Unfortunately, the very short answer to this question turns out to be a very frustrating, "yes and no." While research studies on olive oil cooking show fairly consistent results, it is possible to interpret the study findings as both supportive and non-supportive of olive oil cooking. In this article, we'll take you through the quick basics you need to know when deciding about the olive oil and cooking approach you want to take. At WHFoods, we have decided that the use of EVOO in cooking is not the best option for health. But we also want you to know how we arrived at our decision, so that you can weigh the pros and cons and decide for yourself.

No Study Gives Heated Oil a "Green Light"

At the very outset, we feel confident in telling you that no research study gives a "green light" for the use of EVOO in cooking. In fact, the most comprehensive review studies in this area show that certain desirable features in EVOO can be quickly lost through cooking. For persons deciding to use EVOO in cooking, some studies specifically recommend that this oil only be added close to the end of the cooking process.

In the public press, there has been a good bit of confusion over EVOO and cooking, because studies also show that EVOO has some preferable cooking characteristics in comparison to other oils. In other words, if you have already decided to cook with a plant oil, there are some definite advantages to EVOO versus other plant oils. For example, a key feature of EVOO is its high monounsaturated fatty acid (MUFA) content. EVOO gets a reasonable amount of "thermal resistance" (protection from breakdown by heat) from its high MUFA content. Studies show that the overall degradation of EVOO by heat is less than many other cooking oils, including sunflower oil, high-oleic sunflower oil, canola, and peanut oil. So with respect to cooking oil comparisons, the studies show that cooking with EVOO may be better than cooking with these other oils.

However, these research comparisons between EVOO and other cooking oils do not address the question, "Should you be cooking with any oil at all?" In other words, while these studies show some advantages to cooking with EVOO versus other oils, they do not examine the issue of whether a person might be better off if all the use of all oils, including EVOO, during cooking was avoided. And these comparison studies do not address possible benefits from consumption of EVOO in its uncooked versus cooked form.

The Confusion Surrounding Smoke Point

Judging from internet website information and discussions in public media, smoke point is one of the most confusing issues related to oils and cooking. All cooking oils have some smoke point. Typically, this smoke point falls between 200°-500°F (93°-260°C). Smoke point is not defined as the moment when a heated oil first begins to smoke. It's defined as the moment when a heated oil begins to smoke continuously. The moment when an oil starts to smoke continuously corresponds to the moment in time when its fat molecules start to break down at a much faster rate. (In chemical terms, the breakdown of triacylglocerols, or TAGs, into glycerol and free fatty acids starts to proceed at a much more rapid rate beginning at smoke point.) As the breakdown of fat molecules speeds up, additional problematic by-products are formed. For example, once smoke point has been exceeded, more glycerol molecules get converted into acrolein, a substance that can bring along with it unwanted health risks if we end up with overexposure to it. At WHFoods, we are not aware of any studies that recommend going beyond an oil's smoke point, and we recommend staying below smoke point as a general cooking practice if oils are used during cooking. However, the relationship between oils and smoke point is not as straightforward as many people might think, and we believe that optimal health requires more than simply cooking below smoke point. In the next section, we will explain why it is not enough to simply stay below smoke point.

What Causes a Cooking Oil to Smoke?

The direct answer to this question is "numerous factors." And this is one place where you will need to exercise some caution in reading many website reports. For example, you will find some website articles focusing on the amount of saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), and polyunsaturated fatty acids (PUFA) in an oil as the key factor when determining its smoke point. Research studies do not support this point of view. The balance between SFA-MUFA-PUFA definitely has an impact on smoke point, but a more important contributing factor is the length of the fatty acids themselves. Fatty acid size is measured by "chain length," which is shorthand for the number of carbon atoms linked together in a chain. Let's take the example of EVOO and coconut oil. EVOO contains far more PUFA than coconut oil, and based on this characteristic, you might expect it to have a lower smoke point due to a greater risk of PUFA oxidation. However, coconut oil actually has the lower smoke point than EVOO—347°F (175°C) versus 383°F (195°C). One important reason involves the lack of short chain fatty acids in EVOO, and the unusually large number of short chain fatty acids in coconut oil. So as you can see, it can be a mistake to jump to conclusions about oils and their smoke points.

How Does the Smoke Point of EVOO Compare with Other Oils?

