Olive oil has been touted to consumers as the “heart-healthy” cooking fat since the introduction of the Mediterranean Diet in the late 1990’s. Purveyors of olive oils like to market the oil as having an ancient culinary legacy, however, as discussed in Part I of this series, this is actually just a marketing scheme to get people to use more olive oil in the kitchen. In Part II of this primer, we’ll discuss what you need to know about olive oil to be an informed consumer.
When choosing between extra virgin olive oil (EVOO), virgin olive oil (VOO), and simply olive oil, it’s best to go with EVOO, which is the least processed and most nutrient-dense of the three versions. While both EVOO and VOO are obtained using mechanical processing methods (i.e., they are not chemically refined), EVOO is the oil obtained from the first pressing of the olives, whereas VOO is from the second pressing. VOO has a lower nutrient content than EVOO (many of the nutrients are extracted during the first pressing), as well as lower quality standards for flavor, acidity, etc. Anything labeled simply ‘olive oil’ is obtained in a third round of extraction through a refining process that utilizes chemical solvents and heating to extract what little oil is left in the olives (Blalock, 2015). Nutrients are degraded during this industrial extraction process, and the oil’s fatty acids are damaged, yielding a product that is not highly recommended for consumption.
EVOO is brimming with antioxidants, vitamins, minerals, and other health-promoting compounds, many of which are heat-sensitive and degrade rapidly when exposed to heat, light, or oxygen. The presence of these substances, along with the fact that olive oil is a primarily monounsaturated fat, means that EVOO has a low smoke point at around 320 degrees Fahrenheit. The smoke point is the temperature at which glycerol (the molecule that forms the backbone of all lipids) is converted to acrolein, which is an aldehyde that creates the acrid smell and flavor in burnt oils (Blalock, 2015). Why should we be concerned about acrolein formation? Well, according to the NIH’s open chemistry database, PubChem, acrolein is “toxic to humans following inhalation, oral or dermal exposures.” Oxidative deterioration of unsaturated fats like olive oil upon heating are of concern for human health due to the fact that oxidative products and free radicals can damage DNA and cell membranes, and they are also implicated in the aging process and cancer growth (Naz, 2005). In addition, it is important to buy EVOO that is bottled in dark glass or other packaging that blocks out light, as exposure to light also hastens oxidation (Blalock, 2015).
The next time you go to buy olive oil, remember to purchase EVOO as this has the highest nutrient content, and to only use your olive oil cold (e.g. as a salad dressing or added on top of already cooked vegetables) in order to preserve heat-sensitive antioxidants and vitamins and to avoid ingestion of oxidized fats. When in need of a heat-stable cooking fat, opt for choices with a higher percentage of saturated fatty acids, which are significantly more resistant to oxidation (Naz, 2005). Good options for medium heat cooking include butter, ghee, lard, tallow, duck fat, and coconut oil.
Blalock, Bethany E. “How to Buy, Store and Eat Olive Oil.” Practical Gastroenterology 146th ser. (2015): 32-38. University of Virginia Health System. Web.
National Center for Biotechnology Information. PubChem Compound Database; CID=7847, https://pubchem.ncbi.nlm.nih.gov/compound/7847.
Naz, Shahina, Rahmanullah Siddiqi, Hina Sheikh, and Syed Asad Sayeed. “Deterioration of Olive, Corn and Soybean Oils Due to Air, Light, Heat and Deep-frying.” Food Research International 38.2 (2005): 127-34. Web.