I'm a dietetics student. And, I should probably add, an older one. I changed career paths two years ago and haven't looked back since. Because of what I'm studying, friends have started asking me a variety of health related questions. I find this to be super helpful for my learning, because I'd often start off on the right track answering them, but then realise that I too still get tripped up with the facts.
So I've started making notes of the types of questions people often ask so that I can break it down to be able give a better and more confident answer the next time someone asks the same thing.
Recently a friend with high cholesterol asked which type of oil she should be using. Another asked me what the deal is with coconut oil, and whether she should be swopping her olive oil to be cooking in this.
So I went through some class notes and also looked for reputable research based articles online for an answer to have in my arsenal for future questions on the topic. Next time my answer will sound a bit like this:
When deciding which oil you should be using, ask yourself four quick questions:
- What is the smoking point of the oil?
- What will I be using it for?
- What type of fats does the oil contain?
- How often will I be using it?
Let's start with the smoking point of the oil. This refers to the temperature at which the oil will become unstable and start releasing harmful free radicals and toxic fumes. It's good to be aware of this so that you don't end up frying or browning food in an oil with a low smoking point.
Which brings us to the second question: what will you be using it for? In general, canola oil and sunflower oils are good options for frying and browning, as they both have high smoking points (around 246ºC) and are also low in saturated fatty acids (SFAs). Refined olive oil (note: NOT extra virgin olive oil, but the lighter, refined one) might be the best pick though: it's low in SFAs, it has a smoking point of 225ºC and has the added benefit of being rich in mono-unsaturated fatty acids (MUFAs).
The third question is thus to determine the type of fats that the oil contains. Why does SFA's and MUFAs matter and what do they mean? One can go into detailed explanations on the bonds between the carbon chains in the fatty acids and how they react in your body to explain why scientific researchers and health professionals prefer the one over the other, but in short: Diets high in SFAs have been linked to an increased risk of developing cardiovascular disease and raised "bad" (LDL) cholesterol levels, which can also contribute to developing other lifestyle diseases. On the other hand, research backs MUFAs as having the ability to help lower "bad" cholesterol and raise "good" (HDL) cholesterol, and thereby decreasing the risk of coronary heart disease. Polyunsaturated fatty acids (PUFAs) are also evidenced to help lower the risk of cardiovascular disease when it replaces SFAs in the diet.
Oils highest in MUFAs are extra virgin and virgin olive oil (73%) and avocado oil (70%). Sunflower (69%), grapeseed ( 71%) and soybean (61%) oil are also high in these. Soft margarines also generally have good MUFA and PUFA profiles and are moderate to low in SFAs (about 20%). Choosing soft margarines over hard butters (which contains approximately 66% SFAs) is thus the healthier choice for spreads or baking.
There are of course also a range of other oils available on the shelf:
Sesame oil scores well in the PUFA and MUFA categories (43% each), and is not to high in SFA. Semi-refined sesame oil has a high smoking point (232ºC), making it a tasty option to to fry or sauté Asian dishes in. Peanut oil also has a high smoke point (231ºC) and it's relatively high in MUFAs (49%), too.
Flaxseed oil is a rich source of omega 6 and omega 9 fatty acids, but has a very low smoking point, so it's a better option for dressings. Walnut oil is another great source of omega 3 and PUFAs, but also has a very low smoking point, so it's best used cold.
But you probably still want to know what the deal is with coconut oil, right? This is still a bit controversial. Research on virgin coconut oil found that though it's very high in saturated fat (90%), the type of saturated fat might be healthier than other oils and fats with high SFAs. While it increases "bad" cholesterol, research shows that it can also raise "good" cholesterol. But look at this article by the Dietitians Association of Australia if you're interested to learn more about it. It basically comes down to this: In an effort to prevent disease, researchers don't have enough evidence to promote the use of coconut oil over other more researched and proven healthier choices such as olive oil. So using it in moderation is still recommended.
As with everything in life, don't overdo it.
The last, and probably most important question, you have to ask yourself is: How often will I be you'll be using it?
While we should all aim to make the healthiest choices as often as possible, variety is good. Fat is an important part of any diet, so as long as you stick to the recommended general guideline of keeping your intake below 30%* and picking the higher MUFA and lower SFA options most of the time, you should be good. If you however already have a chronic disease or high cholesterol, talk with your doctor or dietician on the safest options.
For healthy individuals: Butter and coconut oil wil not have you instantly keel over, and using extra virgin olive to sear your meat that one time because you don't have anything else won't result in unsurmountable free radical attack. Just don't overdo it.
*On a 8000 kJ diet, this is about 2400 kJ from fat, which translates to about 65g of fat (or about 4,5 tablespoons of oil) per day. But remember that nuts, meat and other food also contain fat, so you can see why it's easy to overshoot on your intake!