Eating food fried in olive or sunflower oil is not associated with an increased risk of coronary heart disease or death, according to a study of more than 40,000 adults aged 29-69 years in Spain.

The benefits of olive or sunflower oil can be attributed to the fact that they are less prone to deteriorating during frying, compared to other oils.
The oil used for frying deteriorates, especially when reused, through oxidation and hydrogenation, leading to a loss of unsaturated fats and an increase in trans fats. When food is fried it loses water and absorbs this degredated oil, increasing its energy density.

The study researchers pointed out that these results are directly applicable only to other Mediterranean countries with frying methods similar to those in Spain. For example, oil (mainly olive and sunflower) rather than solid fat is used for frying in Spain. And these oils are not likely to be reused multiple times for foods eaten at home. Finally, consumption of fried snacks high in salt is fairly low in Spain, whereas in other countries such as the United States they provide an important percentage of energy intake.

“Frying with other types of fats, reusing oils several times, or consuming fried snacks high in salt may still be harmful,” the study concluded.

1. Guallar-Castillón P, Rodríguez-Artalejo F, Lopez-Garcia E, et al. Consumption of fried foods and risk of coronary heart disease: Spanish cohort of the European Prospective Investigation into Cancer and Nutrition study. BMJ 2012; 344: published 24 Jan 2012. (open access)