It is generally recommended that fried food is avoided or consumed sparingly. However, vegetable-based dishes fried in olive oil were common in traditional Mediterranean diets without, it appears, the negative health effects we associate with fried foods.The reason for this may be that the foods are fried in olive oil, and not in unhealthy seed oils.

A British study had already shown that occasional consumption of fried foods was not associated with coronary heart disease events, as long as the food was fried in fresh (not re-used) olive oil and the individuals were following a Mediterranean diet.

Now, a new study published in the Journal of Agriculture and Food Chemistry, analyzed the repeated deep frying and pan frying in 4 different refined oils: olive, corn, soybean, and sunflower. The researchers evaluated the status of the oils after being heated ten times, measuring several chemical parameters.

The refined olive oil had the highest resistance and lowest deterioration of quality compared to all of the others. The highest deterioration occurred in the refined sunflower oil.

The findings are even more significant in the context of commercial frying, such as in restaurants.

Refined olive oil is the common olive oil grade olive obtained through an industrial process of chemical refining to remove undesirable qualities such as excessive acidity and unpleasant flavors. This olive oil does not contain many of the widely touted health benefits of extra virgin olive oil, which contains a host of nutrients and antioxidants. Nevertheless it can be a useful and a healthier alternative for repeated frying compared to other cooking oils such as corn or soybean.

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• Journal of Agriculture and Food Chemistry: Monitoring of Quality and Stability Characteristics and Fatty Acid Compositions of Refined Olive and Seed Oils during Repeated Pan- and Deep-Frying Using GC, FT-NIRS, and Chemometrics
• British Medical Journal: Consumption of fried foods and risk of coronary heart disease: Spanish cohort of the European Prospective Investigation into Cancer and Nutrition study