A Dietitian's Guide To Cooking Oils
Updated: Mar 4, 2021
There’s enough going on at the end of the day to not need to stress over which cooking oil to choose- coconut, olive, vegetable? What’s really best? Is it worth paying more for “extra virgin”?
Here’s a dietitian’s guide to selecting the best cooking oil. Hint: Extra virgin olive oil wins!
Getting our fats straight
One of the first things to consider are the types of fats in our diet. There are four groups: monounsaturated, polyunsaturated, saturated and trans fats.
Mono- and polyunsaturated fats are known as “good” fats, the ones we want more of in our diet. They’re typically found in plant sources like olives, avocado, nuts and seeds, as well as fish.
Saturated and trans fats are known as “bad” fats that are associated with worse health outcomes, increasing our “bad” or LDL cholesterol.
Saturated fats are being misrepresented lately, and findings are being misconstrued. Yes, our understanding of these fats have clarified, but they have not been found to be beneficial when high in our diet. For example, dairy: plain milk, yoghurt and cheese are considered "neutral" for HEALTHY individual's hearts, while butter and cream are not. These fats, overall, are considered "unhealthy" fats linked with increased "bad" cholesterol, increasing our risk of heart disease.
Trans fats worsen our health, increasing "bad" cholesterol, decreasing the "good" and increasing heart disease risk. These appear in our diet mainly through highly processed and/or fried foods, and is grouped with saturated fat as many of these foods overlap as sources for both.
Oil stability is important
Stability? I know, it sounds really odd, and no, I don’t mean smoke point.
The smoke point was previously used to suggest the stability of a cooking oil- suggesting that heating an oil beyond it’s smoke point (or the point there would be ‘smoke’ from the oil when heated), increases the chances of the oil being oxidised or damaged.
The smoke point isn’t actually the strong indicator of an oil’s ability to withstand heat or it’s safety and “healthiness” when heated- it does not suggest how the oil will change over time as there are more factors in play.
When oil is broken down, from being heated, there are compounds, like polar compounds, produced that we want to be mindful of for our health. Though, the more stable an oil is, the more resilient it is to this change. However, it’s important to note, most oils need to be exposed to heat for a prolonged time for ~30-60 minutes before really seeing changes in compounds produced (also relevant for kitchens reusing oils).
Key factors to consider here are:
The types of fats it is composed of: those higher in polyunsaturated fats will be less stable due to the chemical structure.
Antioxidants: oils containing antioxidants are more stable- they protect the oil like we say they protect our cells!
Production: if an oil is heavily processed and refined, then it will be less stable (so extra virgin and virgin oils will be more stable, with yes, the extra virgin being most stable)
Let’s look at the different oils
Olive oil is produced from…you guessed it, olives! It is highest in monounsaturated fat (76%), followed by saturated and then polyunsaturated fat.
Extra virgin olive oil (EVOO) is the most stable of all the olive oil varieties due to it’s antioxidant content, low polyunsaturated fat content and low degree of processing. That means it is absolutely safe to cook with, and at high heats. There’s a whole bunch of evidence supporting EVOO use for heart, brain and metabolic health.
Where to use it: It’s a great all-rounder. Stir fry with it, bake with it, dress your salads, drink it if you feel you must.
Canola oil, despite some confusion, it a healthy mix of mono (59%) and polyunsaturated (34%) fats. These polyunsaturated fats in canola oil include omega-3s, which are also great for our hearts. It isn’t as stable as olive oil, being one of the least stable at high temperatures overall.
Where to use it: It doesn’t have a strong taste so can be used in all cooking options, though using it in dishes that require lower heats and less cooking time is best suited.
Unfortunately, despite all the hype, most of coconut oil is saturated fat ( more than 90%!). Coconut oil has been shown to increase “good” HDL cholesterol, yes, but it’s also been shown to increase “bad” LDL cholesterol too- this is not ideal. Unfortunately, it isn’t a winner for me to have daily.
Where to use it: I’ve heard great reviews from putting it in your hair!
Peanut oil is a little higher in saturated fat than other cooking oils (36%), though it still provides a healthy amount of monounsaturated fat (45%) and isn’t too high in polyunsaturated fat for cooking (19%), making it more stable than many other cooking oils, too.
Where to use it: having a slight nutty flavour, it works really well in Asian-style dishes.
Rice Bran Oil
Rice bran oil has near equivalent contents of mono- and polyunsaturated fats (near 40% each), and is lower in saturated fats (20%).
Where to use it: Rice bran oil doesn’t have a strong flavour, so can easily be used in most cooking. It isn’t particularly stable unfortunately, so best suited to short cooking times.
Sunflower oil fatty acid composition varies depending on it’s quality and the extent to which it’s been processed. Typically (unless high oleic) sunflower oil will be high in polyunsaturated fat (around 66%), making it less stable at high heats and for long periods of cooking.
Where to use it: sunflower oil also have very little taste, and so is easily used in many dishes. Due to stability, would be best in quick dishes at lower heats.
Sesame oil has a similar content of both mono- and polyunsaturated fats (around 40%), and is lower in saturated fat. It is much like rice bran oil in this regard.
Where to use it: Asian-style dishes- you’ll recognise the flavour quickly, as a little goes a long way! Stir-fry and noodle dishes are best with this!
Avocado oil has a similar fatty acid profile to EVOO, with 76% monounsaturated fat, then saturated fat and some polyunsaturated fat. It does go rancid a little easier than EVOO, but it’s a favourite in my house. It hasn’t been as well studied as EVOO for health benefits, though is quite stable at high heats.
Where to use it: in everything, it doesn’t have a strong taste and is easy to incorporate whether it’s a higher heat or longer cooking time, it’s fine.
Grapeseed oil is the highest in polyunsaturated fat of all the oils here, being around 73%. It’s a particularly unstable oil at high heats and long temperatures, so it isn’t my preference.
…is not made from vegetables!
Vegetable oil is normally a mix of soybean oil and canola oil, but can include high saturated fat oils like coconut and palm. Check the label to see what you’re buying here. It will typically be higher in polyunsaturated fat and monounsaturated fat, and highly refined…so a less stable option.
So, EVOO and avocado oil win
EVOO is my #1 choice due to it’s minimally processing, high levels of antioxidants, and good fat ratios. This oil contains lots of beneficial goodies and it stable at high heats for long cooking times, more so than the refined or just virgin options.
Avocado oil has a similar profile and stability, so it’s great to include too.