Mediterranean cultures have been frying food in olive oil for all of recorded history. Only recently, however, have modern nutritionists discovered the health benefits of olive oil and the possible health effects of heating olive oil to frying temperatures. Heating olive oil decreases the nutritional value of the oil. It does not, however, make the oil unhealthy, unless the oil is heated past its smoke point.
Monounsaturated Fats
Olive oil is rich in monounsaturated fatty acids, or MUFAs. According to Donald Hensrud, M.D., of the Mayo Clinic, MUFAs lower cholesterol levels, especially the dangerous low-density lipoprotein cholesterol levels in the blood. They help normalize blood clotting and also help regulate blood sugar. Consequently, they might help lower your risk of heart disease and coronary artery disease. The MUFAs in olive oil will not change into another kind of fatty acid when the oil is heated, so olive oil used for frying retains the benefits of MUFAs.
Evaporation of Esters
Olive oil may, however, lose some of its other nutritional benefits when heated. According to the Olive Oil Source, heat evaporates the alcohols and esters in olive oil. Consequently, the delicate smell and taste of olive oil diminishes when the oil is heated. But these esters are not just fragrance. They also have health benefits. Syed Haris Omar, a researcher from the Qassim University College of Pharmacy, has discovered that oleuropein, one of the esters in olive oil, has antioxidant, anti-inflammatory and possibly anti-cancer benefits. Heating olive oil to the point where these esters evaporate will reduce those benefits.
Smoke Point
The biggest health risk when frying with olive oil occurs when it is heated beyond its smoke point. The smoke point of an oil is the temperature at which the oil begins to give off smoke. That smoke contains compounds harmful to human health. Some of these compounds are harmful when breathed in along with the smoke. Others, free radicals, have been implicated in degenerative diseases like cancer.
Varieties of Olive Oil
Olive oil has a wide range of smoke points. Extra virgin olive oil smokes at 320 degrees Fahrenheit. A high-quality low-acidity extra virgin oil smokes at 405 degrees. Virgin olive oil smokes at 420 degrees and extra light olive oil smokes at 468 degrees. Foods are typically fried at 350 to 375 degrees. Practically, that means that some olive oils are fine for frying; others will smoke before getting hot enough to fry well. Choosing a low-acid, light oil will minimize the health hazards of frying in olive oil.
References
- Scientia Pharmaceutiica; Oleuropein in Olive and its Pharmacological Effects; Syed Haris Omar; April 2010
- Mayo Clinic; Olive Oil: What Are The Health Benefits?; Donald Hensrud; March 2011
- The Olive Oil Source: The Basics
- The Olive Oil Source: Heating Olive Oil
- Cooking for Engineers; Smoke Points of Various Fats; Michael Chu; June 2004
- Journal of Agricultural and Food Chemistry; Comparison of Volatile Aldehydes Present in the Cooking Fumes of Extra Virgin Olive, Olive, and Canola Oils; A Fullana, et al.; August 2004
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