What oil should you cook with? Making sense of the confusion

If you’ve ever stood in front of a supermarket shelf of oils, wondering which one is 'the healthiest', you’re not alone.

Olive oil, rapeseed oil, coconut oil, sunflower oil... every few months there seems to be a new headline claiming one is good for you and another will quietly destroy your health.

The truth is, it’s complicated.

Nutrition science evolves, studies don’t always agree, and marketing claims add yet another layer of confusion.

As someone who helps people in midlife optimise their metabolic health, I see this all the time: clients trying to do the right thing, but feeling lost in the noise.

So, let’s unpack what we actually know, and how to make sense of it in everyday cooking.

Types of fats in our commonly used cooking oils

Saturated fats, found in butter, ghee, coconut oil and meat, are more stable when heated, which makes them good for high-temperature cooking.

While they can raise LDL cholesterol, newer research suggests the effect depends on the overall diet and what the fats are replacing.

A diet high in saturated fat and refined carbohydrates, for example, is very different from one where those fats appear alongside plenty of fibre, vegetables and omega-3s.

You can tell a saturated fat because it is more solid at room temperature.

Monounsaturated fats, such as those in olive, rapeseed and avocado oils, are widely seen as heart friendly.

They’re less likely to oxidise when heated and form a cornerstone of the Mediterranean diet, which consistently links to better metabolic and cardiovascular outcomes.

Polyunsaturated fats, found in sunflower, rapeseed, soybean, walnut and flaxseed oils, contain essential omega-6 and omega-3 fatty acids.

These are vital for brain and hormone health, but they’re also more delicate – too much heat or processing can damage them.

It's worth noting that many oils contain more than one of these types, for example rapeseed contains around 60% monounsaturated and 40% polyunsaturated,

Processing and refinement

Highly refined oils such as standard 'vegetable oil' or 'light' olive oil are treated to remove impurities, neutralise flavour and extend shelf life.

This treatment process can strip away antioxidants and beneficial plant compounds (such as polyphenols).

By contrast, extra virgin olive oil is minimally processed and retains those protective compounds, which is why it’s consistently linked with reduced inflammation and improved heart health.

Other oils may be labelled 'cold-pressed' or 'virgin', which also indicates minimal processing.

In summary, more processed/refined = fewer beneficial compounds.

An oil's ability to withstand heat

How ‘good’ an oil is for cooking or heating depends on three main factors:

• Type of fat – saturated, monounsaturated and polyunsaturated fats differ in how easily they oxidise (their stability). Saturated fats are the most stable, polyunsaturated the least.

  
  

• Smoke point – the temperature at which an oil visibly starts to smoke. Beyond this point chemical changes occur, producing off-flavours and potentially harmful compounds. Smoke point is influenced by processing/refinement, impurities and the presence of protective compounds like antioxidants.

• Protective compounds – natural antioxidants and polyphenols help to stabilise oils during heating, slowing oxidation and reducing the formation of harmful by-products. Oils with higher levels of these compounds (those that are less refined such as extra virgin olive oil), can be more resilient than their smoke points alone suggest.

  
  

Here are some approximate smoke points, to give a sense of range:

• Avocado oil (monosaturated): up to 250°C

• Sunflower oil (polyunsaturated): 225–245°C

• Light olive oil (monosaturated): 200–245°C

• Rapeseed oil (mono and poly): 200–230°C

• Extra virgin olive oil ((monosaturated): 190–210°C

• Coconut oil (saturated): 175°C

• Butter (saturated): 150°C

So, for example...

Saturated fats like coconut oil or butter are chemically stable even though their smoke points aren’t the highest.

Refined oils often have higher smoke points, making them practical for high-heat cooking, but the refining process removes many of the polyphenols and antioxidants that that can protect from the oil from the heat and offer health benefits.

Extra virgin olive oil, on the other hand, is less refined and rich in polyphenols, which help protect it from oxidative damage. This makes it surprisingly resilient – even more so than highly processed or ‘light’ olive oils, despite their higher smoke points.

