Are Seed Oils Bad For You? What the Evidence Actually Shows in 2026
Sunflower oil is the cooking oil in more British kitchen cupboards than any other, and for the best part of a year a good chunk of the internet has been telling you it’s quietly wrecking your heart. Search “are seed oils bad for you” and you’ll find wellness influencers calling rapeseed oil “liquid inflammation,” TikTok videos urging you to switch to beef tallow for your chips, and at least one podcast bro comparing a bottle of vegetable oil to a bottle of poison. It’s a tidy story. It’s also mostly wrong, and the bit that isn’t wrong gets stretched a long way past what the evidence supports.
In This Article
- So, are seed oils bad for you? Start with what they actually are
- Where the panic started
- The one study the sceptics actually have
- What the bulk of the evidence shows
- The oil was never really the problem
- Heat matters more than the bottle
- Who genuinely needs to moderate their intake
- What I'd do in my own kitchen
I’ve spent the past fortnight reading through what’s actually been published on linoleic acid, omega-6 fats and heart disease, rather than what’s been clipped into a 45-second reel. The honest answer is more interesting than either camp wants it to be, and it doesn’t fit neatly on a slide with a red cross through a bottle of Flora.
It also isn’t a small question. Sunflower and rapeseed oil turn up somewhere in most of what a typical British household eats in a week: the pan a Sunday roast goes in, the fryer behind the counter at the local chippy, half the tubs and packets on a supermarket middle aisle. If they really were doing the damage the loudest voices claim, that would be one of the bigger public health stories going. If they’re not, a lot of people are currently binning a perfectly good bottle of oil for nothing.
So, are seed oils bad for you? Start with what they actually are
“Seed oil” isn’t a scientific category, it’s a marketing one, coined by critics rather than the food industry. It generally covers rapeseed (canola), sunflower, corn, soybean, grapeseed and sesame oils: fats extracted from the seeds of plants rather than pressed from fruit like olives, or rendered from animal fat like lard and tallow. In a British kitchen, that mostly means rapeseed and sunflower oil, the two most commonly sold in supermarkets.
The case against them, as made online, usually rests on one nutrient: linoleic acid, an omega-6 polyunsaturated fat that makes up a large share of these oils. The claim is that modern diets are drowning in omega-6, that this drives chronic inflammation, and that inflammation drives more or less every disease you can name. It’s a claim with just enough biochemistry in it to sound credible to someone without a nutrition science background. And it’s the claim worth actually testing.
Where the panic started
This isn’t really a British story to begin with. It’s an American one that crossed the Atlantic on TikTok. US health secretary Robert F. Kennedy Jr and the Make America Healthy Again movement made seed oils a central villain of their food agenda through 2025, folding them into a wider narrative about ultra-processed food, chronic disease and industrial agriculture. Some of that wider narrative has genuine substance. The seed oil claim in particular has been picked apart repeatedly by nutrition scientists, who point out that it rests on cherry-picked animal studies and a handful of old, poorly designed human trials. Farmers growing canola and soybean in the US have complained publicly about the economic hit as the panic spread, which tells you something about how far it travelled beyond a niche wellness forum.
By the time it reached UK wellness accounts, the argument had lost most of its caveats and gained a lot of confidence. “Seed oils are toxic” travels better than “there’s one 1960s trial with a complicated story and a lot of context missing,” and a punchy claim with a villain in it will always outrun a careful one. It doesn’t help that the people making the loudest claims are often also selling the tallow, the ghee or the supplement stack positioned as the alternative.
The one study the sceptics actually have
Give the seed oil sceptics their due: there’s a real study behind this, not just vibes. In 2013 a team led by Christopher Ramsden dug up and reanalysed the original data from the Sydney Diet Heart Study, a trial run between 1966 and 1973 on 458 Australian men recovering from a coronary event. One group was told to swap saturated fat for safflower oil, rich in linoleic acid, while the control group got no specific dietary advice. Published in the BMJ, the reanalysis found the safflower oil group had a higher rate of death from all causes, and from coronary heart disease in particular, than the control group did.
That’s a genuinely uncomfortable result, and it’s the study seed oil critics quote most often. What they tend to leave out: it’s a single 50-year-old trial of 458 men, using margarines that would also have contained industrial trans fats we now know are harmful, with no attempt to also raise omega-3 intake alongside the omega-6. Recovering 45-year-old paperwork and rerunning the numbers is a genuinely useful piece of scientific archaeology. It doesn’t automatically make the result generalisable to a 2026 kitchen stocked with fresh rapeseed oil and a diet that looks nothing like a 1960s hospital canteen’s. One study from that era, with that many confounding variables, isn’t nothing. It also isn’t the whole picture, and treating it as the final word means ignoring almost everything published since.
What the bulk of the evidence shows
Line up the newer, larger and better-designed research and the picture flips. HEART UK, the cholesterol charity, points to an analysis of 30 studies tracking blood fat levels in thousands of people for up to 32 years: those with higher linoleic acid levels in their blood actually had a lower risk of cardiovascular disease, not a higher one. A 2020 Cochrane review of 15 controlled trials involving more than 56,000 people found that replacing saturated fat with unsaturated fat, including the polyunsaturated fat in seed oils, cut cardiovascular events by 21%.
On the inflammation claim in particular, HEART UK cites a review of 36 human studies in which even dramatic swings in linoleic acid intake, up by over 500% or down by 90%, didn’t shift blood levels of arachidonic acid, the compound the “seed oils cause inflammation” theory depends on. A separate review of 15 randomised controlled trials found next to no evidence that adding linoleic acid to a healthy adult’s diet raises inflammatory markers at all.
