Olive oil has become very popular since it was found that the Mediterranean diet is one of the healthiest ones, and this oil is an integral part of it. Despite its benefits, which are numerous and reported by many a scientist, the question still stands: is it a good oil to fry in?
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A controversial question
Oils change their properties when heated, especially if the temperature is very high: it can change its taste and smell, but there are changes that are more difficult to detect. The chemical compounds that result from heating oil can be harmful, and olive oil (it is oil after all!) is no exception.
The most important chemical changes occur when oil is heated above the smoke point, i.e. when the oil is burnt. Vegetable oils produce toxic chemicals when heated, and these are called aldehydes. Despite the fact that the chemical is found in many natural sources and even formed in humans, consuming aldehydes is associated with increased risk for heart disease and diabetes. Olive oil belongs to the category of vegetable oils, so it also produces these substances when heated.
Does it mean that animal fats should be preferred over vegetable oils?
No easy answer
As far as olive oil is concerned, it is very difficult to find an unambiguous answer. There are several reasons for that.
On the one hand, researchers reported that some vegetable oils produce 20 times more aldehydes than the level recommended by the WHO, and these two types are, surprisingly, sunflower and corn oils. Olive oil is not among them: it showed much better results by producing way less aldehydes. On the other hand, goose fat and lard, which have the reputation of being unhealthy, did the same.
Lard is rich in monounsaturated fats, which makes it a good candidate for frying in it, as these are more stable when heated, and saturated fats are even better at enduring high temperatures. That is why it’s still a controversial issue whether vegetable oils are a healthier option.
The key to finding the most optimal oil to fry in seems to be the following: the less polyunsaturated fats there are in oil, the better; and, vice versa, frying in oils rich in saturated and monounsaturated lipids is recommended. According to Prof M. Grootveld, the best oil for frying must contain no more than 20% polyunsaturates and more than 80% saturated and monounsaturated fats (with the share of one of them making up more than 60%). That being said, olive oil is a good candidate: there are only 10% polyunsaturates, 76% monounsaturates and 14% saturates.
So, frying in olive oil does not appear to be the perfect way to do it, but it is not the worst choice: actually, it is one of the best options there are, especially if we take into account huge amounts of aldehydes produced by sunflower and corn oils and disadvantages of other kinds of oil and fat.
Is extra-virgin olive oil the best olive oil to fry in?
Opinions differ when it comes to whether extra-virgin oil should be preferred. The above mentioned Prof Grootveld says the levels of antioxidants in such oils are not enough to protect them from oxidation.
R. Adams from Cardiff Metropolitan University says that the quality of olive oil matters, as the higher the smoke point, which increases with the oil quality, the less dangerous the oil becomes, because such oils contain more antioxidants and less free fatty acids.
It seems like olive oil is still the best option to choose when finding a good kind of oil to fry in. Frying is not the healthiest way of cooking, and it is recommended to avoid frying at all, but if you do, choosing olive oil can be a good idea. Just make sure the temperature is not too high, and the amount of oil used is not large.
Aldehyde Sources, Metabolism, Molecular Toxicity Mechanisms, and Possible Effects on Human Health –Tandfonline.com
DMU research on ‘healthiest’ cooking oils revealed on BBC’s Trust Me, I’m a Doctor – Dmu.ac.uk
Which oils are best to cook with? – BBC.com