Olives are one of the oldest foods known to man and are thought to have originated in Crete or Syria some 6000 years ago. The golden color of the rich oil pressed from tree ripened olives has been consumed by healthy traditional cultures since as early as 3000 BC. Olive oil is truly one of the crown jewels of fats!
Olive oil is primarily composed of oleic acid, which is a monounsaturated fat. Monounsaturates are one of three main categories of fats. The other two are saturated fats and polyunsaturated oils.
The three types of fats – do you know how to tell the difference?
Saturated fats like coconut oil and tallow, are extremely stable because they pack together tightly courtesy of very straight carbon bonds that are all occupied by hydrogen atoms. Saturated fats are solid or semisolid at room temperature and make ideal cooking fats because of the inherent stability provided by their chemical structure which means that they do not easily go rancid when heated during cooking or form the free radicals that contribute to heart disease and cancer.
Polyunsaturated fats do not pack together as tightly as saturated fats and hence are liquid at room temperature and remain so even if refrigerated. The chemical structure of polyunsaturated oils is such that there are unpaired electrons for every carbon-carbon double bond which are highly reactive if heated or processed in any way. Even simple exposure to the air or light can cause rancidity in fairly short periods of time.
Monounsaturated fats like olive, sesame, and avocado oil are liquid at room temperature yet become solid if refrigerated. The single carbon-carbon double bonds which make up the chemical structure of monounsaturated fats do not pack together as tightly as saturated fats but are more tightly bound than those of polyunsaturated oils.
Monounsaturated fats do not go rancid as easily as polyunsaturated oils but are more delicate than saturated fats due to a slight molecular bend which is not as straight in shape as the carbon bonds in a fully saturated molecule.
Now that we understand the basic structure of the 3 types of fats, it is easy to identify the type of fat that primarily composes an oil as this can be ascertained by simply observing its form at either room temperature or when refrigerated.
If a natural fat is solid or semisolid at room temperature, then it is primarily saturated. If it is fully liquid at room temperature but goes solid in the refrigerator, it is primarily monounsaturated, and if it is liquid when either refrigerated or at room temperature, it is mostly polyunsaturated.
With proper identification of the kinds of fats now complete, let’s turn our attention to the proper cooking oils.
Cooking with what fats - when?
It is clear that fats that are primarily saturated like tallow, coconut or palm oils are wonderful for cooking as the heat from cooking does not easily damage them or form free radicals.
On the other hand, polyunsaturated oils like sunflower, corn, soy or safflower should be strictly avoided for cooking as they are too easily damaged as those free electrons react too easily with heat or oxygen.
But what about monounsaturated fats, in particular olive oil? This is where the issue gets a bit murky.
It is absolutely true that cooking with olive oil will not form transfats. Even higher heat cooking with olive oil will not cause much free radical creation although I would venture to say that there are certainly some free radicals formed when high heat cooking with monounsaturates due to the slightly less stable structure as compared with saturated fats.
I personally choose to avoid cooking with olive oil, especially extra virgin olive oil (EVOO). For one thing, good quality EVOO is quite expensive and should be properly packaged in dark colored glass to protect the delicate nutrients. Studies have shown that light quickly degrades the quality of extra virgin olive oil. Research published in New Scientist magazine showed only two months exposure to light caused free radical increases in extra virgin olive oil to such a level that it could no longer be classified as extra virgin!
With light so easily damaging to extra virgin olive oil, it seems obvious that heat would damage it as well and studies bear this out. Heat as low as 350F (180C) can significantly damage the beneficial phenols in olive oil. Phenolic substances are highly anti-inflammatory in nature and likely an important reason why studies of the Mediterranean Diet which is high in olive oil have indicated a decrease in heart disease risk.
As a result, it seems prudent that even though cooking with olive oil does not produce any transfats or much free radical damage, it does reduce much of the beneficial aspect of consuming this healthy traditional oil in the first place.
Light sautes using olive oil at temperatures no higher than 200-250F seem to be safe and minimally damaging, but oven baking or higher heat cooking on the stovetop with olive oil is not wise given that there are much hardier and less expensive fats to choose from like expeller pressed coconut oil or palm oil!
By far, the best use of good quality, nutrient loaded extra virgin olive oil is as a salad dressing. Combining one part vinegar or lemon juice with between 3-5 parts oil along with a drizzle of walnut oil and flavoring herbs of choice will provide a truly healthy topping for any salad or vegetable mix.
A Word of Caution for Olive Oil Lovers
While numerous studies have shown the beneficial effect of olive oil in the diet likely due to the anti-inflammatory nature of the phenols, it is advisable to go easy on this traditional fat if weight loss is your goal.
In 1994, the journal The Lancet published a study which noted that fat tissue is primarily composed of monounsaturated fat. Could this be a contributing reason for middle age weight gain that is so common in Mediterranean countries (Eat Fat Lose Fat, p.70)?
The chemical structure of monounsaturated oils could be part of the problem. Monounsaturates like those found in olive oil are composed of longer chain fatty acids unlike the short and medium chain fatty acids found in coconut oil, palm oil, butter and other animal fats. Short and medium chain fatty acids are absorbed quickly and directly by the body for immediate energy whereas the longer chain fatty acids must be acted upon by bile salts to be digested. For this reason, longer chain fatty acids are more likely to contribute to weight gain.
Where to Find Quality Extra Virgin Olive Oil
It is important to realize that much of the conventional olive oil on the market isn’t even olive oil at all, according to Tim Mueller, an investigative journalist who has written a book on the subject. If you suspect your olive oil is fake, put it in the refrigerator to see if it properly solidifies. Another test is to see if your extra virgin olive oil can keep a wick burning. Refined oils masquerading as extra virgin olive oil cannot hold a flame.
Unfortunately, neither of these tests can completely guarantee authenticity. To be sure of the quality of your extra virgin olive oil, click here for a list of vetted sources that I trust and buy from myself.
Sarah, The Healthy Home Economist