By Chloe Warren
When it comes to "fats" it can be difficult to pick apart fact from fiction.
Coconut oil promotes weight loss (unlikely). Butter protects against cancer (not exactly). Eating fats makes you fat (oh, dear).
For decades we were warned off all fats, but now it's clear that some of them are an essential component in a healthy diet.
Fats, oils and how much you need
We all need a certain amount of fat in our diet. It gives us energy, stops us from feeling hungry, keeps us warm and our organs safe, and our bodies use fatty acids to produce hormones and neurotransmitters (chemical messengers), and to absorb some vitamins.
Fats can also affect your blood cholesterol level (we'll come back to this later).
But when it comes to fat, you can definitely have too much of a good thing. This is because fat has a very high energy density, which means gram for gram it contains more kilojoules than say carbohydrates or protein.
Dietary guidelines right across the world recommend we limit our fat intake to ensure we don't end up consuming more kilojoules than we need.
The Australian guidelines say "it is important to eat unsaturated fats in small amounts as part of a balanced diet", and recommend that no more than 20 to 35 per cent of our kilojoules come from fats — that's because we need to fit in all our other daily nutrients, too.
None of this means that all fats are necessarily a bad thing. Just that you shouldn't have too much of them.
Types of fats (not all are created equal)
The other reason fats tend to be controversial is that some fats are better for us than others.
So where should you get your fats from? Ideally, from foods that contain healthy fats, otherwise known as unsaturated fats, of which there are two distinct types: monounsaturated and polyunsaturated fats.
Unsaturated fats don't have quite the same reputation as other fats: in fact, they can improve blood cholesterol levels when they replace saturated fats in our diet.
Foods containing unsaturated fats include nuts, avocados, seafood, and oils made from some plants or seeds.
The other fats fall into two broad categories. We're generally encouraged to limit how often we have these:
Saturated fats are mostly found in animal products (butter, cheese, milk, lard) and coconut oil. It's recommended you limit your intake of these types of fats and replace with unsaturated fats where possible. This is because research has linked these fats with increased risk of cardiovascular disease.
But if we're really looking to identify some villains when it comes to fats, then it's the trans fats that are the bad guys.
Trans fats have no known health benefits and are linked to heart disease. They naturally occur in some animal products, but they are also present in processed foods due to the way fats and oils change throughout the manufacturing process.
The good oil
And as far as fats go, reputations don't come much richer than that of the beloved olive oil.
There is a lot of evidence that shows olive oil is the ideal way to get the right kind of fats into your diet.
In part it's because olive oil is a source of unsaturated fat, but there is also plenty of evidence for many other health benefits which come from olive oil, too. You might read about polynutrients, or antioxidants, or even antibiotic properties.
But there are some interesting reasons why there is so much evidence about the health benefits of olive oil.
"We're always restricted to being able to report on the research that exists," explains Professor Amanda Lee of the University of Queensland School of Public Health.
"A lot of these studies that are reported to be about olive oil aren't about olive oil at all, but about the Mediterranean diet — that does include olive oil — but it's also rich in fruits, vegetables, whole grains and fish. That diet has been shown to decrease the risk of cardiovascular disease and some cancers, but olive oil is only one component."
As far as fats go, the fact remains that olive oil is a great way to work the right ones into your diet, even if the precise health benefits and the mechanisms through which they are provided are debatable.
Choosing the right olive oil
If you've purchased olive oil before (hurrah!), you've probably noticed the drastic differences in pricing between all the varieties.
Extra virgin is the most expensive, and for good reason.
"Extra virgin olive oil is produced from the first pressing of the olives, without any heat," explains Rosemary Stanton, nutritionist and visiting fellow with UNSW.
This is contrast to 'virgin', 'light', or 'pure' olive oils, which are made with some use of heat, or might be mixed in with other oils or solvents. This heat can destroy some of the nutrients that come naturally from the olive fruit.
Nutritionists also recommend that locally-sourced extra virgin olive oil is best: all oils oxidise over time, and this changes the nature of the oil away from being unsaturated to more saturated.
"You can smell if an oil is getting oxidised," explains Professor Lee. "It becomes rancid when it produces those short-chain fatty acids, and it's not a nice taste."
This shifty nature of the oil also means that it can't be stored for too long (12 months at the most, and away from sunlight, please!).
"It's a seasonal product," says Dr Stanton. "There's a new crop every year and that's the one you should be going for. We actually do the judging for olive oils for the Royal Easter Show in September, because the fresher the olives are, the higher the levels of all those nutrients you can taste."
The smoke point debate
While we know that olive oil is a "good oil", there is still some disagreement about when it is best to use in cooking.
All this discussion is around its smoke point: the temperature at which it burns. Once an oil burns it can produce harmful chemicals, and it also tastes and smells pretty awful.
"All those health benefits aren't maintained once olive oil starts burning," says Professor Lee.
Generally, the higher the quality of the olive oil, the higher its smoke point.
"As long as it's fresh," explains Dr Stanton. "That is the clue to everything about olive oil — that it needs to be fresh."
Of course, frying generally isn't the healthiest way to cook food anyway.
While extra virgin olive oil is technically the healthiest type of olive oil, it's also the most expensive.
This is another reason why it might not be appropriate to use it for methods of cooking where you would require a high volume of oil, like deep-frying.
If you're using it as your main source of fats, then a couple of tablespoons per meal is an adequate serving size — but it really comes down to personal choice (and the size of your wallet) as to whether you'd prioritise it over a cheaper olive oil.
Source: ABC Life