Celebrity chefs do it. Mediterranean households do it. And now, researchers from top-notch universities are recommending you do it. Wondering what “it” is? We’re talking about cooking with olive oil. And we don’t just mean using this versatile oil in cold preparations or as a finisher. We mean sautéing, grilling, roasting, baking – and yes – frying with it. For a while now, the word on the street has been that heating olive oil destroys its nutritional value and, in addition, creates toxic by-products. The growing body of scientific research on the subject, however, seems to be saying something different. While all cooking oils can oxidize or deteriorate when exposed to oxygen, light and heat, extra-virgin olive oil (EVOO) has an impressive array of nutritional benefits and built-in defense mechanisms that actually make it a truly healthy, as well as delicious, choice for all types of cooking. What’s more, study after study indicates EVOO’s smoke point is actually well within the range needed for high-heat applications like frying. So, although it’s true the nutritional value of many foods is diminished when exposed to heat, unless you enjoy eating your three-squares-a-day raw, cooking in olive oil might be the next best thing.
Olive Oil is a “Good” Fat
Understanding the effects of heat on EVOO begins with understanding the mechanics of this superfood’s nutritional arsenal. All cooking oils are comprised of fatty acids, which our bodies need to boost cellular, brain, and nerve function, generate and store energy, regulate bodily processes, promote healthy tissues, and transport vitamins. But not all fats are created equal. There are the “good” fats, such as the polyunsaturated fats found in seeds, nuts and seafood and the monounsaturated fats found in olives and avocados. These promote brain function and cellular growth, while also lowering cholesterol levels and the risk of heart disease. And then, there are the less reputable saturated fats we’ve been warned about. Found in animal products, such as butter, and a mainstay of the creamy comfort foods we love, rich, melt-in-your-mouth saturated fats should be used sparingly if we want to keep our cholesterol levels in check and avoid the possibility of an untimely heart attack. Truth be told though; most oils are a mix of all three types of fatty acids. The higher the percentage of polyunsaturated and monounsaturated fatty acids an oil has relative to the percentage of saturated fatty acids, the more health benefits it can deliver. Monounsaturated fat, especially, is well-suited to stove-top and oven cooking because its molecular structure is more stable than that of polyunsaturated fat and, therefore, less likely to degrade when heated. Olive oil’s reputation as a healthy oil stems from the fact that roughly 85%1 of its fatty acids fall into the unsaturated camp, with the bulk being relatively stable monounsaturated fats. So, when in doubt about which type of oil to use in your cooking, just remember unsaturated fats (olive oil) – good; saturated fats (butter) – not-so-much!
Phenols in Olive Oil Pack a Powerful Punch
Although olive oil gets a considerable amount of street cred for being a healthy monounsaturated fat composed mostly of oleic acid, a nutrient that fights inflammation, the real secret behind olive oil’s (and especially EVOO’s) nutritious profile is its high phenol content. Phenols are naturally occurring compounds found in plants that protect against the sun’s rays, pathogens, oxidative damage and harsh weather. EVOO’s extraction process, which is done without chemicals and with only minimal heat, allows it to retain significantly higher levels of phenols than are found in more refined oils. In our diet, these phenolic compounds become micronutrients packed with antioxidants, such as Vitamin E and oleocanthal. Vitamin E helps prevent cell damage caused by free radicals, overreactive molecules that have been linked to cancer. And oleocanthal reduces the risk of inflammatory diseases, such as heart disease. You know phenols are present when, after sampling an oil, you feel an oddly pleasant tingling in the back of your throat. Phenols are the components of an oil that add a sharp, pucker-worthy bite to foods and cause us to think of an oil as bitter or pungent – but in a yummy kind of way! Credited with being both anti-inflammatory agents and antioxidants, phenols fight diseases related to aging, including arthritis, osteoporosis, heart disease, high blood pressure, high cholesterol, cancer and stroke.
