Which oil for cooking?

Before looking at what to consider when choosing an oil for cooking, let’s understand a bit about oils in general. Plant and animal fats that are liquid at room temperature are usually referred to as oils. The technical term for fats and oils is lipid. There are many different types of lipid, and we need them for our health and wellbeing just as much as we do other nutrients.  
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Our body can’t make certain fats
Our body makes many of the fats we need, but there are two types that we can’t build, and these must be obtained from the food we eat - for this reason, they are referred to as ‘essential’ fats.

​There are two families of essential fats: omega-3 and omega-6 types.  Omega-3 fats are plentiful in flaxseed, and there are small amounts in hemp, walnut and soybean – green leafy vegetables are also a source.  
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Other sources of omega-3 fats
Marine omega-3 fats are preferred sources of these essential fats – plant sources can be converted to marine omega-3 fats, but only in small amounts.  Fish and algae are a source of the EPA and DHA omega-3 fats that make up the largest part of lipid in our brain.  By the way, fish obtain their essential fats from algae.

Sources of omega-6 fats
Omega-6 fats are abundant in safflower, sunflower, walnuts and corn.  Sesame, chestnut and peanuts have medium amounts of omega-6 fats and there are smaller amounts in almonds and cashews – it’s very low in coconut and palm nut.

​Our diet has plenty of omega-6 fats
The diet of most people has more than enough omega-6 fats. Omega-6 fats are good for the heart, help improve sensitivity to insulin and, contrary to popular belief, do not increase inflammation in our body – they probably help do the opposite!

... But short on omega-3 fats
​The best source of these is oily fish, but few people meet the recommendation to eat one portion of oily fish each week.  Omega-3 fats are good for the heart and are anti-inflammatory, so we should be aiming to get more of these from our diet. For those who don’t eat fish, walnuts are a source of omega-3 and omega-6 fats.
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​What makes an oil a good choice for a dressing or cooking?
The type of fat that makes up the oil and its smoke point are two things to consider when making a choice from the array of oils available.

Type of fat

Fats can also be classified as either saturated or unsaturated (monounsaturated and polyunsaturated) and this is what primarily determines whether a fat is considered to be ‘healthy’ or ‘less healthy’.

Saturated fat raises LDL blood cholesterol (the less-healthy type), whereas unsaturated fat (such as omega-6 and omega-3 fat) help lower LDL cholesterol and increase HDL cholesterol (the healthy type). The aim therefore is to eat fewer sources of saturated fat and more sources of unsaturated fat.​

Smoke point

Oil becomes unstable when cooked above a certain temperature and this is referred to as the smoke point.  Each oil has its own smoke point – the temperature at which the oil breaks down and creates free radicals, which are potentially harmful to our body.  Heating oil above its smoke point creates acrolein, which creates a burnt flavour and can be harmful to lungs when breathed in.
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What about coconut oil, then?

In recent years, there has been renewed interest in coconut oil and whether it helps protect heart health or harms it.  A review in 2020 found that coconut oil when compared with other plant oils and animal oils significantly raised HDL cholesterol (the healthy type). It also raised LDL cholesterol (the less-healthy type) more than did other plant oils, but less than animal oils.

Coconut oil is high in saturated fat, but it has a high smoke point. Each of us must weigh up the pros and cons of using a particular fat, either as a dressing or for cooking at high temperatures. The taste of the meal and the occasion is also a consideration – eating should be enjoyable and sometimes the health value of a particular meal on that special occasion is not an important consideration!

Download information on fat profile and smoke point of various oils.

Tony Hirving
Dietitian