Are Seed Oils Really Causing Inflammation? The Science vs. the Narrative

Seed oils have become the villain of wellness TikTok. Canola oil is basically poison, apparently. Soybean oil is why you're tired, inflamed, and can't lose weight. Except… the actual research is a lot messier than that. The science doesn't really support the panic — but it doesn't fully exonerate seed oils either. Here's what the studies actually say.

What Even Are Seed Oils?

"Seed oils" is a loosely used term for oils extracted from plant seeds — canola (rapeseed), soybean, corn, sunflower, safflower, cottonseed. Sometimes grapeseed and rice bran get lumped in. They're high in polyunsaturated fatty acids (PUFAs), especially linoleic acid, an omega-6 fat. They're in almost every processed food, most restaurant kitchens, and probably your pantry.

Oils like olive and avocado aren't usually called "seed oils" in the wellness world — even though technically olives and avocados are fruits with seeds. The distinction being made is really about highly refined, industrially processed oils versus cold-pressed, minimally processed ones. That distinction matters more than it usually gets credit for.

What Are People Actually Claiming?

The carnivore and ancestral health crowd has made seed oils the centerpiece of a lot of health claims. The arguments generally go like this:

• Seed oils are unnaturally high in omega-6 fatty acids, especially linoleic acid.
• Too much linoleic acid throws off your omega-6 to omega-3 ratio, which promotes inflammation.
• High heat and chemical processing (hexane extraction) creates toxic byproducts like oxidized linoleic acid metabolites (OXLAMs) and aldehydes.
• Linoleic acid accumulates in fat tissue and "breaks" fat cells, causing metabolic dysfunction.
• The rise of seed oils in the 20th century correlates with the rise of heart disease, obesity, and chronic illness.

Paul Saladino, MD — one of the loudest voices on this — has called linoleic acid "the biggest driver of chronic disease" and has claimed it causes insulin resistance, DNA damage, and inflammation.^[1] RFK Jr., during his tenure as HHS Secretary, claimed Americans are being "unknowingly poisoned" by seed oils.^[2] The MAHA report from 2025 pointed to seed oils as potentially driving inflammation via omega-6 imbalance.

These claims aren't purely made up. There are real mechanisms being described. The problem is that mechanisms in a lab and outcomes in real humans often don't match up the way the narrative assumes.

So… Does It Actually Work?

Short answer: the inflammation hypothesis has not held up in human clinical trials.

When researchers have actually given people more linoleic acid — in controlled settings, measuring real inflammatory biomarkers — it doesn't consistently raise inflammation. In some cases, inflammatory markers go down. The cardiovascular outcomes data, which is the largest body of evidence, points in the opposite direction of what the seed oil critics predict: higher linoleic acid levels in the blood are associated with lower rates of heart disease, not higher.

That said, the story isn't all clean. Seed oils are rarely consumed in isolation. They travel with ultra-processed food. The omega-6 to omega-3 ratio question is real. And individual genetics — particularly variants in the FADS1 gene, which governs how your body converts linoleic acid — means people don't all respond the same way.

The Real Studies

Marklund et al., 2019 — Circulation (n=68,659)
This is the largest piece of evidence in the debate. A pooled analysis of 30 prospective cohort studies from 13 countries, following nearly 69,000 people across up to 32 years, looked at circulating linoleic acid levels and cardiovascular events. Result: higher linoleic acid in the blood was associated with a 22% lower risk of cardiovascular mortality and a 12% lower risk of ischemic stroke. Not a weak signal. The authors concluded that linoleic acid plays a favorable role in CVD prevention.^[3]

Fritsche, 2016 — systematic review of 15 RCTs
A review of 15 randomized controlled trials that directly tested the "linoleic acid causes inflammation" hypothesis found zero support for it. No significant impact on circulating CRP (a key inflammation marker). No effect on other inflammatory biomarkers.^[4] The review noted that all trials had relatively small sample sizes — the largest was 60 subjects — which is a real limitation.

Laurindo et al., 2025 — Frontiers in Nutrition (systematic review)
A systematic review of 11 clinical trials on seed oils in people with diabetes and dyslipidemia found that canola, flaxseed, and sesame oils generally improved lipid profiles and helped with glycemic control. Inflammatory markers were mixed — some studies showed reductions, others no change. No studies showed seed oils raising inflammation.^[5]

Soybean vs. palm oil RCT, 2025 — Current Developments in Nutrition
A double-masked crossover trial gave adults with overweight or obesity either 30g/day of soybean oil (high in linoleic acid) or palm oil for 4 weeks. After four weeks of eating the equivalent of about two tablespoons of soybean oil daily, most inflammatory markers were unchanged. Interleukin-6 actually showed a trend toward reduction in the soybean oil group. The researchers concluded that higher linoleic acid intake "is not proinflammatory as is stated in popular media outlets."^[6]