None of that is a secret held by dieticians and hidden from the public. It’s on a UK charity’s website, written for anyone to read.
The oil was never really the problem
Here’s my honestly held, slightly unfashionable opinion after reading all this: the anti-seed-oil movement is solving the wrong problem. If you eat a lot of ultra-processed food, you are eating a lot of seed oil, because it’s cheap and stable and everywhere in that category, from biscuits to ready meals to the fryer at the chip shop. But the thing making that food a poor choice is the whole package, not the oil in it on its own. Swap the seed oil for beef tallow in a packet of crisps and you haven’t made a health food. You’ve just changed which fat is doing the damage, and probably increased the saturated fat load while you’re at it.
That matters because tallow, the trendy replacement, is roughly 50% saturated fat. Coconut oil, the other fashionable swap, is around 87% saturated fat. The British Heart Foundation puts rapeseed oil at just 7% saturated fat and sunflower oil at 12%, against butter’s 52%. If your actual goal is a lower cardiovascular risk, and for most people concerned about heart disease it should be, switching from rapeseed to tallow is a step in the wrong direction dressed up as a step forward. We covered a similar dynamic with beef tallow’s rise as a skincare ingredient: the “it’s traditional, so it must be better” instinct keeps outrunning the actual chemistry.
And no, this isn’t me saying everything about the anti-seed-oil crowd is nonsense. They’re right that the average UK diet leans far too heavily on omega-6 relative to omega-3, and the NHS itself notes most of us already get plenty of omega-6 without trying. That imbalance is worth correcting. It’s just better corrected by eating more oily fish, as we’ve written about in the context of fish oil supplements and where they actually help, than by fearing a bottle of rapeseed oil sitting next to your hob.
Heat matters more than the bottle
If you want one genuinely useful, evidence-backed thing to take from all this, it isn’t which oil to buy. It’s how you treat it once it’s in the pan. Every cooking oil has a smoke point, the temperature at which it stops frying your food and starts breaking down into compounds you don’t want to eat, and that point varies a fair bit. Refined rapeseed oil copes well with a hot wok or a roasting tray, somewhere around 200°C. Extra virgin olive oil, prized for its flavour, starts to degrade at a noticeably lower temperature, which is exactly why chefs use it for dressings and finishing rather than for searing a steak. Butter burns lower still.
None of that is about seed oils being uniquely dangerous. It’s just basic kitchen chemistry that gets lost when the conversation is “this oil bad, that fat good” rather than “use the right fat for what you’re actually cooking.” A cheap bottle of rapeseed oil used fresh, at a sensible heat, for a Tuesday night stir-fry is doing you no harm at all. The same bottle, reused for the fourth time in a deep fat fryer that’s been sitting at a high temperature all afternoon, is a different story, and that story has nothing to do with the seed it came from.
Who genuinely needs to moderate their intake
There’s a narrower, more defensible version of the seed oil concern, and it’s worth separating from the noisy one. If you deep-fry regularly using the same oil over and over, reheating it past the point it starts to break down, you’re creating genuinely harmful oxidation products, whatever type of oil you started with. That’s a real risk, and it applies more to commercial fryers reusing oil for days, or to anyone who tops up the same bottle at home for weeks rather than replacing it, than to a home cook using a fresh bottle of rapeseed for a stir-fry twice a week.
People eating very little oily fish alongside a diet unusually heavy in fried and processed food are the group where the omega-6 to omega-3 ratio genuinely gets skewed enough to matter. If that’s you, the fix isn’t switching your cooking oil. It’s eating more mackerel, salmon or sardines, or cutting back on the fried and packaged stuff generally, two changes that do far more for your actual risk than any amount of tallow shopping.
Everyone else, cooking at home with rapeseed or sunflower oil a few times a week as part of an otherwise reasonable diet, doesn’t have much to worry about here. That’s most people reading this.
What I’d do in my own kitchen
I haven’t thrown out my rapeseed oil, and I’m not going to. It’s about a third of the price of olive oil, has a higher smoke point, and does exactly what I need it to do on a weeknight. But I have started buying oily fish more often than I used to, which is a genuinely boring piece of advice compared to “seed oils are poisoning you,” and boring advice rarely goes viral. It doesn’t need to. It’s just correct.
I’ll admit the tallow trend has a certain romance to it, all cast iron and “the way your grandmother cooked.” My gran, for what it’s worth, cooked with lard, suet and whatever dripping was left in the tin, and she also died of the heart disease that a diet heavy in saturated fat makes more likely. Nostalgia isn’t evidence, however good it looks on camera.
What’s actually changed, reading through the marketing versus the trial data side by side, is how sceptical I’ve become of any wellness claim built on a single dramatic statistic with no source attached. The greens powder industry runs on the same trick, as does a lot of the longevity supplement market: take a real, narrow finding and stretch it into a sweeping health claim that sells better than the boring truth. We found exactly that pattern digging into greens powders and again with NMN supplements. Seed oils just happen to be the fear-based version of the same playbook, rather than the hope-based one.
So the next time a bottle of vegetable oil gets called toxic on your feed, it’s worth asking what the person posting is actually selling instead, and whether they’d still have an audience if the answer was just: cook with what you’ve got, eat more fish, and worry less about your cupboard.
What’s the wellness claim that’s had you second-guessing something in your own kitchen this year?
