Are Seed Oils Bad for You? Is Beef Tallow Better? I Asked a Dietitian

Only in the last few years did I become aware of the term "seed oils." Like many others, I first heard it through social media — mainly from influencers who claim they're "toxic" and responsible for the rise in chronic illnesses like diabetes, obesity and heart disease.

Yikes.

Was any of this true, and what exactly are these "seeds" from which oil is made? Digging, I soon found the answer: seed oils are a newfangled term for refined plant-based vegetable oils, including canola (yes, it's a seed), corn, sunflower and grapeseed oils.

But I thought vegetable oil is supposed to be healthy for you, at least better than butter or beef tallow, the latter of which several restaurants have recently announced will replace their traditional fry oil. I needed clarifying.

So I turned to Amanda Beaver, a registered dietitian at Houston Methodist, who believes the discussion on fats, including which to use and which to avoid, is "way more nuanced" than many of the blanket statements made on social media and in the news.

"Painting all seed oils as either good or bad for you is a major oversimplification of a very complex subject," says Beaver. "Seed oils do have their drawbacks, especially when compared to others like extra virgin olive oil and avocado oil, but studies have shown that seed oils may still be better for our health than saturated fats like butter, beef tallow and even coconut oil, which can raise our bad cholesterol and increase the risk of heart disease."

As the controversy surrounding seed oils grows, Beaver helps separate myth from fact and offers helpful tips on picking the right fat for the cooking job.

What exactly are seed oils?

Seed oils are the fats extracted from the seeds of various plants and primarily comprise what is commonly labeled as "vegetable oil." In addition to the four already mentioned oils, they also include cottonseed, soybean, safflower and rice bran oils. Critics refer to them as "the hateful eight."

Typically, they're made by crushing the seeds and squeezing out the oil. Stop there, and you'll have something akin to extra-virgin olive oil.

However, even after pressing, a significant portion of oil remains trapped in the seeds, in which case they most often undergo a second or third exaction using heat and chemical solvents to draw out nearly every last drop. After that, the oil is refined, which removes both impurities that can lead to spoilage and unpleasant odors that can impart off-flavors. Beaver says such refining isn't necessarily a bad thing.

"Refining an oil will make it more stable at higher cooking temperatures and give it a more neutral taste," she says. "This can be a good thing if we want an oil not to smoke when we are trying to stir fry or grill with it."

What results is a shelf-stable cooking oil mainly comprised of two unsaturated fats, omega-6 and omega-3 fatty acids, both of which Beaver notes our bodies cannot make but are essential for healthy function. Therefore, we must get them from our diet.

Seed oils tend to be highest in omega-6s and lower in omega-3s compared to other plant-based fats like olive oil and avocado oil, which have a relatively lower amount of omega-6s compared to "seed oils."

The controversy behind seed oils

Seed oils have become a scapegoat of sorts for a host of health issues, and according to Beaver, it boils down to what our body does with omega-6 fatty acids versus omega-3s.

The reason why people "fear" omega-6 fats is that they're associated with the formation of inflammatory compounds within the body, she says. Linoleic acid — the main omega-6 in seed oils — is a precursor to arachidonic acid, which is considered pro-inflammatory.

On the other hand, linolenic acid — the main omega-3 also found in seed oils just at lower levels — can be made into EPA and DHA, both of which are anti-inflammatory in nature.

"The formation of inflammatory compounds sounds like a very bad thing," Beaver says. "However, the amount of omega-6 fats actually converted into these arachidonic acid is very small. Also, arachidonic acid is used by the body for several functions, not all of them bad."

(Related: What is an Anti-Inflammatory Diet?)

"Furthermore, higher intakes of omega-6 fatty acids have not been shown to significantly increase inflammatory markers," she adds. "However, there have been studies linking a higher ratio of omega-6 to omega-3 fatty acids to adverse health outcomes, including an increased risk of mortality from cancer and cardiovascular disease."

All of these arguments, however, tend to get lost in technicalities, says Beaver, and in the case of seed oils, correlation does not always equal causation.

"While the amount of refined seed oils has increased in our diet, so has added sugars, ultra-processed foods and sedentary lifestyles," she says. "It's oversimplifying things if we paint seed oils as the main culprit in the rising rate of chronic diseases like heart disease, diabetes and cancer."

"Seed oils are simply not the demon that social media paints them to be," she adds. "Just because a food has a little bit of a seed oil in it doesn't necessarily mean it's bad for you, and just because a food is seed oil-free doesn't make it healthy either."