Kirkpatrick et al., 2024 — British Journal of Nutrition
A comprehensive perspective paper by seven researchers concluded that clinical trials consistently show increased n-6 PUFA (linoleic acid) intake does not increase markers of inflammation or oxidative stress. Evidence-based dietary guidelines support replacing saturated fat with unsaturated fat from plant sources.^[7]

Here's the Fine Print

A few caveats worth taking seriously:

Most trials are short and small. The Fritsche review noted that the largest RCT had just 60 completers. Long-term effects of high linoleic acid intake in free-living people are harder to test than a 4-week metabolic ward study. The observational data is huge, but observational data can't prove causation.

Genetics matter. FADS1 gene variants affect how efficiently people convert linoleic acid downstream. Some individuals produce more arachidonic acid — a precursor to some inflammatory compounds — from the same linoleic acid intake. The 2021 FADSDIET2 trial found that CRP responses to a high-linoleic acid diet differed significantly by FADS1 genotype.^[8] This doesn't mean seed oils cause inflammation for those people — but it means "seed oils are fine for everyone, full stop" might be an oversimplification too.

Seed oils come packaged with ultra-processed food. The real-world problem isn't usually someone drizzling canola oil on vegetables. It's that seed oils are ubiquitous in chips, fast food, packaged snacks. It's very hard to separate "seed oil" from "ultra-processed food" in most people's diets. The correlation critics point to — rising seed oil consumption alongside rising chronic disease — is also a correlation with rising ultra-processed food consumption generally.

Processing may matter. Cold-pressed vs. refined are genuinely different products. High-heat refining does create some oxidized byproducts. Whether those byproducts survive cooking in meaningful amounts and cause harm in humans at typical doses is still an open question. A 2025 federal toxicology report called residual hexane levels "toxicologically insignificant."

Who's Actually Going to Notice a Difference

Probably not the average healthy person swapping canola for butter. The data does not support a dramatic inflammation reduction from cutting seed oils specifically.

That said, there may be real value for people who:

• Eat a lot of ultra-processed food — cutting seed oils likely means cutting chips, fast food, frozen meals. The benefit there is real, but it's coming from the overall food quality shift, not just the oil.
• Have specific metabolic issues — some of the trial evidence for improved lipids and glycemic control comes from populations with diabetes or dyslipidemia.
• Are concerned about omega-6 to omega-3 ratio — the ratio argument isn't crazy. Increasing omega-3 intake (fatty fish, flaxseed) while moderating highly refined oils is a reasonable move with decent evidence behind it.

If you cook at home, use whole foods, and already eat reasonably well, switching from canola to avocado oil is unlikely to transform your inflammatory markers. It might make you feel better for other reasons. That's not nothing — but it's worth being honest about the mechanism.

Let's Kill Some Myths

"Linoleic acid directly causes inflammation." Not what the clinical trial evidence shows. Every major systematic review of RCTs finds no consistent increase in inflammatory biomarkers from higher linoleic acid intake.^[4]

"The 20th century heart disease epidemic proves seed oils are toxic." Correlation, not causation. The 20th century also saw massive increases in cigarette smoking, sedentary jobs, processed sugar, and changes in diagnostic accuracy. Extracting seed oils from those confounders as the cause isn't supported by the mechanistic or prospective data.

"Hexane in seed oil processing is poisoning you." Residual hexane in refined oils is regulated and measured. A 2025 federal toxicology review described the amounts as "toxicologically insignificant," and most remaining traces evaporate during cooking.^[2]

"Seed oils are a new industrial food with no history in human diets." Somewhat true, but the conclusion that "new = bad" doesn't follow from evidence. Lots of things are new. The question is what the data says about outcomes — and here, the data doesn't support harm in the quantities most people consume.

"Carnivore diet followers who eliminate seed oils feel dramatically better." Probably true for many people. But carnivore diets eliminate ultra-processed food, sugar, alcohol, and seed oils simultaneously. You can't credit the oil change alone.

If You Want to Try It

If You Want to Try It

If you want to reduce seed oil intake, here are cleaner alternatives:

• Avocado Oil on Amazon — High smoke point, mostly monounsaturated fat, solid everyday option. Look for 100% pure, cold-pressed.
• Browse on iHerb — Good selection of quality cooking oils.
• Fullscript — Professional-grade options.

Heads up: The Amazon link is an affiliate link — we earn a small cut if you buy through it, at no extra cost to you.