A recent research study in this area lists the following four cooking oils and their smoke points:

• Coconut oil: 347°F (175°C)
• EVOO: 383°F (195°C)
• Safflower oil: 414°F (212°C)
• Canola oil: 460°F (238°C)

You will notice that EVOO falls into a "middle" range in terms of smoke point, and as a general rule, we believe that "middle range" is a good way of describing the smoke point of EVOO in comparison to other oils. However, information above only shows the relationship between smoke point and type of oil. Missing from the chart, however, is a second type of information that is always just as important—and sometimes more important—than type of oil. That information involves steps that were taken during the processing of the oil.

While all oils have been processed in some way, many are also processed to make them more "refined." Refining is a process that typically involves removal of numerous substances (including nutrients) from the oil. For example, free fatty acids, gums, and color pigments are frequently reduced during refinement. In the case of olive oil, refining is sometimes used to lower the acidity of the oil and make it palatable for consumption from a taste standpoint. Refinement of oils also raises their smoke points and frees them up for a longer shelf life and for use with a wider range of cooking heats. It is often possible to nearly double the smoke point of an oil through the refining process. A canola oil that started out unrefined with a smoke point of 225°F (107°C) might end up with a smoke point of 400°-460°C after full refinement. Similarly, sunflower and safflower oils that stated out with smoke points of 225°F (107°C) might have their smoke points raised to 450°F (232°C) after being refined. (In the smoke point values presented above, we suspect that the coconut oil and EVOO were less refined than the safflower and canola oil, although the study authors did not specify the refinement status of their oils.)

Why We Don't Recommend Refined Olive Oil

Particularly in the case of EVOO, refinement is a step that does not make sense to us from a health standpoint. Because refinement typically results in a loss of nutrients—including color pigments that have antioxidant and anti-inflammatory health benefits—we believe that refinement causes you to lose some of the very benefits that prompted you to choose EVOO in the first place! You can much more easily stay below smoke point if you choose the refined version of an oil (including olive oil) —but from our perspective, that approach does not make sense, because it will cause you to lose too many desirable nutrients. In other words, we believe that the trade-off between high smoke point and less nutrients is not a good trade off, especially in the case of EVOO, which offers such outstanding phytonutrient richness.

Even Below Smoke Point, Nutrients Can Be Lost

As you can see from the previous section, refinement is a process that can result in a loss of valuable nutrients, even if an oil is never used in cooking. In other words, refinement is a great example of lost quality in an oil that was not caused by exceeding its smoke point! In this context, what we also want you to know is that the nutritional richness of EVOO can be comprised when EVOO is used in cooking, even if the cooking temperature stays below the smoke point of EVOO. For example, we've seen one study that showed loss of vitamin E in olive oil after one minute of microwaving at 1000W (watts). We've also seen a study that showed a 14% reduction in oleuropein—a key anti-inflammatory phytonutrient in EVOO—after one hour of heating at 176°F (80°C). And we have seen numerous studies showing 5-15% loss of various phytonutrients following the use of EVOO in cooking, even when the cooking temperature remained below smoke point. Interestingly, in one study, loss of the phenolic antioxidant oleocanthal from EVOO during cooking was a loss that study participants were able to detect in terms of taste, even when the cooking temperature stayed below smoke point.

Specific WHFoods Recommendations

For some people, a 5-15% loss of various phytonutrients associated with the heating of EVOO below smoke point might not seem like a valid reason for removing EVOO from the cooking process. This percentage might simply seem too low, and the problems with exceeding smoke point could obviously be avoided by keeping the cooking temperature below it. For other persons who decide that they want to cook with an oil no matter what, EVOO might make a good choice in comparison to other cooking oils. But at WHFoods, we believe that the potential loss of 5-15% loss of anti-inflammatory and antioxidant nutrients is worth avoiding in the use of EVOO, especially when there are simple and delicious ways to incorporate EVOO into your meal plan without subjecting it to cooking heats. We always recommend staying below smoke point. But we do not think it is worth the nutrient loss to stay below smoke point by purchasing a refined oil. For some great recipes that include EVOO without subjecting it to cooking heats, just visit our Recipe Assistant and select "olive oil" in our "Foods to Include" menu.

References

• Attya M, Benabdelkamel H, Perri E, et al. Effects of conventional heating on the stability of major olive oil phenolic compounds by tandem mass spectrometry and isotope dilution assay. Molecules. 2010 Dec 1;15(12):8734-46.
• Cicerale S, Conlan XA, Barnett NW, et al. Influence of heat on biological activity and concentration of oleocanthal--a natural anti-inflammatory agent in virgin olive oil. J Agric Food Chem 2009;57:1326-30.