The healthiest oils to cook with and the ones to avoid

29/06/2024

The answer as to which oil is best to cook with is complicated

Oil is the ultimate kitchen staple, used for everything from sautéing and deep frying to roasting and pouring into salad dressings. Extra virgin olive oil is renowned for its health benefits – but is it the right choice for every culinary task? The answer is complicated.

When you’re frying or heating oil to a high temperature (usually around 180C), it breaks down in a process known as oxidation. Fat molecules react with oxygen in the air to form substances called aldehydes and epoxides, types of lipid oxidation products (LOPs). Both are toxic and can be transferred to food.

‘‘LOPs have been linked to a range of health concerns including cancer, heart disease, birth defects, raised blood pressure and inflammation,’’ says Prof Martin Grootveld, a bioanalytical chemist at De Montfort University who has studied cooking oils for 30 years.

The hotter the oil gets, the more of these chemicals are produced, especially at the ‘smoke point’ – the moment at which it starts to burn and smoke.

What many people don’t realise is that unsafe levels of toxins are also generated below the smoke point, too. The risk of this happening is measured by the peroxidative susceptibility index (PSI); the higher the PSI, the more readily it degrades. Some oils oxidise and go rancid at room temperature, which is why it’s important to pay attention to the best before date on the bottle.

So, how do you know which oil is best for the job? We asked the experts. Note: the health score reflects an oil’s healthiness when used for cooking.

Extra virgin olive oil

A cornerstone of the Mediterranean diet, these unrefined oils are rich in healthy monounsaturated fats (MUFAs) and an array of beneficial plant compounds. “They haven’t been exposed to excessive heat, so healthy compounds like antioxidants and sterols, which are known to reduce cholesterol, have been retained,” Prof Grootveld says.

These oils are fine for frying, sautéing, roasting and baking, Prof Grootveld says, but he believes refined olive oils are better because they produce fewer toxic compounds when heated (see below).

Also, to reap the full health benefits of extra virgin olive oil, which are generally much more expensive, they’re best used unheated. “Once you start blasting them with heat, some of those healthy molecules are destroyed.”

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Tracy Parker, senior dietitian at the British Heart Foundation, agrees. “Extra virgin oils are best left as finishing oils to maintain their flavour and aroma,” she says.

Calories per tablespoon: 119

Typical smoke point: 175-210C

Suitable for: Fine for all types of cooking with heat but fewer toxic compounds are created with regular olive out and some of the healthy compounds will be destroyed. Ideal for dressings and pouring over finished dishes, but the flavour may not be suitable for south-east Asian dishes.

Healthiness: Abundant in MUFAs which are good for heart health, anti-inflammatory and antioxidant compounds. Make this your go-to oil.

Health score:

Recommended: 245 Organic Extra Virgin Olive Oil

Virgin olive oil

Virgin olive oil is produced with more heat than extra virgin olive oil, so some of its healthy compounds have been destroyed. Olive oil is a blend of refined olive oil (processed and treated with chemicals to extend shelf life and remove unwanted flavours and odours) and virgin olive oil, which is added for colour and flavour.

“Large amounts of healthy antioxidant and sterol molecules have been removed, especially from refined olive oils,” Prof Grootveld says. “But they generally tolerate heat better than unrefined oils and have a higher smoke point.”

He recommends refined olive oil – generally labelled ‘olive oil’ – for frying, as it’s less likely to degrade than extra virgin olive oil. Parker suggests reserving these oils for baking, sautéing and sauces, which involve lower temperatures than high-heat frying and searing.

Calories per tablespoon: 119

Smoke point: 200-250C

Suitable for: All types of cooking with heat. Olive oil has little flavour, so it’s not ideal for dressings.

Healthiness: These oils don’t contain the same level of beneficial compounds as extra virgin olive oil but are still a source of heart-healthy MUFAs.

Health score:

Recommended: La Espanola Olive Oil

Sunflower oil

We generally think of sunflower oil as healthy because it’s low in saturated fats and rich in healthy polyunsaturated fats (PUFAs), which can help lower ‘bad’ cholesterol, and vitamin E. This is true at room temperature, but not when subjected to the heat of frying.

Sunflower oil has a high smoke point, but also a high PSI, so it degrades easily. “I wouldn’t recommend any oil rich in PUFAs for shallow frying,” Prof Grootveld says. Why? Shallow frying generates more toxic compounds than deep frying, because a larger surface area of oil is exposed to oxygen in the air.

Calories per tablespoon: 120

Typical smoke point: 246C

Suitable for: Generally acceptable for deep frying if the temperature is as low as possible, but not shallow frying. Never re-use the oil, as toxic compounds build up. Best for dressings.

Healthiness: Low in saturated fat, high in healthy PUFAs including omega-3, and vitamin E.

Health score:

Recommended: Mountain Produce Cold Pressed Sunflower Oil

Rapeseed oil

Rapeseed oil contains virtually no saturated fats and is high in healthy MUFAs, as well as beneficial plant compounds (although this varies depending on how it was harvested, stored and processed). It’s also rich in vitamin E, as well as omega-3, 6 and 9 fats, which support brain, heart, and joint function.

Rapeseed oil doesn’t degrade as easily as PUFA-rich sunflower oil. However, Prof Grootveld still advises against rapeseed oil for shallow frying. “It’s fine for deep frying but as with sunflower oil, don’t use the same batch more than once,” he says.

Like olive oil, rapeseed oil is available refined and unrefined. In the UK, oil labelled ‘vegetable oil’ is usually refined rapeseed oil and has almost no flavour. Unrefined rapeseed oils are often labelled ‘cold-pressed’, ‘premium’, ‘virgin’ or ‘extra virgin’, and have a more pronounced, sometimes nutty flavour.

