All You Need to Know About Cooking Oils

I chose the topic for this post because I have a genuine interest in what ACTUALLY constitutes a good cooking oil. There’s a lot of hearsay around the topic, with many people swearing by this or that oil, but no actual idea why it’s better than the rest. Certain people will tell me that they’ve heard a particular oil is best for high heat cooking, but when I pose questions relating to smoke point and oxidation, the response is a sort of panicked confusion and a rapid change of topic.

And let’s face it, if you’ve gone paleo, primal, or just about any diet which realizes that saturated fat is a GOOD thing, oils are your best friend in the kitchen (and elsewhere, of course!). It’s time to know their strengths and weaknesses so you can enjoy all their benefits without denaturing their nutrients or pouring carcinogenic compounds into your body.

Let’s start with the basic questions that you need to ask when choosing the right cooking oil.

What type of fat is it?

There are two types of oil you can buy on supermarket shelves: saturated and unsaturated. Saturated fats are the simplest of these two groups, and the most stable. A good way to tell whether you’re dealing with a saturated fat is knowing that they turn solid at room temperature. Commonly used saturated fats include:

• coconut oil
• palm kernel oil
• butter
• ghee
• lard
• chicken fat
• tallow

Unsaturated fats are a little more complicated, and come in the form of either monounsaturated, polyunsaturated, and trans unsaturated. Commonly used unsaturated fats include:

• canola oil
• flaxseed oil
• soybean oil
• nut oils
• avocado oil
• hemp oil
• sunflower oil
• olive oil

You get the idea. While every oil contains varying ratios of each kind of fat (olive oil contains 73% monounsaturated, 14% saturated, and the rest polyunsaturated, for example), generally speaking the saturated fat group contains primarily animal-based oils, plus coconut and palm kernel. The rest is primarily unsaturated.

Another useful thing to know is that saturated fats and monounsaturated fats are more resistant to heating or cooking. This is due to the fact that they have less bonds, and are therefore less susceptible to chemical reactions which occur under high heat conditions. Polyunsaturated oils, like corn, walnut or sunflower oil, have multiple bonds and so are more likely to become denatured under heat. Trans unsaturated fats (look for the word “hydrogenated” in the ingredients of a product) should just hands-down be avoided.

What is the oil’s smoke point?

An oil or fat’s smoke point is the temperature at which it starts to produce smoke. Pretty straightforward so far, right? Treat this smoke as a warning sign (Tolkien fans might like to envisage the famed Beacons of Gondor, if reality is a little to dull for their taste) – it signifies the point at which your oil is beginning to break down due to heat.

When the oil or fat reaches this point, the free glycerol groups contained within it begin to get converted into acrolein. Acrolein is one of the chemicals found in cigarette smoke, and has been classified as a carcinogen. Thus breathing in the smoke from oil when it reaches it’s smoke point may be similar to breathing in the smoke from a cigarette. Nasty.

Here’s a list of oils and their corresponding smoke point, for some light bedtime reading:

The U’s in brackets next to some oils indicates that they are unrefined, while the R indicates refined. You’ll notice that the refined oils have a much higher smoke point than unrefined oils. Many paleo people may also be somewhat dismayed to see the low smoke point of butter, unrefined coconut oil and lard.

What is the oxidative stability of the oil?

While considering the smoke point of a cooking oil or fat is important, the oxidative stability of that same oil or fat is even more so. The oxidative stability of an oil refers to its ability to resist oxidation. Oxidation occurs when a fat molecule loses a hydrogen atom, allowing it to turn into a free radical.

Free radicals are highly volatile, and due to the way they interact with and attack our cells, can be seriously detrimental to our health. An increase in free radicals in your body means an increased risk of developing a wide range of diseases, and speeding up the aging process.

When oxidation occurs, an oil or fat becomes rancid. People know when an oil has become rancid due to oxidation as it tastes “off”, has a bad smell, or looks a bit weird.