Verdict

Seed oils are not the poison their critics claim. The human clinical trial evidence — including a systematic review of 15 RCTs and large prospective cohort studies following tens of thousands of people — does not support the claim that linoleic acid from seed oils causes inflammation or cardiovascular disease. If anything, the epidemiological data points the other way.

But "not poison" doesn't mean "optimal." Cold-pressed, minimally processed oils like extra-virgin olive oil and avocado oil are reasonable upgrades. Cutting ultra-processed foods that happen to be loaded with refined seed oils is almost certainly a good move — just don't expect the oil to be the only thing doing the work.

The narrative is more interesting than the science. The science says: it's complicated, genetics matter, ultra-processed food context matters, and no, putting canola oil on your salad is not the reason you feel inflamed.

Quick Answers

Are seed oils bad for you?

The current evidence from human clinical trials does not support the claim that seed oils cause inflammation or cardiovascular disease. Large prospective studies actually associate higher linoleic acid levels with lower cardiovascular risk. "Not harmful" is probably the most evidence-backed position, though minimally processed alternatives like olive oil have their own independent benefits.

Why do people say seed oils cause inflammation?

The theory is that high omega-6 (linoleic acid) intake disrupts the omega-6 to omega-3 ratio, producing more pro-inflammatory compounds. This makes mechanistic sense at some level, but when tested in actual humans with actual inflammatory biomarkers, the effect consistently fails to appear. The inflammation hypothesis has not been supported in clinical trials.

Is canola oil actually bad for you?

No strong evidence shows canola oil is harmful at typical dietary amounts. It has a reasonable fatty acid profile with some omega-3 (ALA), and most studies show neutral to beneficial cardiovascular effects. The hexane-in-processing concern is real in theory but not supported as a meaningful risk at the residual amounts found in finished oils.

Should I switch to avocado oil or olive oil?

If you want to, go for it — both are good options. Extra-virgin olive oil has strong independent evidence for cardiovascular benefit. Avocado oil has a high smoke point and a favorable monounsaturated fat profile. But switching oils alone, without broader dietary changes, is unlikely to dramatically change your health markers.

What about the omega-6 to omega-3 ratio?

The ratio argument isn't nonsense. Most Western diets are skewed very high in omega-6 relative to omega-3. But the fix isn't necessarily to eliminate omega-6 — it's to increase omega-3 (fatty fish, flaxseed, walnuts) while reducing ultra-processed food intake broadly. Cutting canola oil while ignoring salmon probably won't move the needle much.

References

1. Saladino, P. (n.d.). Seed oils & processed foods: How they're harming you. Paul Saladino MD. https://www.paulsaladinomd.com/psmd-newsletters/seed-oils-processed-foods-how-theyre-harming-you
2. NPR. (2025, July 7). Are seed oils actually bad for your health? Here's what scientists say. https://www.npr.org/2025/07/07/nx-s1-5453769/nutrition-canola-rfk-seed-oils-soybean
3. Marklund, M., et al. (2019). Biomarkers of Dietary Omega-6 Fatty Acids and Incident Cardiovascular Disease and Mortality: An Individual-Level Pooled Analysis of 30 Cohort Studies. Circulation, 139(21), 2422–2436. https://pubmed.ncbi.nlm.nih.gov/30971107/
4. Fritsche, K. L. (2016). Linoleic acid, vegetable oils & inflammation. Missouri Medicine. PMC6179509. https://pmc.ncbi.nlm.nih.gov/articles/PMC6179509/
5. Laurindo, L. F., et al. (2025). Evaluating the effects of seed oils on lipid profile, inflammatory and oxidative markers, and glycemic control of diabetic and dyslipidemic patients: a systematic review of clinical studies. Frontiers in Nutrition, 12. https://pmc.ncbi.nlm.nih.gov/articles/PMC11849496/
6. Foods fortified with soybean or palm oil show no effect on inflammation or oxidized LDL in adults with overweight or obesity. (2025). Current Developments in Nutrition. DOI: 10.1016/j.cdnut.2025.107635. https://linkinghub.elsevier.com/retrieve/pii/S2475299125030975
7. Kirkpatrick, C. F., et al. (2024). Perspective on the health effects of unsaturated fatty acids and commonly consumed plant oils high in unsaturated fat. British Journal of Nutrition. DOI: 10.1017/S0007114524002459. https://pmc.ncbi.nlm.nih.gov/articles/PMC11600290/
8. Lankinen, M., et al. (2021). The FADS1 Genotype Modifies Metabolic Responses to the Linoleic Acid and Alpha-linolenic Acid Containing Plant Oils — Genotype Based Randomized Trial FADSDIET2. Molecular Nutrition & Food Research, 65(5). DOI: 10.1002/mnfr.202001004. https://onlinelibrary.wiley.com/doi/10.1002/mnfr.202001004

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