Calories per tablespoon: 124

Typical smoke point: 205-230C

Suitable for: Deep frying (but never re-use the oil), sautéing, grilling and baking. Use cold-pressed and virgin versions for dressings.

Healthiness: Very low in saturated fat, high in healthy mono-unsaturated fat which can help reduce cholesterol levels. Also contains essential polyunsaturated omega-6 and omega-3 fatty acids.

Health score:

Recommended: Ramsbury Black Gold Rapeseed Oil

Groundnut (peanut) oil

Groundnut oil is refined peanut oil with little or no peanut flavour. It’s high in MUFAs but also contains PUFAs. “It’s susceptibility to generate toxic compounds when heated falls between sunflower and olive oil,” Prof Grootveld says. “It will be OK for deep frying once or twice, but only once for careful, low-temperature shallow frying, without reuse.”

“Peanut oil contains quite high levels of omega-6 but no omega-3 which can be pro-inflammatory,” adds nutritionist Sam Rice. Why? For optimum health, we need to consume these types of fats in a healthy ratio. But omega-6 is largely found in vegetable oils like groundnut, which are abundant in ultra-processed foods. These now make up almost 60 per cent of the British diet, so many of us consume too much omega-6 compared to our intake of omega-3.

Calories per tablespoon: 119

Smoke point: 230C (refined)

Suitable for: Deep frying once or twice and shallow-frying at low temperatures.

Healthiness: High in heart-healthy MUFAs that can help lower ‘bad’ cholesterol, and a good source of vitamin E. But may contribute to an imbalanced intake of omega-3 and omega-6.

Health score:

Recommended: Waitrose Groundnut Oil

Coconut oil

Coconut oil is extremely high in saturated fat (significantly more than butter) and can be used for all types of frying, Prof Grootveld says. “It’s virtually resistant to oxidation,” he adds.

The flip side is that saturated fat is the kind we’re advised to limit our intake of, as saturated fat can raise blood cholesterol levels, which is associated with an increased risk for heart disease, they are recommended to be consumed in small amounts.

Raw virgin coconut oil is cold-pressed from the flesh of organic coconuts and contains higher levels of antioxidants and other healthy plant compounds. However, Prof Grootveld says the refined version is better for cooking at high temperatures because its smoke point is considerably higher than unrefined.

Calories per tablespoon: 117

Typical smoke point: 177C refined/204C unrefined

Suitable for: All types of frying

Healthiness: Almost entirely composed of saturated fats, the kind we are advised to limit our intake of, as it can raise your LDL (bad) cholesterol and your chances of cardiovascular disease and stroke. However, it’s one of the best oils to cook with if consumed occasionally in small amounts.

Health score:

Recommended: Biona Organic Raw Virgin Coconut Oil

Sesame oil

Widely used in southeast Asian cooking, sesame oil is made from pressed sesame seeds. The refined version – generally just labelled ‘sesame oil’ – has a higher smoke point than unrefined and is neutral tasting.

The unrefined version – generally labelled ‘toasted sesame oil’ – has a lower smoke point and an intensely nutty flavour.

Sesame oil is rich in MUFAs but also PUFAs, which means it’s susceptible to oxidation, so not recommended for shallow-frying. “It’s suitable for deep frying only, and only use the oil once,” Prof Grootveld says. He recommends reserving unrefined sesame oil for drizzling over cooked dishes.

Calories per tablespoon: 120

Typical smoke point: 177C unrefined/232C refined

Suitable for: Deep frying (but never re-use the oil). Use cold-pressed and virgin versions for dressings.

Healthiness: Rich in unsaturated fats and antioxidants with anti-inflammatory properties.

Health score:

Recommended: Clearspring Organic Toasted Sesame Oil

‘Vegetable’ oil

Vegetable oils are generally blended from several different refined oils such as rapeseed, sunflower, corn and/or soya. The health benefits (or otherwise) depend on how they’ve been processed.

Generally, these oils are high in PUFAs, so they’re unstable when heated and susceptible to oxidation. They shouldn’t be used for shallow frying but are suitable for deep frying if used no more than once, Prof Grootveld says.

Calories per tablespoon: 124

Typical smoke point: 204C

Suitable for: Deep frying if the oil is not re-used, but not shallow frying.

Healthiness: Overall vegetable oils are considered healthy in moderation, especially if they are used to replace saturated fat in the diet.

Health score:

(or 4/5 depending on production methods)

Recommended: Olivio Blended Olive and Vegetable Oil

Butter

Butter is adored for its flavour and while also good for cooking, it’s not a health food. “Butter (and lard) are fully saturated so are more stable when heated,” says Parker. “But from a health perspective, as they can raise blood cholesterol levels, which is associated with an increased risk for heart disease, they are recommended to be consumed in small amounts.”

Calories per tablespoon: 124

Typical smoke point: 150-180C

Suitable for: Frying or sautéing at low temperatures.

Healthiness: Should be consumed in small amounts due to saturated animal fat content.

Health score:

Recommended: Estate Dairy cultured butter

Ghee

Ghee is an Indian version of clarified butter, which means it’s been melted, the water evaporated, and milk solids removed, leaving pure butterfat. Due to its high saturated fat content – virtually the same as butter – it’s resistant to oxidation.

While ghee is made from butter it has a different nutritional profile because the milk solids and casein (a protein) have been removed, which makes it suitable for people with lactose intolerance.

Calories per tablespoon: 124

Typical smoke point: 150-180C

Suitable for: Frying or sautéing at low temperatures.

Healthiness: Ghee is no better than regular butter in terms of its nutritional profile, being very high in saturated animal fat, but it can be used by lactose intolerant.

Health score:

Recommended: Superghee