Choosing the right oil for the task at hand

After reading the above, it’s possible you’re even more confused than before. Sorry about that. The point is, there’s no standalone winner when it comes to oils and fats – each has it’s own quirks, and can even vary considerably depending on whether it’s refined, unrefined, expeller pressed, cold pressed or chemical-extracted. You have to weigh up the various attributes of each and only use a given oil when it doesn’t have a high risk of oxidizing or smoking.

To help you in your quest, here’s a few pointers to keep in mind to ensure you get the best (not the worst) from your oil:

• Temperature: no matter what the oil, the lower the cooking temperature, the better. Know your oil’s smoke point, and stay well below it.
• Light: the sun’s wavelengths can increase the rate of oxidation. Try to buy oils which come in dark bottles (not really possible for coconut oil, but then it is fairly resistant to oxidation anyway), and store your oils in a cool dark place to increase their shelf life.
• Re-use: try to avoid re-using your cooking oil, as each time it is cooked with it’s smoke point lowers.
• Antioxidants: considering things like heating, air and light exposure can accelerate your oil’s rate of oxidation (rancidity), choose oils with higher levels of antioxidants. These antioxidants, found in high numbers in oils like avocado, olive, coconut and butter, actively offset the destructive damage free radicals wreak on your body. They can therefore help to neutralize the creation of free radicals during the process of oxidation.

Our top paleo-friendly cooking oil picks

With the proviso that, based on the above, there’s no clear-cut winner in the cooking oil contest, we DO have a few top picks. Here’s our thoughts:

• Avocado oil: a good all-rounder. Has a high smoke point, particularly in the case of it’s refined form (520ºF), and is loaded with antioxidants (particularly vitamin E) so it doesn’t oxidize easily. Use for things like pan frying, grilling, roasting and in salad dressings and marinades.
• Butter: delicious and loaded with an amazing range of nutrients when it’s from grass-fed sources, butter is unfortunately not great for cooking. It has a low smoke point, so should only be used for low heat cooking such as baking or slow-cooking. Has a short shelf-life and can become rancid quickly, so consume ASAP and store in an airtight container in the fridge.
• Coconut oil: Once again, high in antioxidants, and very resistant to oxidation. Has a long shelf life, but should still be stored in a dark place if possible. It does have a low smoke point, however, so stick to low-heat cooking. Switching to refined coconut oil means you can cook at medium heat without creating smoke, but you lose a lot of the antioxidants so it’s a bit of a trade-off. Good for baking and smoothies!
• Ghee: if you were disappointed at butter’s low score in the cooking department, ghee is your savior. Ghee retains much of the delicious richness of butter, has a slightly sweeter taste, and most importantly has a very high smoke point. This means it’s great for high heat cooking like pan frying or grilling, and has a long shelf life. Go for grass-fed ghee, if possible.
• Lard and tallow: not great in terms of nutritional profile, but otherwise a great option for medium-heat cooking, due to their smoke point of around 390ºF. They’re also fairly resistant to oxidation, particularly in the case of tallow (beef fat). Really only good for cooking (it’d be a little weird to drizzle some warm lard on your garden salad).
• Olive oil: despite claims, olive oil is still a good option for cooking, however the smoke point differs considerably between olive oil types. Extra virgin olive oil is the healthiest choice in terms of lack of refinement and therefore level of nutrients, which incidentally means it is highly resistant to oxidation. It does, however, have a low smoke point at 320ºF, making it suitable only for slow cooking or sautéing (great for salads and marinades though!). Virgin olive oil is slightly more refined and so has less nutrients and is a little more prone to oxidation. With a smoke point of 420ºF, however, it’s great for medium-heat cooking such as pan frying and roasting. Only buy olive oil in dark bottles and store them in a dark place to avoid rapid rancidification!

That’s a lot of info to take in, but I hope it helped to clear things up a little. Next time someone asks you which oil you think is best, you can bedazzle them with your oil and fat know-how.