and other sausages, chicken nuggets, and fish sticks

• Mass-produced bread, cookies, cakes, and pastries

• Pre-made meals, such as frozen pizzas or pastas

• Breakfast cereals

• Instant soups

• Candy 

Americans eat a lot of ultra-processed foods.. Researchers have found that ultra-processed foods account for over 50% of a typical American adult’s calorie intake. 

Ultra-processed foods are linked to increased inflammation as well as to a variety of other health issues. For one, they tend to lead to a higher intake of calories as well as weight gain, contributing to obesity. Further, research has linked ultra-processed food consumption to a higher risk of many different health problems, including cardiovascular disease, type 2 diabetes, and mental health disorders. 

While it’s true that the majority of ultra-processed foods contain one or more seed oils, they also contain high amounts of saturated fat, added sugars, and sodium and often provide lower amounts of important nutrients like protein, fiber, and vitamins and minerals. 

So can seed oils lead to weight gain? Technically yes, but there’s more to the story. 

Villaseca says it can be helpful to consider the source of the seed oils you consume. Doing so can give you more information about the overall healthfulness of what you’re eating. “Seed oils are commonly used in fried and processed foods, which we already know are usually higher in calories, salt, added sugar, and unhealthy fats,” she says. Thus, it’s not necessarily the seed oils themselves that are leading to weight gain, but the foods they’re often associated with.

In summary, the effect of seed oils on weight is just one piece of a larger, more complex puzzle that encompasses diet and other lifestyle choices. 

If you’re looking into alternatives to seed oils, you’re in luck. “The good news is, if you would like to lower your exposure [to seed oils], you have several options,” says Villaseca. “You can opt for olive oil or avocado oil, which are also very widely available.” 

Olive oil is an important component of the Mediterranean diet and contains mainly monounsaturated fatty acids. The consumption of olive oil is associated with a reduced risk of cardiovascular disease, type 2 diabetes, and cancer. 

But olive oil might not be the best pick for all occasions, since it has a lower smoke point than many other plant-based oils. That means that it may be less appropriate for the types of high-heat cooking that seed oils are often used for.

 For high-heat situations, avocado oil may fit the bill. Like olive oil, avocado oil is rich in monounsaturated fatty acids. Its higher smoke point makes it more adaptable for high temperature-cooking. 

What About Animal Fats?

Some detractors of seed oils recommend using animal fats like butter, lard, or beef tallow as cooking alternatives. But some research suggests that making these substitutions may do more harm than good. 

For example, a 2025 cohort study published in JAMA Internal Medicine found that a higher butter intake over time increased the risk of death. The researchers found that the highest level of butter intake was associated with a 15% increase in the risk of death. 

Meanwhile, the highest intake of plant oils was linked with a 16% reduced risk of death. A higher intake of olive oil as well as canola and soybean oils, both seed oils, were associated with a lower risk of death.

Before you go dumping out all of your seed oils, hold the phone.  

“There is no strong scientific evidence to support eliminating seed oils entirely,” Ficek says. “These oils provide essential fatty acids, such as omega-6s, which play a role in inflammation regulation and cellular function.”  

Rather than completely omitting these ingredients from your diet and kitchen, consider taking a more moderate approach. “While balancing omega-6 and omega-3 intake is important, completely avoiding seed oils is unnecessary and may lead to an overly restrictive diet,” Ficek says. “Instead, a more beneficial approach is to focus on reducing intake of highly processed foods, where seed oils are often found, and prioritizing whole, minimally processed foods.”  

At the end of the day, it’s unlikely that using canola oil to cook your favorite stir-fry recipe will lead to lasting health problems. 

If you do want to cut back on seed oils a bit, you could try subbing in different oils for cooking and increasing your intake of omega-3 fatty acids. 

Intake of omega-3 fatty acids, especially when they come from fish, can help prevent cardiovascular disease, and may lower the risk of dementia and the risk of some cancers. 

Good sources of omega-3 fatty acids include fish like salmon, mackerel, tuna, herring, and sardines. Plant-based sources of omega-3s include flaxseed oil, chia seeds, and walnuts. 

Another great way to cut back on seed oils is by lowering your intake of ultra-processed foods. Instead, focus on whole foods that are unprocessed or minimally processed. 

Nathan agrees. “Rather than thinking about ratios, it would be more beneficial to think about balance and increase your intake of omega-3s to make that balance better,” she says. “Ultra-processed foods contain lower quality oils and often excessive omega-6s. Reducing these and increasing whole foods alone will increase diet quality and balance.”  

We’ve covered a lot of different information about seed oils. Here’s a highlight reel to review:  

• Seed oils are extracted and refined from the seeds of various plants. Common seed oils include canola oil, corn oil, and soybean oil.

• Seed oils are a source of polyunsaturated fats, particularly omega-6 fatty acids like linoleic acid.

• Omega-6 fatty acids can reduce heart disease risk and may also help manage cholesterol levels and blood sugar. The American Heart Association recommends them as part of a healthy diet.

• The refining process can strip seed oils of potentially beneficial nutrients like antioxidants.

• While linoleic acid can be broken down into arachidonic acid, which has inflammatory properties, there’s not any firm evidence to suggest higher linoleic acid intake drastically increases inflammation.

• Higher ratios of omega-6 fatty acids relative to omega-3 fatty acids may have a negative effect on health, but more research is needed.

• While a higher intake of omega-6 fatty acids may boost heart health, it may increase the risk of other medical conditions like breast cancer or depression. Again, further study is necessary.

• Seed oils are present in ultra-processed foods, which are linked with a higher risk of weight gain, heart disease, and type-2 diabetes. Ultra-processed foods also typically have high levels of saturated fat, added sugar, and sodium and low levels of protein, fiber, and other important nutrients.

• Olive oil and avocado oil are good substitutes for seed oils. However, be wary of subbing in things like butter, which could have harmful health effects when used in excess.

• You can reduce your intake of seed oils by focusing more on omega-3 fatty acids and aiming to lower your intake of ultra-processed foods. Most experts agree that omitting these oils entirely from your diet isn’t necessary for most. 

The TL;DR of seed oils and your health? No, seed oils aren’t necessarily bad for you and they certainly aren’t toxic. 

However, you may still wish to reduce your use of seed oils and that’s totally okay, too. If that’s the case, we recommend consulting with a nutritionist or dietitian to ensure you’re replacing seed oils with healthy alternatives as part of a balanced diet. 

Looking for a recipe that doesn’t include seed oils and is still packed with flavor and nutrients? Check out our Mediterranean salad recipe, which is dressed in heart-healthy olive oil (and is truly delicious!).