EVOO Retains Nutritional Benefits Even When Heated
Based on the information above, the jury appears to be in; EVOO, with its treasure trove of oleic acid and antioxidants, is definitely good for us. The trickier question is can we capture that goodness regardless of whether we’re sautéing, frying or roasting with EVOO or just slurping it right out of the bottle. The answer is a qualified “yes.” First, it’s important to acknowledge that, when heated beyond their smoke points, all oils will eventually oxidize (deteriorate), potentially releasing free radicals, those cancer-causing compounds we referred to earlier. Smoke points, the temperatures at which oils begin to smoke and break down, can vary by type of oil, varietal, age, field conditions, time of harvest, refinement level, fatty acid composition, or even by the surface area covered in the pan. For the most part though, any oil with a smoke point above 400oF is considered to have a smoke point high enough for the majority of home cooking techniques. Some polyunsaturated fats meet this criterion, for example soybean oil; however, due to their relatively loose and unstable molecular structures, polyunsaturated oils oxidize rapidly when overheated, potentially releasing more harmful compounds than do monounsaturated fats. This bodes well for making EVOO your go-to choice for stovetop and oven cooking. Not only is it loaded with a higher proportion of stable monounsaturated fats, it’s also loaded with antioxidants that actually help fat molecules resist oxidation. And given that most home roasting, sautéing, pan-frying and stir-frying is typically done between 250 and 400oF2, EVOO’s smoke point of about 400oF3 makes it a logical (and tasty) pick for most cooking techniques.
Not sold yet? Neither were we until our good friend and founder of Palo Alto-based Yummy Artisan Foods Mark Priestley convinced us to take a look at some of the published science on the topic. In addition to owning and operating Yummy Artisan Foods, a convenient and highly selective online source of award-winning foods, Mark is also an avid home chef and certified member of Applied Sensory’s tasting panel. As such, he has long been an advocate of cooking with EVOO, not only because it adds richness and complexity to the flavors in our foods, but also because research shows that even when exposed to heat, it is one of the healthiest, if not the healthiest, cooking oil available.
A 2017 study4 published in the Journal of the American Oil Chemists’ Society compared the thermal oxidation processes in several oils frequently recommended for frying. Potatoes were fried in EVOO, peanut oil and canola oil for six minutes. The process was repeated every 30 minutes for 30 hours, with volatile compounds being extracted from the used cooking oils at regular intervals and analyzed. The study’s conclusion was that EVOO has a greater resistance to oxidation during frying than both peanut oil and canola oil. Due to its higher percentage of stable, monounsaturated fatty acids versus unstable, polyunsaturated fatty acids and to its higher antioxidant content, EVOO was found to have degraded less and to have produced fewer toxic compounds at a slower rate than did the other oils.
A 2014 study5 published by the Journal of Agricultural and Food Chemistry fried potatoes at temperatures as high as 374oF using corn, soybean, sunflower, and olive oil. After reheating and reusing the oils multiple times, researchers concluded that the olive oil was the most stable and showed the greatest resistance to oxidation, while at the same time releasing the lowest amounts of harmful compounds.
A 2010 study6 published in Food Chemistry compared the suitability of different olive oils versus vegetable oil for use in home frying and found that the vegetable oil was much more susceptible to oxidation than were the olive oils. Oil samples were taken every three hours until the samples had degraded to unhealthy levels. Throughout the process, the EVOO sample, which began with a higher polyphenol content, displayed reduced levels of oxidation and higher levels of antioxidants, standing up to the heat for a full 27 hours. In comparison, the vegetable oil lasted only 15 hours.
A 2007 study7 published in the Journal of Agriculture and Food Chemistry evaluated the effects of heating two monovarietal EVOO samples to 356oF for 36 hours. Researchers continually monitored the oxidation progress by measuring oil quality changes, fatty acid composition and minor compound content. They concluded that despite the high temperature and lengthy cook time, both EVOO samples held onto most of their antioxidants and, consequently, most of their nutritional value.
The studies above are just a small subset of the available peer-reviewed research demonstrating that when it comes to safely frying foods, olive oil, and especially EVOO – due to its inherently high levels of oleic acid and antioxidants – outshines other popular choices, including vegetable, sunflower, soybean, canola, and corn oils. Not only does EVOO’s smoke point of about 400oF easily exceed ideal frying temperatures, EVOO resists degradation and holds onto its notable collection of nutrients over a longer period of time than do most other oils.
Granted, many believe that the best diet is one that consists of only whole, plant-based, uncooked or gently cooked foods. But if like us, you believe life is too short to forego cooking with fats entirely, then replacing your choice of saturated fat with a nutrient-laden, stable, unsaturated fat - like EVOO – is a good idea. And if adding the distinct, full-bodied flavor of a fresh, high quality EVOO to your fruits and veggies entices you to eat more of them, well that’s an even better reason to break out the EVOO!