From cooking up a quick stir-fry to making an elaborate Sunday roast, oil is one of the key ingredients in most of our go-to recipes. But if you’ve been on social media recently, you’ll have come across countless influencers and content creators slamming certain oils. From inflammation to chronic disease, there are people out there who suggest that common cooking oils, including sunflower and rapeseed oil, can cause us all kinds of issues.

Even if you haven’t stumbled across this section of wellness internet, a quick scan of a supermarket shelf will tell you that there’s a dizzying array of oils out there. While they may all look similar, there are some vital differences between the different oils you can buy – especially when it comes to firing them up for cooking. 

Far from just a good way to add flavour to your favourite salad, oil can be a key part of achieving a healthy, balanced diet. “Oils can provide sources of monounsaturated fats that are important for supporting healthy heart, brain and joint function,” explains Jenna Hope, registered nutritionist and author of How To Stay Healthy.

Fats also play an important role in energy production and nutrient absorption. “Fats are important for many functions, including nutrient absorption, cell structure, organ protection and hormone production,” says Sophie Medlin, director and specialist dietitian at City Dietitians.

Generally speaking, around 30–35% of our total energy intake should come from fats, with less than 5% coming from saturated fats.“Oils fit nicely into this,” says Hope, explaining that the exact amount of oil you consume should be factored against how many other sources of fat you regularly have in your diet such as nuts, avocado, oily fish and full-fat dairy.

But, the kind of oil we choose to eat is important. “Choosing the right fats for your diet is important – some are really beneficial and others can be harmful if taken in the wrong quantities,” says Medlin.  

All the oils you see on supermarket shelves are named after the seed, fruit, plant or grain from which they’ve been extracted. They are made up of chains of fatty acids. If these fatty acids are held together by single bonds, they are ‘saturated’ and if they are held together by double bonds they are ‘unsaturated’. It’s the oils that are mainly formed of saturated bonds, ie ‘saturated fats’, that are best consumed in moderation. 

Overconsumption of saturated fats can increase your risk of high cholesterol and cardiovascular disease. Scientific research backs up advice to reduce the consumption of saturated fats in our diet. For example, a study from The Italian Society of Diabetology found that the risk of death was reduced by 19% when the subjects replaced 5% of calories from saturated fats with the same number of calories from polyunsaturated fats, which come from salmon, sunflower oil, nuts and seeds. 

Fats change in structure when they’re heated, meaning that some fats that are healthier for us at room temperature aren’t as good for us when they’re heated. Even some of the most nutrient-packed varieties out there aren’t always the best for cooking with.

“Extra virgin olive oil, for example, loses some of its benefits when it is heated, but it doesn’t become bad for us; you’re just wasting money using it for cooking,” explains Medlin. This means looking for oils that have higher ‘smoke points‘ – the point at which the oil becomes rancid and oxidises while it’s being heated up.

“Once an oil passes its smoke point the beneficial properties are degraded and the consumption of it can increase free radicals in the body,” says Hope. Free radicals are unstable molecules made during chemical changes that take place in our cells. “High levels of free radicals can contribute to cell damage, cell death and inflammation,” says Hope.

Expensive, ‘cold-pressed’ oils are some of the most nutritious on the market; however, this doesn’t mean they are the best option when it comes to cooking. “Cold-pressed oils are expensive and you will lose some of the benefits when you cook with them,” says Medlin. “Furthermore, they have a lower smoke point and develop harmful compounds when heated.”

Definitive answers about the best oils to cook with can vary between nutritionists. It also depends what kind of meal you’re cooking and how long you’re cooking an oil for. But generally speaking, olive oil and avocado oil are often singled out as some of the best oils to use in your recipes.

Olive oil

Olive oil is famous for having a myriad of health benefits. Packed with naturally occurring antioxidants and polyphenols it has anti-inflammatory properties and can help manage cholesterol and improve our heart health.

“Olive oil has one of the best profiles of unsaturated fats, it can withstand higher temperatures and it also contains beneficial plant compounds,” says Hope.

The bonds in olive oil mean it’s more resistant to high temperatures and is less likely to oxidise when it’s heated. However, it’s important to choose olive oil wisely.

Medlin advises avoiding expensive ‘extra virgin’ olive oils and opting for cheaper versions instead to cook with. “The reason for this is that some of the benefits of olive oil are lost when it is heated so there isn’t any point in cooking with an expensive olive oil. I generally save more expensive extra virgin olive oil for drizzling on salads, but this is more of a cost calculation than a health calculation.”

Cheaper virgin olive oil has a smoking point of 210°C, so Medlin recommends it for roasting in the oven and using on food you’ll be cooking at lower temperatures. “For roasting in the oven, olive oil is a great choice as it has many health benefits and it is unlikely to reach its smoke point in the oven.”

Avocado oil

Avocados are packed with nutritional brilliance. They contain protein, omega-3 fatty acids and essential nutrients such as potassium and vitamins E and B, making their oil a brilliant choice for adding to meals.

“Much like olive oil, avocado oil is thick and flavoursome and is stable at high temperatures,” says Hope. Its high smoke point (270ºC for refined varieties and 190-205ºC for unrefined) means it’s a great oil for more intense cooking.

“For frying at higher temperatures, avocado oil is a better choice than olive oil,’ explains Medlin. 

Seed oils have recently come under fire on social media for being inflammatory and containing unhelpful fatty acids, but is there any credibility to these claims? According to Medlin, there’s no scientific evidence to support the demonisation of seed oils, such as sunflower oil, rapeseed oil and sesame oil.

“Seed oils do contain more omega-6 fatty acids and getting the ratio of omega-3 to omega-6 in favour of omega-3 is a good idea – excess omega-6 oil is less favourable for our health. However, using seed oils in moderation for cooking is perfectly healthy and not something we need to be concerned about,” says Medlin. “People also say seed oils are pro-inflammatory, but it is much more likely that the typically processed foods that contain seed oils are the cause of the problem rather than the seed oils themselves.”

When choosing a seed oil to cook with, Medlin suggests looking for varieties that are 100% seed oil to avoid any that contain anti-foaming agents and other additives that aren’t so good for us. 

Again, the answer to this question varies from nutritionist to nutritionist, but generally speaking, oils high in saturated fat are the least healthy to cook our meals with.

“Coconut oil, butter and ghee all contain saturated fat, which can raise our cholesterol and cause heart problems,” says Medlin. It’s a conclusion supported by scientific studies. A 2021 study published in the peer-reviewed BMC Medicine journal, looked at the links between our daily cooking oil intake and the onset of chronic diseases, including cardiovascular issues and diabetes. Studying 521,120 participants, it found that consumption of butter and margarine, both high in saturated fats, was associated with higher mortality. Whereas replacing butter and margarine with olive oil was associated with lower mortality.

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