Eating foods fried in olive or sunflower oil will does not increase the risk of heart disease or premature death, according to a study of 40,757 adults over an eleven-year period.

Frying is one of the most popular methods of cooking in the Western world, and because fried foods contain more calories, more fat and less water, eating large amounts of fried food is generally thought to increase some risk factors for heart disease like high blood pressure, high cholesterol and obesity.

Scientists from Madrid University, Spain, examined the health of participants between the ages of 29 to 69 who did not have heart disease in the beginning of the study by dividing them into four groups based on the level of their fried food consumption.  Individuals in the first quartile consumed the lowest amount of fried food and those in the fourth quartile consumed the highest amount.

Lead author Professor Pilar Guallar-Castillón from Autonomous University of Madrid found that over the median follow-up of 11 years, there were 606 cases of coronary heart disease and 1,135 deaths from a variety of causes.

Researchers analyzed the data by adjusting for energy intake, body mass index, high blood pressure and other risk factors and found that the risk of coronary heart disease was not significantly higher in the second, third or fourth quartiles when compared to the first.

Researchers also found that there was no difference in participants who used olive oil and those who used sunflower oil to fry their food, and that there was no association between fried food consumption and death.

The authors noted that the study was done in Spain, like other Mediterranean counties that generally use olive or sunflower oil for frying, so they said that these findings would most likely be different in countries where people fry with solid and re-used oils.  Researchers said that frying degrades oils, particularly when re-used and creates more unhealthy trans fats while losing healthier unsaturated fats, and these unhealthier fats end up in food that is consumed.

In a Mediterranean country where olive and sunflower oils are the most commonly used fats for frying, and where large amounts of fried foods are consumed both at and away from home, no association was observed between fried food consumption and the risk of coronary heart disease or death, researchers said in a statement.

Participant data was taken from a larger European Prospective Investigation into Cancer and Nutrition study, which looked into diets, health and lifestyles of about half a million participants in ten European countries. 

The study dispels the myth that frying food is generally bad for the heart, however this does not mean that frequent meals of fish and chips will have no health consequences and the type of oil used in frying food are particularly relevant to health, Professor Michael Leitzmann from the University of Regensburg in Germany said in the study's accompanying editorial.

The study was published online in the British Medical Journal on Tuesday.