What Are Seed Oils? (And Are They Really As Bad As TikTok Says?)

I’m not certain when exactly I decided to re-examine my relationship with seed oils. Perhaps it was when a bottle of olive oil—the standard stuff, mind you—started to hit the $15 mark, while a bottle of rapeseed oil only costs $3. Or, perhaps it was when I realized that one of the loudest and most unrelenting voices lambasting seed oils was Robert F Kennedy Jr (aka RFK Jr), a known and prolific vaccine sceptic. Most likely, it was when I read the recent large and comprehensive study about plant oils (which include seed oils) published in The Journal of the American Medical Association last month. The report linked plant oils with lower total cancer and cardiovascular disease mortality—a distinct departure from the fearmongering happening online.

What are seed oils?

A quick search of “seed oils” on TikTok and the noise rages louder. There’s one video titled “toxic seed oils that can k*ll you,” and another claiming that seed oils are “ the worst thing you can consume” set to ominous backing music. The purported villains? Oils dubbed the “hateful eight”: rapeseed oil (known as “canola” in America), sunflower oil, soybean oil, cottonseed oil, corn oil, grapeseed oil, rice bran oil, and safflower oil.

Are seed oils actually bad for you?

It’s the process used to extract the oil from the plants and seeds that makes them so toxic, according to detractors. Because of the methods used, they are claimed to promote inflammation in the body and are more prone to oxidation (which degrades the quality and can produce harmful compounds). Added to this, critics link the increased consumption of these oils in recent decades to the rise of cardiovascular disease, type 2 diabetes, and cancer—often represented in colourful, frightening infographics on social media.

“The thing is,” Dr Sarah Berry, chief scientist at Zoe and professor of nutritional sciences at King’s College London, cautions, “these graphics show association. Association doesn’t mean causality. Hundreds of other things have changed in that time, and our food landscape has changed almost beyond recognition. We estimate that around 60% of our seed oil intake comes from heavily processed foods, which we know contain many other unhealthy ingredients and are lacking in fiber, etc, too. So, this is where we have to disentangle what’s due to seed oils versus what’s due to the fact that seed oil intake is associated with the intake of some really unhealthy foods.”

In simple terms, if you’re consuming fried chicken and chips every day—which happen to contain or be cooked in seed oil—it’s probably not the oil itself that’s causing your health, weight, or mood issues. Nevertheless, RFK Jr has said we are being “unknowingly poisoned” by seed oils and advocated for a switch to beef tallow in the American fast food industry. He’s even sold hats with the snappy slogan “make frying oil tallow again” (MFOTA?) on his campaign website, prior to being made US health secretary.

In fact, the JAMA study, which Berry points out was a large-scale meta-analysis of multiple different groups of people over many years, found that “substituting butter with plant-based oils, particularly olive, soybean, and canola oils, may confer substantial benefits for preventing premature deaths.” Yes, seed oils are more prone to oxidation (and, therefore, degradation and loss of nutritional value) than beef tallow or butter, says Berry. “But unless you’re heating the oil at excessive temperatures repeatedly over multiple days and leaving it out, I don’t believe there’s any real negative impact on health.”

Is there a “best” way to extract oil?

The one anti-seed oil claim that did give me pause was that the many processes that refined seed oils go through—in terms of extraction, bleaching, and deodorizing—remove their health benefits and make them harmful. Obviously, this doesn’t apply to all seed oils (cold-pressed seed oils are what is produced when seeds are squeezed to extract their oil), but is there such a thing as a “good” seed oil and a “bad” one?

“I am not aware of any published research that shows head-to-head comparisons in a randomized control trial in humans on cold-pressed versus refined oils,” Berry tells me. “I’d love that research to take place, but nearly all of the trials that have been carried out on seed oils used refined oils and still show the health benefits.” Berry does share, though, that processing and refinement can cause the removal of some phytonutrients and polyphenols, but that many of the antioxidant compounds are found in similar amounts whether it’s refined or cold-pressed. “Not all processed things are bad for us – the refinement process ensures the oil is safe and won’t go rancid so quickly.”

Sensing my hesitation, I think, Berry adds the clincher that on her own shopping list, it’s refined seed oil all the way. “I can afford cold-pressed, but I buy the commercial, refined seed oils for myself,” she says. “I find the cold-pressed oils very expensive, and there is no current evidence to show they’re more beneficial than refined seed oil.”

Could the fatty acids in seed oils be detrimental to our health?

Then, there are the specific fatty acids found in plant oils. Seed oils are high in omega 6, something critics have linked to inflammation, though a 2019 Harvard report dismissed this—while extra virgin olive oil, for example, is higher in omega 3. Both are crucial for our health (there’s a reason they’re known as “essential fatty acids”), with the former lowering harmful LDL cholesterol and keeping blood sugar in check, whilst the latter is packed full of polyphenols, protects the heart, eases inflammation and inhibits the formation of dangerous clots in the bloodstream.

In terms of optimising your balance of good fats, Hannah Alderson, a BANT-registered nutritionist and author of Everything I Know About Hormones, says it’s all about ensuring your omega 3 intake remains high, in the face of increased intake of seed oils in commercial cooking, and a subsequent “underconsumption of omega-3-rich foods” by the general population. But it’s not all about oil.

“Increase foods high in omega 3,” she affirms. “You can do this by eating grass-fed meats, algae, walnuts, flaxseeds, chia seeds, and oily fish,” she explains. And if you still have your reservations, “try picking a cold-pressed product over a chemically extracted oil.”

I’ll also be following Alderson’s best practice oil advice, reducing exposure to light, plastic, oxygen, and heat, which she says can promote damage. “Buy oil in glass bottles, especially dark glass, and store it in a dark, cool cupboard,” she recommends. “Use a tight-fitting lid on the bottle, and don’t pour oil directly into a hot pan—let it warm up.”

A final word on seed oils

As is often the case with health and diet, expert advice is dull compared to the horror stories conveyed on TikTok. We aren’t being fed poison and there are no magic bullets. It seems that, as I suspected, we just need to eat a variety of foods in a responsible and balanced way.

Extra virgin olive oil has always been my go-to, partly because I have two small children and so we live a pasta-based lifestyle, and partly because of a snobbish preference for oils presented in green glass bottles with fancy matte labels and swirly text. Berry says that’s great, though, due to EVOO’s consistently proven benefits for heart health and more. But it’s also expensive and has a strong taste which isn’t always suited to other dishes like stir-fries and curries, for example.

Now, though, I’ll feel more confident opting for a more neutral-tasting oil like rapeseed, and the same goes for oil-based baking, which has begun to feel like a pretty indulgent pursuit when using olive oil. And then, of course, there’s butter, which I’ll continue to slather onto toast after discussing it in depth with Berry. “The evidence is really clear that butter increases total cholesterol and cardiovascular risk compared to olive oil and seed oil, but at the end of the day we have got to enjoy our food. A little bit of butter each day isn’t going to harm you.”

And thank goodness for that.