Contrary to conventional wisdom, people are hearing more and more that olive oil – the “healthy oil” – is not safe to cook with at high heat. This is true.  Though olive oil is generally considered healthy, its medicinal properties are lost when it is cooked at high temperatures.  This is a frustrating development for those who happily use olive oil, rather than other types of oils, when sautéing their onions and garlic.

You need to understand two concepts when choosing oils to cook with: smoke point and refined vs. unrefined oils.

Smoke point is the temperature oil can be heated before it smokes, discolors and starts to decompose. If this temperature is reached, the biochemical structure of oil is changed and free radicals are produced. This diminishes the flavor and nutritional value of the oil and it is no longer safe to consume. Free radicals accelerate the aging process and contribute to developing heart disease and cancer.

Unrefined cooking oils have not been processed. They are highest in nutrients, fullest in flavor and have the lowest smoke point. Unrefined oils should not be over-heated. Refined cooking oils have been processed to remove impurities and have higher smoke points then their unrefined counterparts. The refining process raises the oil’s smoke point so that it will be safer to use while cooking. Consumers need to be aware that many common cooking oils come in both refined and unrefined forms. For example, unrefined cold-pressed extra virgin olive oil has the lowest smoke point at around 200°F whereas “pure olive oil” (also referred to as “light”) which has been refined, has its smoke point around 400°F.

A few more clarifications…

Extra-virgin olive oil is derived from the very first mechanical pressing of the olives.

Fine Virgin olive oil is the product from the second pressing of the olives.

Refined olive oil, however, results from a process of chemically extracting oil from olives. Finally there is “pure olive oil” which is a blend of refined and virgin olive oil. The more processed and refined the olive oil, the less healthy it is for you. Refined and pure olive oils have been chemically treated and contain less nutrients than the virgin olive oils. That being said, the unhealthier refined olive oils are safer to cook with at higher temperatures.

But why use a poor quality olive oil, devoid of its much touted medicinal benefits, just to cook with at high temperatures; especially when there are much healthier and safer oils to put over a flame? My recommendation for the healthiest olive oil is organic, unrefined, cold-pressed extra virgin olive oil. Cold-pressed refers to the lack of heat to mechanically extract the oil. This has the lowest smoke point and is the most nutrient dense of all the olive oils. I would not heat this oil above 200°F. That means no stir-frying and no roasting vegetables. Instead, add olive oil to your dishes after they have been cooked. Consider, for example, steaming vegetables, taking them off the heat, and then drizzling them with olive oil, salt and pepper.

I will write more about safe cooking oils in upcoming posts.