Using oils in cooking: which oil is the healthiest?

With so many oils on supermarket shelves, all claiming to be great for high heat cooking, flavour or heart health, choosing the right one can feel overwhelming.

The good news is once you understand what determines how well an oil copes when heated, it’s much easier to know which ones to use for frying and roasting, and which are better saved for drizzling.

What makes an oil stable for cooking?

The type of fat in the oil matters for both heat stability and heart health.

As oils heat, their fat molecules can start to break apart and form unwanted compounds called lipid oxidation products (LOPs). These form more readily during prolonged high‑temperature cooking (above 260°C) or when oil is reused repeatedly.

In large amounts, some LOPs may contribute to inflammation in the body. Home cooking rarely reaches these extreme temperatures, but an oil’s stability still matters because it reflects how quickly those unwanted by‑products form.

What seems to matter more for both heat stability and heart health is the type of fat in the oil. For most people, the fat profile – rather than the smoke point alone – is usually a more helpful guide when deciding which oils to cook with and which to save for drizzling.

What is the most stable oil for cooking?

All oils are made up of a mix of saturated, monounsaturated, and polyunsaturated fats and each type behaves differently when heated.

• Saturated fats, found in foods like butter, ghee, lard, palm and coconut oil, have a very sturdy structure with no double bonds. This makes these fats naturally heat‑resistant, even though some, like butter, have lower smoke points because of the milks solids that burn early. Once those solids are removed, as in ghee, the fat itself tolerates high temperatures. However saturated fats can raise blood cholesterol levels, so while they tolerate heat well, they’re not the best everyday choice for heart health.

• Polyunsaturated fats, found in oils such as sunflower, corn, and soybean, have many double bonds – lots of ‘weak spots’ that break apart easily when heated. These oils often have high smoke points, which can be misleading, because they’re the least stable at high temperatures. They do provide essential omega‑6 fats, vitamin E, and contain heart‑friendly unsaturated fats, but they’re better suited to low-to-medium heat cooking (less than 170 °C) like gentle sautéing where the oil barely simmers, or baking at low temperatures (around 120-150°C).

• Monounsaturated fats found in oils like olive, rapeseed, avocado and peanut oil have just one double bond. This makes them more heat stable than polyunsaturated oils, while still being high in heart‑healthy unsaturated fats. This balance means are great for most everyday cooking – sautéing, pan frying, roasting, and even hot, fast cooking like stir- frying and searing – and why they’re often considered the best all‑rounders.

You can also find high‑oleic versions of some oils, such as high‑oleic sunflower, safflower, or peanut oil. These oils have been developed to contain much more oleic acid – the same monounsaturated fat found in olive oil.

This means they behave more like olive or avocado oil and stay more stable at high‑heat cooking than their regular version, which contain more polyunsaturated fats.

What are the healthiest oils for frying and roasting?

Refining also plays a big role in how an oil behaves when heated.

Refined oils are any plant oils not labelled ‘virgin, extra virgin or cold‑pressed’. In shops, they may also be labelled as ‘pure’, ‘light’ (referring to flavour and colour, not calories), ‘classic’, ‘regular’ or ‘filtered’ or just oil.

Refining raises the oil’s smoke point and makes it milder in taste.

During refining, flavour compounds and impurities that burn easily are removed. This raises the smoke point and makes the oil more heat‑tolerant, milder in taste and usually more affordable.

This is why most refined versions of oils like rapeseed, olive oil and high-oleic oils are often recommended for higher heat cooking like frying, searing and roasting.

What are the best oils for low or no-heat cooking?

Unrefined oils are less processed, so they keep their natural flavours and antioxidants. Extra virgin olive oil, for example, contains polyphenols linked to benefits for heart and gut health.

You can find unrefined versions – often labelled as virgin, extra virgin, or cold‑pressed – of rapeseed, olive, peanut, sesame, flaxseed, walnut, sesame and avocado oils. Because they have more flavour, and are often more expensive, they are best used for drizzling, dressings, dips, or low-heat cooking.

The takeaway: best oils for cooking

Using a variety of oils can help you balance flavour, cooking needs and heart health. For most home cooks, keeping it simple works best:

• Use refined oils, such as rapeseed or olive oil, for everyday frying and roasting — they’re heat stable and high in unsaturated fats.
• Save unrefined oils, like extra virgin or cold‑pressed varieties, for drizzling, dressings and gentle cooking, where you can make the most of their flavour and antioxidants.
• Try to avoid reusing oil, as this speeds up the formation of unwanted by‑products.
• Whenever possible, choose cooking methods that naturally use little or no oil, such as steaming, baking or grilling.

And remember, even heart‑friendly oils are still high in calories — a good rule of thumb is to use one tablespoon of oil for 4 people.

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