Are seed oils bad for you?

Seed oils have been stirring up a storm lately, with countless influencers weighing in on their supposed dangers on social media. Here are the facts.

Visit any social media site and search for #seedoils. You’ll find they’ve become a hot topic.

While they’ve traditionally been seen as a healthier option than animal-based saturated fats such as butter or lard, now some influencers are saying that they come with health risks. So, what’s the truth?

What are seed oils?

“The term ‘seed oils’ refers to oils extracted from the seeds of plants, such as sunflower, rapeseed (canola), soybean and grapeseed,” explains dietitian and author of ‘How Not to Eat Ultra-Processed’, Nichola Ludlam-Raine.

“While many plant-based oils do come from seeds, others like olive oil and avocado oil are made from the fruit flesh instead. The key difference is in the fatty acid profile and the way the oils are processed.”

In the UK, the seed oils we consume most of are sunflower oil and rapeseed oil, says University of Reading’s Prof Parveen Yaqoob OBE. The latter is what’s most commonly used in the products sold as vegetable oil.

Yaqoob explains that sunflower oil is polyunsaturated and rapeseed (vegetable) oil is monounsaturated. This means that sunflower oil tends to be higher in omega-6, while rapeseed oil is more balanced with both omega-6 and omega-3 oils.

Why are people against seed oils?

“Some concerns stem from the fact that some seed oils are high in omega-6 polyunsaturated fats, which, when consumed in large amounts without enough omega-3s, may contribute to inflammation,” explains BDA spokesperson Ludlam-Raine.

The idea is that the inflammation could be damaging to cardiovascular health, with some influencers saying that a diet high in seed oils can increase the risk of heart disease and strokes. But Dr Louise Flanagan, head of research at the Stroke Association, says there isn’t evidence to back this up.

“While there is a lot of talk about seed oils being bad for health, scientific evidence does not this. In fact, there’s generally not a lot of research looking at the benefits or drawbacks of specific plant oils.

“The most recent research, published in March 2025, studied the diet and health of over 200,000 people in the USA over around 30 years.

“The researchers looked at the relationship between how much butter and plant oil (which included various seed oils as well as olive oil) a person consumed and their likelihood of dying of cardiovascular disease (CVD), including stroke or cancer.

“The results showed that higher plant oil consumption is associated with a lower risk of death caused by CVD.

“Higher intakes of plant-based oils (whether made from seeds or flesh) were associated with lower risk of total mortality, or mortality due to cancer and cardiovascular disease.

“The researchers didn’t directly test what happens if someone switches from butter to plant oils, but they were able to calculate the likely effects. They found that switching to plant oils is likely to reduce your risk of death from any cause and reduce your risk of death from cancer, but the evidence was less clear on reducing your risk of death from CVD.”

Ludlam-Raine adds: “Population studies haven’t shown harm from seed oils – ultimately when you replace saturated fat (butter, for example) with unsaturated fat (such as seed oils), you get better health outcomes.”

Does seed oil’s processing cause health issues?

“When you make seed oils, you need some sort of chemical extraction process,” explains Yaqoob.

“Because of the focus on ultra-processed foods and the linked negative health outcomes, some people think that using a process to get the oil out of the seeds makes it bad. I don’t necessarily think that’s the case.”

There’s little evidence to say the processing could cause issues.

Newcastle University’s Dr Paul Bilsborrow, says, “Most [seed oils] are processed via hexane extraction with bleaching to remove colour and additives.”

While there is some evidence to suggest hexane could be linked to several health conditions, the oil goes through processes to ensure the hexane is removed.

“There is also the option of cold pressing,” points out Bilsborrow. “In fact, cold-pressed rapeseed oil has a better health profile than chemically extracted rapeseed – but it does cost more.”

Are seed oils dangerous when heated?

“Another worry is the formation of harmful compounds when oils are heated at high temperatures, but this mostly applies to repeated high-heat frying, not home cooking,” says Ludlam-Raine.

An example of this would be if a fast-food retailer used the same batch of cooking oil repeatedly.

Yaqoob agrees. “I think that’s actually the key risk with oils, that if you reheat them many times they do oxidise and that’s not good for you.

“If you’ve got oxidised molecules in your body, they can cause inflammation and they can cause the cells in your arteries to behave in a way that’s not necessarily good. They basically become ever so slightly toxic.”

“I shudder when I think about the amount of times my mother used to reheat oil to fry samosas in when I was growing up. And you can taste it, you get this rancid flavour that’s the oxidisation of the fatty acids.

“But that’s not about the composition of the oil – it’s about what you do with it.”

Is seed oil the problem or the food we’re using it in?

Bilsborrow says, “If you’re buying vegetable oil, then there’s no real health concerns. But as a component of heavily processed foods it should be avoided.”

Some of the rhetoric surrounding seed oils and the risks they pose focuses on how, since they have become more commonplace, there has been an increase in health issues. However, what’s important to is that ultra-processed foods (UPFs) have also become substantially more popular during the same time. Many UPFs contain lots of oil and are unlikely to be healthy.

“And it’s mainly seed oils that are present in HFSS (high in fat, sugar and salt) ultra-processed foods,” says Ludlam-Raine.

Should I avoid seed oils?

The experts above agree that seed oils, in moderation, are fine and in fact can come with some health benefits.

For instance, Flanagan says, “To help reduce your risk of stroke, we recommend that people are mindful of the amount of saturated fats in their diet, found in products including butter, palm oil and coconut oil. We encourage people to try to eat more unsaturated fats instead, found in most plant oils, nuts, seeds and fish.”

“There’s no need to completely avoid seed oils. In fact, many are rich in vitamin E and unsaturated fats,” adds Ludlam-Raine. “That said, consuming a variety of fats, including olive oil, nuts, seeds and oily fish (for beneficial omega-3 fatty acids), is best for overall health.

“I personally use both rapeseed oil and olive oil at home in cooking and in salad dressings – choose extra virgin or cold-pressed if you can for more nutrients.

“Look beyond the hype. A small amount of cold-pressed or minimally refined seed oils used in cooking or dressings is perfectly fine as part of a balanced diet.

“Try to focus more on your overall dietary pattern, aiming for one that is rich in vegetables, wholegrains, lean proteins and healthy fats, rather than obsessing over individual ingredients.”

Originally published May 2025

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