Are Vegetable Oils and ‘Industrial Seed Oils’ Unhealthy?

A new food bogeyman is making headlines in the nutrition world: oils, such as canola, corn, and soybean, that are extracted from the seeds of edible plants.

Robert F. Kennedy Jr., the new U.S. secretary of Health and Human Services, is among those alleging that these so-called seed oils are sneakily unhealthy and even downright dangerous.

“Seed oils are one of the most unhealthy ingredients that we have in foods,” said Kennedy during a TV appearance with Fox News. “They are associated with all kinds of very, very serious illnesses, including body-wide inflammation … and it’s almost impossible to avoid. If you eat processed food, you’re going to eat seed oil.”

Yet while seed oils are certainly ubiquitous in ultra-processed foods, the oils themselves have long been considered safe and even beneficial by organizations such as the American Heart Association.

“Seed oils are basically a very healthy part of a diet, and when you look at some of the alternatives — like butter or lard — these are much better,” says Walter C. Willett, MD, DrPH, a professor of epidemiology and nutrition at Harvard T.H. Chan School of Public Health in Boston.

So why are seed oils under attack? And do any potential benefits outweigh possible harms?

What Are Seed Oils?

Nutrition influencers sometimes use the phrase “industrial seed oils” to underscore that most of the vegetable oils in question are manufactured using modern technology.

These influencers often refer to the seed oils they have deemed most hazardous as the “Hateful Eight”:

Demand for these oils has skyrocketed due to their relatively low cost, neutral flavor, and high smoke points — canola oil, for instance, can withstand higher temperatures than olive oil can without burning.

Soybean oil is the most widely used edible oil in the United States, although you might not know that because it’s usually sold under the generic moniker “vegetable oil.”

Rice bran oil is a staple at Asian grocers and other specialty stores.

Because cotton is not a food, it may be hard to imagine its oil as edible. Manufacturers commonly use cottonseed oil, however, for making margarine, salad oils and dressings, potato chips, and other snacks. Fast food chains such as Burger King may rely on cottonseed oil.

Chemicals May Remain in Seed Oils After Processing

Seed oils are sometimes called RBD oils, which stands for refined, bleached, and deodorized, a reference to the industrial extraction processes required to make them edible.

Although manufacturers treat seed oils to remove any harmful chemicals introduced during extraction, trace amounts may remain, says Christopher Gardner, PhD, the director of nutrition studies at the Stanford Prevention Research Center.

Hexane is a major worry of those concerned about seed oil. Manufacturers use this petroleum by-product as the primary solvent for extracting oil from soybean, canola, sunflower seed, and cottonseed.

The U.S. Environmental Protection Agency has identified hexane as an air pollutant and a fire hazard, and notes that it can be harmful when inhaled.

As for hexane consumption, the European Union has set a maximum residual limit of 1 milligram per kilogram (mg/kg) of hexane residue in vegetable oils. The U.S. Food and Drug Administration (FDA), however, does not currently monitor or regulate hexane residue.

“Is the amount of hexane in seed oils hurting us?” asks Dr. Gardner. “From what I read from food scientists, I don’t think so.”

Debate Over Omega-6 Fatty Acid

Another major focus in the controversy over seed oils has been omega-6 linoleic acid.

Seed oils are rich in this fatty acid. Omega-6, like omega-3, is a polyunsaturated fat, which the American Heart Association says can help protect against type 2 diabetes and heart disease by lowering LDL (“bad”) cholesterol and triglycerides.

But some scientists suggest that high amounts of omega-6 lead to the excessive formation of another fatty acid (arachidonic acid), which might promote inflammation and blood-vessel constriction.

Studies have linked high levels of arachidonic acid to obesity, diabetes, autism, Alzheimer’s disease, anxiety, and depression.

Despite concerns about arachidonic acid in high amounts, plenty of other studies highlight its benefits in modest amounts. Harvard Medical School, for example, says that the body converts arachidonic acid into molecules that may actually calm inflammation and fight blood clots.

A number of studies have found no connection between increased omega-6 intake and a higher risk of illness.

In research involving 110,000 men and women who were followed for almost 30 years, Dr. Willett and his colleagues examined the relation of omega-6 polyunsaturated fatty acid intake to the risk of colorectal cancer.

They did not find any increase in cancer risk. On the other hand, they noted a much lower risk of overall mortality in participants with a higher intake of omega-6 fatty acids than in those with lower consumption of omega-6 fatty acids.

Keeping a Balance With Omega-3s

The consumption of omega-6 fatty acids along with omega-3 fatty acids plays a crucial role in brain function, normal growth, and development. Plus, omega-6s stimulate skin and hair growth, maintain bone health, regulate metabolism, and maintain the reproductive system.

But balance is key, and for the typical American, that balance is out of whack. The average American diet tends to contain 14 to 25 times more omega-6 fatty acids than omega-3 fatty acids, when a balance closer to 4 to 1 (omega-6 to omega-3) is likely healthier.

In one study on heart disease prevention, results showed that a more balanced ratio of 4:1 was associated with a 70 percent decrease in total mortality — though this lower risk has not been causally proven.

Still, both Gardner and Willett see concern about the ratio of omega-6 to omega-3 as unfounded.

“At some point, you can probably go too high with omega-6 consumption, but we haven’t seen that in this country,” says Willett.

“Omega-3s are modestly different from the omega-6s in a beneficial way, but not a lot,” adds Gardner. “Omega-6s are required for your health, but somehow the message became twisted to be ‘Omega-3 are more anti-inflammatory, so that means omega-6s are pro-inflammatory’ — which is false,” he says.

Analysis of scientific data from dozens of studies by the American Heart Association concluded that consumption of omega-6 fats is overall beneficial for the heart and circulation, and should be a part of a healthy diet.

“The idea that omega-6 fatty acids are pro-inflammatory is propagated over and over again in social media,” says Willett. “Dozens of studies have looked at this, and about half of them show no effect, while the other half show reduction in inflammatory factors.”

Ultra-Processed Foods May Be More Harmful Than Seed Oils

Gardner points out that studies indicating a harmful effect of omega-6 show an association and not causation, and that the bigger problems may not be from the seed oils but in the foods they are used in.

“One of the statistics that I hear from social influencers is that the consumption of seed oils has increased, and that seems to be in parallel with all kinds of chronic, debilitating disease related to inflammation,” he says. “But I think what it really parallels is the world of ultra-processed foods, which are loaded with sodium, added sugar, and saturated fat.”

So although seed oil consumption is up, the real culprit behind higher incidents of chronic disease and obesity may be the ultra-processed foods that incorporate seed oil.

How to Minimize the Possible Risks of Seed Oils

While debate regarding seed oils is sure to continue, there are measures you can take to make sure you’re eating healthy fats that boost overall health.

The Takeaway