In other words, an oil’s real-world stability takes into account the type of fat, how hot it gets before it smokes AND the natural compounds within it that protect it when heated.

(I know, my head hurts a bit now too!)

What this means practically

High-heat cooking (≥200°C, e.g. deep frying, stir-frying, searing, roasting at high temperatures) needs an oil to be able to withstand some serious heat. These include:

• Refined or light olive oil

• Rapeseed oil

• Avocado oil

• Butter and ghee

  
  

For medium-heat cooking (gentle frying, baking), most oils are safe and nutritionally acceptable, including extra virgin olive oil, rapeseed, sunflower and coconut.

For cold uses (dressings, drizzling, dipping), extra virgin olive oil, flaxseed oil and walnut oil preserve the most nutrients and antioxidants.

Vegetable spreads and margarines

You might wonder about vegetable spreads and margarines – are they healthy? The key is in how they’re made.

Traditional margarines were partially hydrogenated to turn liquid oils into a more solid spread (increase their saturation).

This process created trans fats, which are strongly linked to higher LDL cholesterol and increased cardiovascular risk.

Modern margarines no longer use partial hydrogenation; instead, they use fully hydrogenated fats (which don’t form trans fats) or blend liquid oils to achieve a spreadable texture.

They can be a practical choice for spreading on toast or cooking, but don't over-use them; they are made from refined oils and are low in micronutrients and polyphenols compared with whole food fats like extra virgin olive oil.

For midlife metabolic health, moderation and variety are key.

Using a mix of butter, olive oil, rapeseed oil and spreads can help you balance saturated, monounsaturated and polyunsaturated fats, supporting heart and metabolic health while keeping your diet enjoyable.

Industrial seed oils

You may have heard about 'industrial seed oils' - often criticised in the ultraprocessed food debate.

These include oils extracted from seeds like sunflower, soybean and rapeseed, often labelled as ‘vegetable oil’ in the UK.

They are highly refined to increase smoke point and shelf life, but this removes natural nutrients and protective compounds.

You usually find them in ultraprocessed foods, ready-made dressings, margarines, and in bottles.

While industrial seed oils are often criticised for being ultraprocessed, the evidence linking them to harm (such as inflammation) in humans is still limited.

However, that doesn’t necessarily mean they’re the healthiest choice – just that the evidence isn’t clear-cut.

And here’s where one of my favourite phrases comes in: absence of evidence isn’t evidence of absence.

As we have discussed, processing changes an oil’s chemical profile, stripping antioxidants and creating by-products such as aldehydes when overheated.

It’s plausible that, over time, this could impact health, but more research is needed.

The easiest way to avoid industrial seed oils is to avoid ultraprocessed foods as much as possible.

Midlife metabolism and healthy fats

As we move through midlife, hormonal shifts – particularly the drop in oestrogen for women – can influence how we store and burn fat.

Choosing the right fats to cook with can make a difference.

Monounsaturated and polyunsaturated fats support cardiovascular and brain health and can help to counter the subtle inflammation and insulin resistance that tend to increase during this stage of life.

That’s why I encourage clients to focus less on avoiding fat, and more on choosing it wisely – because our brains, hormones and cells all rely on it.

My take – variety is key

The question “what oil should I cook with?” doesn’t have a single answer – and that’s OK.

Evidence evolves.

Context matters.

And the reality is that what you cook, how often, and how much of it you eat will matter far more than the specific oil you use.

So, my best advice?

Vary your oils – each brings something different to the table.

Don’t overheat or reuse them – especially delicate ones.

Enjoy food without fear – balance and variety win every time.

Because good health isn’t about obsessing over one ingredient; it’s about the whole picture.

Concerned about your health and nutrition and need some guidance?

Get in touch if you’d like personalised guidance to help you take charge of your health.

Contact me

Disclaimer

The information and advice I provided here is of a general nature and should never replace individual health or medical advice provided by your doctor or other healthcare professional involved in your care.