Is It Really Safe to Cook with Olive Oil?

Olive oil is known for its health benefits, however many Paleo experts say we should not be cooking with it. Does olive oil stand until the heat?

Olive oil has always been a nourishment saint. Its health benefits have been touted for ages -- high in antioxidants, anti-inflammatory, anti-cancer...the list continues. Even the USDA agrees the stuff is great for our health!

Nevertheless there's a popular myth circulating in the Paleo community that it's unsafe to cook with olive oil; that it isn't stable and oxidizes when heated, forming harmful by-products in the process.

Even though this is accurate for other oils such as canola and vegetable oil, I'm here to tell you that it's okay to cook with olive oil. It has some special qualities that make it stable under cooking conditions, and given you are buying premium quality olive oil to start with, you can sauté for a heart's content.

What Is Fat Oxidation?

There are three different types of fatty acids: saturated, monounsaturated, and polyunsaturated. What defines them is their arrangement; a saturated fat has zero double bonds (hence it is"saturated" with hydrogen), while a monounsaturated fatty acid has one double bond, and a polyunsaturated fatty acid has greater than one. Have a look at the diagrams below and note that the saturated fatty acid (left) has no double bonds, whereas monounsaturated fatty acid (center) and polyunsaturated fatty acid (right) have you and 2, respectively. The double bonds are the "kinks" in the chain.


Double bonds are unstable when they are in contact with a number of components, such as light, heat, and oxygen. While we call certain fats"saturated" or"monounsaturated," the truth is that the fats we all cook with are made up of many different sorts of fatty acids and we refer to them with their majority.

For example, coconut oil (what we call a saturated fat) is made of 90% saturated fat. This differs from butter (another saturated fat), which has just 60% saturated fatty acids, the remainder of it's monounsaturated and polyunsaturated fat. Soybean oil, on the other hand, is about 60% polyunsaturated fats. All of these differ from olive oil, that is made up of 70% oleic acid, a monounsaturated fat.

Because polyunsaturated fats have the maximum double bonds of all the fatty acids, they are more vulnerable to oxidation. When polyunsaturated fatty acids oxidize they form unhealthy molecules called advanced lipid oxidation end products (ALEs).

These ALEs cause an inflammatory reaction in the circulatory system, as well as the liver, kidney, lungs, and gut, and are believed to have negative impacts on human health. This is why a Paleo diet excludes dietary fats with high percentages of polyunsaturated fats.

Why Olive Oil Is Less Prone to Oxidation

There are just two reasons why olive oil outperforms other vegetable oils when it is heated. Firstit contains polyphenols and tocopherols which act to defend the oil from oxidation. Second, it's made up of mainly monounsaturated fat -- remember, that's the one with just one double bond, which makes it more stable in heat than fats with high amounts of polyunsaturated fats which have more double bonds. Between these two properties, olive oil can fry together with the very best of them.

It is thought that the phenolic compounds in olive oil -- polyphenols and tocopherols -- may influence olive oil's stability in heat even more than its monounsaturated fat material. The phenolic compounds donate a radical hydrogen into alkylperoxyl radicals to form a stabilized radical. For the chemistry buffs out there, this reaction works like this: ROO• + AH → ROOH + A•

One study fried olive oil varieties to find out how they stood up to high heat, and only after 24-27 hours of frying (depending upon the kind ) were they believed to be harmful. Vegetable oil, on the other hand, was only able to really go for 15 hours.

Despite lower amounts of vitamin E, olive oil ended up less oxidized than the vegetable oil. The researchers also found that the polyphenol content of olive oil predicted its susceptibility to oxidation; varieties with much more polyphenols were less prone to oxidation while those with less became more oxidized.

Other researchers heated extra virgin olive oil to 350°F for 36 hours (yes, you read that properly. 36 hours!) And found that while there was some degradation in the phenolic compounds content, the oil kept nearly all of its nutritional value. Considering that the average home cook will never cook anything for 36 hours straight, I believe we are pretty safe here.

Another study compared insulin sensitivity in obese, insulin-resistant girls when they have foods fried in extra virgin olive oil into meals that contained olive oil. This one surprised me as it compared the cooked vs. raw olive oil, and cooked won out.

There was no difference in insulin sensitivity when the oils were eaten by lean subjects, however. This was a small study, but it's intriguing to hear that perhaps the cooked olive oil may have some benefits over raw oil for some people.

Being able to heat olive oil opens up cooking alternatives, especially for people who are very sensitive to the effects of saturated fat in their own cholesterol levels.

If you've been hanging around for a while, you probably know that your cholesterol levels aren't the end-all-be-all. But, people who have familial hypercholesterolemia (and even those without!) Will be happy to hear that they can cook with a fat that has been shown to decrease LDL oxidation, thus improving their heart health.

How to Buy and Store Olive Oil

Though the fact that olive oil contains mostly monounsaturated fatty acids is important, researchers believe that it is actually the phenolic compounds that stabilize the oil as it's heated. This is the reason it's vital that you purchase extra-virgin olive oil versus pure olive oil. Extra-virgin olive oil goes through less processing -- it is simply pressed and does not go under any heat or chemical treatment.

Olive oil is one of the only oils that Americans still consume relatively unprocessed; many of the oils we buy are refined. Pressing the olives retains many more nutrients, including phenolic compounds, which we all know function to safeguard olive oil from heat. Better is extra-virgin olive oil that hasn't been filtered -- the particles that cause the oil to become muddy also act as antioxidants and buffers against acidity, therefore protecting the oil from oxidation. (4)

That said, much of the extra-virgin olive oil bought in the United States is adulterated with other oils such as soybean or rapeseed. That's a bummer considering that many of us prefer to purchase our olive oil when we visit the grocery store.

Thankfully, olive oil expert Tom Mueller has a list of extra-virgin olive oils you can buy at your local grocery store (including the real deal from chains like Costco, Trader Joes and Whole Foods). Make sure to test that out and if you'd like to learn more about this issue, read Mueller's book Extra Virginity: The Sublime and Scandalous World of Olive Oil.

The other alternative, of course, is always to source your olive oil from a company you trust. If you live in a climate that affirms olive growth, you may even be able to find a local company to purchase from.

If not, there are a plethora of options online, and it simply becomes a matter of researching the company and preferably talking to a representative to see how they process the oil.

Once you've got your hands on a quality extra-virgin olive oil, take care to keep it correctly. Remember that heat is only one of the elements that causes fatty acid oxidation, the others being light and oxygen.
You should keep your olive oil in a cool, dark place in a dark airtight container.

(Don't purchase olive oil that comes in a clear container, especially if you suspect it has been sitting on the shelf for a little while.) If you purchase large tins of olive oil, pour out what you'll use in a few weeks into another dark jar so that you can avoid opening the tin often and exposing the oil into oxygen.

Here's the bottom line: extra-virgin olive oil is perfectly safe to cook with. It stands up well to heat owing to its monunsaturated fatty acid and phenolic compounds material and fares much better than other vegetable oils. It is a great oil to eat both in taste and health and should not be avoided. However, it's not the sole healthy fat out there! You should always eat a variety of healthy foodsfats contained.