One of the most common food myths is that while olive oil is healthy, it should not be used for cooking or frying. The belief is that somehow the high heat used in cooking or frying makes olive oil unhealthy. However, this belief is not consistent with historical uses of olive oil in Mediterranean cooking, nor with a wide body of published research. There is no scientific evidence to support the fact that Olive Oil is harmful to your health when heated.
Here are the facts:
Vegetable oils oxidize as they age and are exposed to air and light. This process is accelerated when they are heated .
Some of the oxidation products are toxic, but we have good natural defenses against such substances.
The ease of oxidation of an oil is influenced by its degree of unsaturation. Polyunsaturated oils oxidise more easily than saturated oils.
Corn oil and sunflower oil contain high proportions of polyunsaturated oils; they oxidise easily. Coconut oil is high in saturated oils; it doesn’t oxidise easily.
Olive oil contains a high proportion of monounsaturated oil. It oxidises less easily than polyunsaturated oils .
Virgin and extra-virgin olive oils also contain antioxidants which help resist oxidation as the oil is heated . Several studies have shown that virgin olive oil produces fewer oxidation products than polyunsaturated oils when heated.
If an oil is heated beyond its smoke point, it gives off toxic smoke. The smoke point of olive oil is around 200°C. Some refined oils, such as palm, peanut, safflower and soybean oils can have smoke points around 230°C to 260°C, but unrefined oils can have smoke points in the low hundreds.
There are no studies showing evidence of damage to the health of humans resulting from oxidation products of cooking oils.
In conclusion, Olive oil certainly doesn’t deserve to be singled out as a source of toxins in cooking. There are oils that are far worse, and in any case, as long as you don’t use extreme temperatures or cooking times, the amount of oxidation product will be small.