What’s the best… Oil?

This is the first in a new series I’m creating looking at different foods or aspects of nutrition and comparing and debating what is the best. I’m researching and collating information so I can provide you with some answers and help you to make informed choices about what you eat. Spoiler alert – there is rarely a best anything sometimes one thing is best for one scenario and another is best for something else but I’ll be giving the facts and providing my conclusions and opinions for you to make your own mind up on.

The first topic is a bit of a controversial one: What’s the best oil? There are some who advocate for completely oil-free cooking and others who douse everything in it (and of course there are those who fall somewhere on the spectrum in between).


Types of oils – the science part

Saturated / Unsaturated

There are two types of fats within oils – saturated and unsaturated. These terms describe their composition; unsaturated fats contain one (monounsaturated) or more (polyunsaturated) double bonds in their molecular structure, whereas saturated fats have no double bonds. Oils contain fats and are often a mix of saturated and unsaturated but are often classified based on the predominant fat within them.

Length of fatty acid chain

These bonds between the molecules hold the chains of fats together, the chains can be short, medium or long. Short and medium fatty acid chains are absorbed directly into the blood stream and long chains are taken to the liver to be metabolised.

Refined / Unrefined

Cooking oils are sold in both their unrefined and refined state, which simply refers to whether or on the oil has been extracted using heat/chemicals. Unrefined (can be labelled as cold-pressed, virgin or extra virgin) means no heat has been used when extracting the oil so more nutrients and enzymes will still be present in the oil. Refined oils have been treated to have some nutrients and enzymes removed so they have a higher tolerance for being used at higher heats; these have a longer shelf-life but not as many nutrients. The temperature an oil can be used at before it starts to smoke and these chemical reactions start to occur is called its smoke point.

Whilst you could say unrefined oils are healthier because they retain more nutrients, if used at high temperatures these oils lose their nutrients and flavour and produce free radicals and compounds which we don’t want to be ingesting. Whilst refined oils contain less in terms of nutritional benefit, if used at higher temperatures they won’t produce the same compounds as their unrefined counterparts.

It all comes down to finding the right oil for the task at hand.


The most common oils

Let’s delve a little deeper into the types of oils you’d find at the average supermarket:

Olive Oil

Olive oil is extracted from olives and rich in monounsaturated fatty acids and antioxidants. Studies have found that oleic acid, the main fatty acid in olive oil, reduces inflammation. There is also evidence that the nutritional composition of extra virgin olive oil has positive effects on gut microbiome composition. As well as providing protective benefits against cardiovascular disease. This does not mean we need to consume large volumes of the oil but olive oil as a type of oil has been shown to benefit health rather than harm it.

For the beneficial components of olive oil to be present it needs to be extra virgin olive oil which has not been processed in the way refined, generic, olive oil is. So be sure to purchase the higher quality oil and make sure it comes in a dark glass bottle as exposure to light can change the composition of the oil.

Rapeseed Oil

Rapeseed oil comes from the rapeseed plant and belongs to the cabbage family. It is known as both rapeseed oil and canola oil, rapeseed oil is used industrially and canola is used in cooking, in the UK the ‘rapeseed’ oil in the supermarket is not the industrial stuff but is in fact the cooking ‘canola’ oil. Rapeseed oil is high in unsaturated fat and is a good source of the omega 3 fatty acid, alpha-linolenic acid it is also high in omega 6 fatty acids. It has an omega 3 to omega 6 ratio of 1:2 which is considered to be a health-promoting balance of these fatty acids.

These fatty acids help reduce inflammation in the body and provide cardiovascular benefits too. Rapeseed oil is also high in vitamin E which supports skin health. Rapeseed oil is also pretty flavourless making in a useful neutral oil to use.

Coconut Oil

Coconut oil comes from the meat of mature coconuts from coconut palm trees. It contains over 80% saturated fat which is the type of fat which can increase our risk of heart disease if eaten in high quantities. Studies show reducing saturated fat in the diet can reduce the risk of developing heart disease. However, the saturated fat contained within coconut oil is made up of 65% medium-chain triglycerides (MCT) which is a quick source of fuel which your body can metabolise and use quicker than long-chain triglycerides. Coconut oil is also a good source of vitamin E, beneficial for skin health. If has also been shown to improve skin health through moisturisation and reduction of skin inflammation when used directly on the skin. Lastly, coconut oil is a good source of antioxidants. Being high in saturated fats makes it an oil you want to use less frequently than others but it does contain some healthful benefits.

Sesame Oil

Sesame oil is made from raw, pressed sesame seeds. Sesame oil is high in unsaturated fat (82%) and is rich in omegas 3, 6 and 9. Good for your heart and helpful with reducing inflammation. It is also high in antioxidants and quite a lot of studies have been carried out looking into the properties of sesame oil and their potential health benefits but only on animals, more needs to be done looking at the specific impact on humans so I won’t go into the speculative benefits here. You will often find sesame oil in the supermarket as toasted sesame oil, this oil has a stronger sesame flavour and a lower smoke point than standard sesame oil and is not suitable for frying with but is great to add flavour to dressings, marinades or as a finishing element to a dish.

Avocado Oil

Avocado oil is made from pressing avocado fruit. It has a mild, neutral flavour and a very high smoke point. It’s similar to olive oil in terms of its nutritional aspects with 70% of the fat in avocado oil coming from oleic acid which we know from earlier helps to reduce inflammation. Avocado oil does have a high omega 6 to omega 3 ratio which is not preferable, however, the total amount of omega 6 is not very high. Being high in unsaturated fat, avocado oil may be good for heart health. Avocado oil is also rich in vitamins A and E, great for the health of our skin and hair. Like sesame oil, most research into avocado oil has been carried out on animals and more human trials need to be carried out to gain better insight into the benefits of this oil.


Smoke Point

Whilst it’s clear different types of oils can provide potential health benefits, these may be remove, or worse, have a potential negative impact on our health, by exposing them to too high a temperature in cooking. Below is a list of smoke points of different oils:

As you can see when cooking at high temperatures it may be better to use a refined oil so the risk of producing harmful compounds is reduced. Whilst using oil in this way will produce less benefits to health it can increase the flavour of food and the fat can help increase absorption of various vitamins within the food consumed. Avocado oil seems to be the oil with the highest smoke point in it’s unrefined form.


Summary

Unrefined oils (cold-pressed, virgin) retain beneficial nutrients which are processed out of refined oils. These nutrients can turn toxic if the oil is used when cooking at high temperatures so if using an oil in dressings or when cooking at low temperatures unrefined is best and when roasting/stirfrying foods at high temperatures it may be better to stick to the refined versions. Unrefined avocado oil may be the best to use at high temperatures as it retains those beneficial nutrients but if using in a dressing/marinade extra virgin olive oil or rapeseed oil might be preferable. In baking you may wish to use rapeseed oil due to its neutral flavour.


Conclusion

There is no one best oil.

They all have different nutrient profiles, some are better with higher heat and they all have different flavours. Find a couple of oils which work for you, be mindful of their smoke points and use them to enhance dishes and add flavour but don’t make them the star of the show.

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