Cooking oil – which to use for what and why

Cooking oil – which to use for what and why

Oil has developed a bad reputation for being linked to heart disease and obesity, but like most food theories, many of our perceptions (or misconceptions) about oil have been largely affected by the marketing efforts of big conglomerates to sell their products.
We sat down with MD and physiologist Dr Margo De Kooker to get to the bottom of this slippery subject.

In this blog, you will learn:

  • What are the different types of oil and what is the difference between them?
  • What’s the difference between saturated, monounsaturated and polyunsaturated?
  • Does olive oil become bad for you when heated?
  • Is palm oil a good option?
  • What is the best oil to use for cooking?
  • What is the best oil to eat raw?
  • What is the worst oil to consume?
  • How much oil can I eat per day?  

What are the different types of oil and what is the difference between them?

There are three types of oils – animal fats, fruit oils and seed oils.

  • Animal fats are butter, lard, etc.
  • Fruits oils are olive, avocado, coconut and palm oil.
  • Seed oils are canola, sunflower, flaxseed, soy and nut oils.

According to Dr Margo, the nutritional value of oil (or lack thereof) depends on how hard it is to get the oil from the source ingredient.

Animal fat is already there to use, so it is not processed and, in moderation, is a good form of oil to use. Fruit oils are easy to get out of the source fruit. It doesn’t take a whole lot of processing.

Seed oils, however, need to be heated under pressure to extract their oil. What this means is that the oil will likely be damaged and then may need artificial stabilisers to keep it from going rancid, and colourants and flavourants to make it look and taste palatable.


What’s the difference between saturated, monounsaturated and polyunsaturated?

Saturated fats (animal fats) are solid at room temperature. What this means is that their chemical structure is stable and complete and there is nowhere for oxygen to attach to turn it rancid. This is why butter can sit on the counter and will stay good unless, of course, you live in equatorial countries where the temps go up to 40-50°C.

Monounsaturated fats (fruit oils) are slightly less stable and have one free spot where oxygen can attach.

Polyunsaturated fats (seed oils and fish oils) have multiple spots for oxygen to attach and so can go rancid more easily. There’s nothing wrong with that as such. If seed oils are cold-pressed, they are not harmful in small amounts.

The problem comes in when producers try to make a stable solid out of polyunsaturated fat. Unsure what we mean? Ever wondered why your margarine stays that perfect spreadable consistency? It’s because its seed components have been heated, pressed, processed and, worst of all, hydrogenated to keep it in a solid form. Hydrogenation is the process of chemically altering a substance and renders the product very difficult for your body to process as it damages the product which, in turn, has a higher risk of damaging our cells.

Notes Dr Margo, “Any oil that comes from a seed, unless it’s cold-pressed, will be damaged.” Of course, cold-pressing is more expensive and yields less oil, so for industrially produced oil that is used at, for example, fast-food chains, this would be an unpopular choice.

Oil infusions

Does olive oil become bad for you when heated?

The short answer is no. Every oil has a smoke point. Above that point, the oil becomes damaged and is not good for you. Dr Margo explains that olive oil is rich in phenols and polyphenols – phytonutrients that are good for your body. These can be lost when applying heat, but the oil does not become bad for you until it surpasses its smoke point.

The term extra virgin’ means that the oil comes from the olive’s first pressing. If it is not extra virgin, that means that the olives have been re-squeezed with heat applied and the oil will likely be damaged.

Here is a handy chart on the smoking points of oil, so you can see just how far you can go with heat before the oil is damaged and will do damage to you.

Smoke points of oils
Click image to view as PDF


Is palm oil a good option?

Palm oil has been used for centuries in Asian countries to cook food at a high heat because it has a very high smoke point. Unfortunately, industrialisation meant that big companies realised the benefits of palm oil and this has led to deforestation and environmental damage. You can, however, find sustainable producers of palm oil, and it is a great option for cooking.

What is the best oil to use for cooking?

Olive oil, ghee, coconut oil, ethically-produced palm oil (in South Africa we have a product called HOLSUM that is sustainably sourced palm oil) are good options. Bear in mind that every time you heat an oil, you are damaging it, so Dr Margo recommends that you never reuse oil.


What is the best oil to eat raw?

Extra virgin olive, avocado and coconut oils are good to eat raw in moderation. The best way to eat oil is in its natural form, meaning eating an avocado instead of avo oil.

What is the worst oil to consume?

Avoid vegetable oil as you don’t know what went into it and it will be highly processed. Commercially processed sunflower oil is damaged from the start and should be avoided. Avoid hydrogenated oils like margarine or oils with stabilisers. The main stabiliser that’s used in oils is TBHQ (tert-butylhydroquinone) and is very difficult for the body to process. It’s been linked to obesity, amongst other things. This is found in the oils used in industrial cooking.

So why is damaged oil bad for you? Dr Margo explains that when oils are damaged, they become compounds that damage our cells and set up an inflammatory response in the body. The chemicals involved in the inflammatory response can damage any cells they come into contact with and when this takes place in your arteries, you can get atherosclerosis (buildups of blockages in your artery walls) .

How much oil can we consume daily?

A lot of our cell membrane is made from fat and we need fats as a backbone for almost half of our hormones. This means that a no-fat diet doesn’t serve the body, but you can overdo it. If you want to eat a lot of fat, you cannot eat a lot of carbs and vice versa. Lots of carbs and fats together are a disaster. This is why a deep-fried chicken burger from your local fast-food chain that has been cooked in damaged oil and is loaded with fat and carbs will affect your body for at least two days afterwards.


Not all oils are created equal. That’s why it’s essential to understand the categories to make good health choices. If you would like more information or an individual consultation with Dr Margo, you can contact her via email at

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Lisa Parsons

Lisa is a content writer and strategist with experience across many platforms. She is also a personal trainer and has a keen interest in holistic health encompassing physical, mental and emotional wellness. She enjoys travel, books, puzzles, learning languages, and a buttery Chardonnay.

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