(Related: PODCAST: Is Low-Grade Inflammation the Hidden Culprit Behind Chronic Disease?)

Seed oils can't take the heat

Seed oils have a remarkably high smoke point. For instance, refined safflower oil has a smoke point of 510 degrees Fahrenheit, one of the highest among cooking oils. However, smoke point isn't the same as oxidation, when the oil becomes rancid and creates compounds that are "not good for our health," according to Beaver.

Seed oils are more prone to turning rancid, especially in high heat cooking like grilling, stir-frying and broiling, says Beaver. Even the ones with high smoke points, including grapeseed oil, safflower oil, and regular sunflower oil, are not recommended for such applications, she says.

Seed oils' risk of oxidation has to do with their high levels of polyunsaturated fats, a type of unsaturated fat that's more prone to turning rancid due to its molecular makeup. The risk is also due to a lack of antioxidants, which were stripped during the refining process. Heat — especially high heat — makes these bonds more susceptible to breaking down into harmful compounds.

What Beaver instead recommends for high-heat cooking is avocado oil. It has a high monounsaturated fat content — about 70 percent by volume — which makes the oil less prone to oxidation due to its slightly different molecular bond structure. It also has a smoke point of 520 degrees F, making it a great option for high-heat cooking.

"Letting smoke point be your only guide for high-heat cooking might not give you a complete picture on the best oil to use," Beaver says. "It just speaks to when the oil will begin to smoke, which isn't a good thing for your health either."

Similar in antioxidant activity and monounsaturated fat percentage is extra virgin olive oil (EVOO). EVOO can still be used for sautéing and roasting (contrary to what many say) as the antioxidants will help protect the oil from oxidizing. However, if your goal is to preserve more of the antioxidants in the oil, Beaver recommends leaving it for lower-heat applications, such as in dressings, braising or steaming.

Not all seed oils are created equal

Despite the fact many seed oils should not be used in high-heat cooking, some seed oils are better than others, says Beaver.

"High-oleic sunflower oil is very high in monounsaturated fats and lower in omega-6s than regular sunflower oil and happens to be found in a lot of different foods in our foods supply," she says. "You can try looking for it on nutritional labels to see what I mean."

"Canola oil is also much higher in omega-3 fatty acids compared to other seed oils, but I would still not recommend cooking with it in high-heat applications because it's more likely to oxidize during the cooking process," she continues.

Beaver says flaxseed oil and walnut oil also should only be used for low heat cooking. Even though both are high in omega-3 fats, they tend to oxidize very easily.

Ultimately, Beaver recommends seed oils be used in low- to medium-heat cooking applications, like sautéing or simmering — or using them in preparations, like salad dressings and cold dishes, that do not require cooking.

(Related: What's the Best Cooking Oil? Compare Popular Options)

Saturated fats are not good alternatives

Remember 10 years ago when coconut oil was all the rage? Not only were people cooking with it, but people were even swishing it like mouth wash and swirling it into their coffee.

Believe it or not, canola oil went through a similar rise in America during the early '90s. It was the fat that replaced beef tallow in most restaurants, notes Beaver.

Now, beef tallow is having a resurgence as the fat du jour (and not just as a replacement for seed oil in restaurants — in the latest viral trend, people are actually smearing beef tallow on their face as a moisturizer). But dietary swaps of unsaturated fats for saturated ones like beef tallow and coconut oil can have real health consequences, according to research.

A recent study, published in the journal JAMA Internal Medicine and involving more than 200,000 adults, concluded that a higher intake of plant-based oils — including seed oils — was associated with an estimated 17 percent reduction in total mortality. A high butter consumption, on the other hand, was associated with a 15 percent higher risk of total mortality.

"A diet rich in saturated fats versus unsaturated fats is associated with poor health outcomes, including higher risk of heart attacks and stroke, some cancers and even Alzheimer's disease," says Beaver. "However, new research suggests that foods high in refined carbs, added sugar and saturated fats may even be worse for our diet."

These ingredients are most present in ultra-processed foods, which Beaver recommends limiting as much as possible.

The real culprit

Rather than worrying whether a food has seed oils in it or not, Beaver ultimately wants people to focus on eating minimally processed and whole foods as much as possible, including fruits, vegetables, nuts, seeds, beans, lean proteins and whole grains.

"I feel like this seed-oil hysteria is distracting from the larger problem that too many ultra-processed foods have infiltrated the American diet," she says. "Not the fact that a particular food happens to have a little seed oil in it somewhere on the ingredients label."

(Related: PODCAST: We're Eating More Ultra-Processed Foods Than We Think)