Do seed oils really cause inflammation? We asked the experts – Stylist Magazine

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All of a sudden, everyone’s talking about seed oils. On Instagram, certain influencers claim that these oils—pantry staples such as sunflower seed oil, grapeseed oil, and canola oil—cause everything from obesity to diabetes, and others in the wellness space have asserted that “the Hateful 8,” as they’re known, are “slowly killing you” and “the most destructive force in the world today.” Robert F. Kennedy Jr. (president-elect Donald Trump’s pick to head up the Department of Health and Human Services) has been shouting from the rooftops that, as a nation, we are being “unknowingly poisoned” by them.

But before you purge your pantry and start cooking with beef tallow, rest assured: The science simply does not back up these claims. In fact, decades of research point to a very different story—one in which seed-oil consumption is linked to vastly beneficial health outcomes. Here’s our expert-backed reality check.

What are seed oils, anyway?

Technically, a seed oil is a cooking oil made by pressing seeds to extract the fat. But the current pariahs are canola, corn, cottonseed, grapeseed, soy, rice bran, sunflower, and safflower oils. They’re popular ingredients because most are neutral in taste and relatively cheap to produce, and they have a high smoke point. They’ve grown steadily in popularity since the late 1800s, when techniques for extracting the oil were improved, notes Walter C. Willett, MD, a professor of epidemiology and nutrition at Harvard University.

Unlike animal fats such as butter, lard, and beef tallow (which RFK Jr. claims is a vastly healthier alternative), many seed oils are made up of unsaturated fats, and most contain high levels of either omega-3 or omega-6 fatty acids. These polyunsaturated fats are linked to a whole host of health benefits.

What kinds of health benefits?

The effects of seed oils on our health are widely studied, with the results overwhelmingly linking their consumption with improved health outcomes. “There’s 75 years of data backing this up, and it’s among the most rock-solid data out there,” says Christopher Gardner, PhD, a professor of medicine at Stanford University. Like many experts, he’s baffled by the demonization of these oils: “It’s just mind-boggling,” he says.

Since the 1970s, Willett and a team at Harvard have been studying types of dietary fat, tracking over 200,000 people for more than four decades to monitor the impact of nutrition on the incidence of heart disease, diabetes, cancers, and dementia. “Seed oils are inherently much healthier than animal fats, which have a much higher saturated fat content,” he says.

According to Willett, the benefits predominantly stem from the polyunsaturated fats in these oils. In the 1950s, when heart disease rates were at their highest, about 2 percent of calories consumed by Americans came from polyunsaturated fats. This has since increased to about 7 percent—which coincides with a life expectancy increase of 10 years and a dramatic 80 percent drop in fatal heart disease. After studying the potential causes of this reduction, Willett determined that the “most important single change was the likely increase in polyunsaturated fat from seed oils in our diet. Our long-term studies followed hundreds of thousands of men and women, and polyunsaturated fat is strongly related to lower risks of heart disease and total mortality.”

A recent study published in the Journal of the American Medical Association Internal Medicine studied more than 400,000 people over a 24-year period. It showed that replacing just 5 percent of dietary animal fat with plant fat was associated with a 4 to 24 percent lowered overall risk of mortality.

So why all the hate?

One reason seed oils have been targeted by certain corners of the Internet is that they are a common ingredient in many ultra-processed foods, which are undeniably unhealthy. “The reason seed oil intake in America has gone up is not because we’re having more dressed salads or sautéing more vegetables; it’s because we’re eating more junk food,” says Gardner. “Those foods have a tremendous amount of sodium, added sugar, and refined grains in them. But people are saying, ‘Seed oil consumption has doubled in the last few years, and chronic diseases are an increasing problem, so it must be the seed oils.’” Again, the science simply does not back this up, he notes.

Another big claim from some wellness influencers is that the omega-6s contained in seed oils increase inflammatory markers in the body, which can cause symptoms such as joint pain and fatigue. Not so, says Willett: “That’s completely bogus—omega-6 fatty acids do not increase inflammation. There’s a huge amount of literature with randomized trials looking at intakes of omega-6s and inflammatory factors in the blood, and about half the studies show no effect, while the other half actually show benefits or a reduction in inflammatory factors.”

It’s difficult to trace the original source of these “seed-oil conspiracy theories,” as Gardner calls them, but they’ve been circulating on social media for several years. “Certainly, because of RFK Jr., they’ve really taken off,” he says. “It’s one of the more disturbing positions that he’s taken, partly because it’s one of the easier ones to refute.”

Willett, too, remains perplexed by the social media storm: “It’s an interesting sociological phenomenon,” he says. “People are always looking for some demon that’s the cause of their problems.”

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