The major US and international evidence does not back the claim that seed oils harm your health, according to the American Heart Association and the Harvard T.H. Chan School of Public Health.
Both institutions say replacing saturated fats like butter and beef tallow with unsaturated plant oils actually lowers LDL, the kind of cholesterol linked to heart disease.
The Harvard page recommends that 8 to 10 percent of daily calories come from polyunsaturated fat, with evidence supporting up to 15 percent in place of saturated fat.
What the big heart studies actually found
The strongest test of this question comes from a 2018 Cochrane review that pooled 49 randomized trials with 24,272 people. Increasing polyunsaturated fat probably cut the risk of a coronary heart disease event from 14.2 percent to 12.3 percent over the study period.
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Cochrane found little or no effect on overall death rates, so the benefit is modest, not miraculous. But the direction is clear. Swapping some saturated fat for the fat in seed oils helps the heart, not the opposite.
A Harvard analysis published in JAMA Internal Medicine followed more than 200,000 US adults for 33 years. Replacing 10 grams of butter a day with plant oils was tied to a 17 percent lower risk of death from any cause.
The inflammation claim does not match the human trials
The loudest MAHA claim is that linoleic acid, the main omega-6 fat in seed oils, drives inflammation. A 2017 meta-analysis in Food & Function pooled 30 randomized trials with 1,377 participants and tested exactly that.
Higher linoleic acid intake did not change blood levels of inflammatory markers like interleukin-6, tumor necrosis factor or C-reactive protein, a common blood marker of inflammation.
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The authors concluded that increasing dietary linoleic acid does not have a significant effect on inflammation markers in people.
Even the MAHA report published in May 2025 stopped short of calling seed oils harmful. Its own text describes the omega-6 to omega-3 ratio as a topic of ongoing research.
Legitimate nuance still remains
Two caveats are honest. One, oils reused at very high heat for a long time can oxidize and form compounds that are not good for you.
At normal home cooking temperatures, this is not the problem social media makes it. Pick refined canola, sunflower or avocado oil for high-heat frying, and extra virgin olive oil for salads and lower-heat cooking.
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Two, most Americans eat a lot of linoleic acid and relatively little omega-3. The research-backed fix is to eat more omega-3 sources like fatty fish, walnuts and flaxseed, not to banish seed oils from the kitchen.
Olive oil remains the oil with the strongest long-term outcome data and is a reasonable default when heat is not extreme.
The practical takeaway from the AHA and Harvard is simple. Use plant oils in place of butter, lard and beef tallow, favor olive oil where it works, and keep fish, walnuts and flaxseed in your weekly rotation for the omega-3 side of the balance.
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This article is made and published by Ida-Marie Palm Varbæk, who may have used AI in the preparation.