The truth about cooking oils and which are best

Whether you use oil for deep frying, sautéing, roasting or salad dressings, choosing the right one can be complicated.

It's not just health you might be thinking about, but price, flavour and environmental impact, too.

Here's everything you need to know.

Oils can be refined or unrefined – although some bottles will be a blend of both.

If you spot 'virgin', 'extra-virgin' or 'cold-pressed' on the bottle, chances are it's unrefined and has hung on to most of its nutrients.

Refined oils have been processed and treated with chemicals to extend their shelf life and remove unwanted flavours and odours. In the process, some of the healthy compounds are lost, but they generally tolerate heat better than unrefined oils.

When we say 'tolerate heat', what we're talking about is an oil's smoke point – the temperature which it starts to burn and degrade.

When oils are heated, especially at high temperatures, or reused repeatedly, they can break down and form potentially harmful compounds, external called aldehydes.

That's why Prof Martin Grootveld, external, a bioanalytical chemist, suggests limiting the number of times you re-use frying oils, especially refined corn, groundnut (peanut) or sunflower oils, to once or twice.

Olive oil is key to the Mediterranean diet. And, as well as tasting delicious, it's high in monounsaturated fat (which has several health benefits) and is associated with lower risk of heart disease and other chronic illnesses, according to studies, external.

Olive oil that is a blend of refined and unrefined is a safe bet for cooking with. That way, you keep more of the health benefits and flavours that are lost in refinement, while there's less concern about low smoke points.

But if you have an unrefined olive oil (like extra virgin, for instance) you're best off saving it for drizzling over dishes or whisking into vinaigrettes. Essentially, use it as a condiment.

Lots of seed oils are lumped in the same category and seen as having high levels of polyunsaturates. But rapeseed oil is different.

It's extracted from the yellow-flowering rape plant, which is widely grown in the UK.

Given we have such a good supply, the generic 'vegetable oil' you'll see on UK supermarket shelves is usually refined rapeseed oil.

But its locality and abundance (and therefore often more wallet-friendly price) aren't this oil's only virtues.

"Rapeseed oil is an unsaturated fat and high in monounsaturated fat, making it a healthier type of oil than some others," says Victoria Taylor, senior dietitian at the British Heart Foundation.

It's also rich in vitamin E and omega 3, 6 and 9 fats, which support brain, heart, and joint function, external. And let's not forget its delicate nutty flavour which makes it great for cooking.

That said, Grootveld advises heating it at low temperatures and using "as little as possible if you're roasting, shallow frying or sautéing things like vegetables".

That's because it does still contain some polyunsaturates and is still high in calories, external.

If you're buying cold pressed (which is almost certainly going to be unrefined) it will cost more than the bottles of refined veg oil, but, it's also likely to be cheaper than unrefined olive oil.

You can get saturated fats from both plant and animal sources, like red palm oil, lard and beef dripping. They create fewer aldehydes.

While saturated fat has long been linked to high cholesterol, external (the NHS recommends limiting your intake of it), the relationship between saturated fat and heart health is complex and advice is evolving, external.

Coconut oil is extremely high in saturated fat (significantly more than butter) and the refined version is the best to cook with, Grootveld says.

Still, Taylor recommends using it sparingly.

"If you like the taste of coconut oil, then, as with butter, it's fine to use every now and then. But be careful not to overdo it and use unsaturated oils as an everyday choice instead."

Palm oil probably has the poorest environmental credentials – it's production causes deforestation.

Sunflower and rapeseed oils made outside Europe and the UK are widely sprayed with neonicotinoids, external, which are implicated in killing bees, butterflies and other pollinating insects, and are now largely banned in Europe and the UK., external

Avocado, external, soy and almond oils might not be the greenest choice either, depending on how they're sourced. They're also linked to deforestation and insecticide use, as well as other detrimental farming practices.

Alex Crumbie from the not-for-profit Ethical Consumer says, if budget allows, opt for organic and buy oil in glass bottles, rather than plastic.

And don't throw used cooking oil down the sink, as it can cause fatbergs. Small amounts can be added to your food waste bin or disposed of in a sealed container in your general waste bin.

Originally published April 2022. Updated February 2026.

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