The BMJ study revealed that the consumption of fried foods in Spain – a country where olive or sunflower oil is used for frying – was not associated with incidence of coronary heart disease or with all cause mortality.
However the research team, led by Professor Pilar Guallar-Castillón from Autonomous University of Madrid, warned that their findings only apply to frying in olive oil and sunflower oil – adding that their results would probably not be the same in other countries where solid and re-used oils were used for frying.
“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,” said Guallar-Castillón and his team.
Frying - the risk?
In many Western countries, frying is one of the most common methods of cooking foods.
The authors noted that the consumption of fried food has been associated with some cardiovascular risk factors, including high blood pressure (hypertension), obesity, and low levels of high density lipoprotein (HDL) cholesterol. While consumption of fried food can increase some of these heart disease risk factors, a definitive association between fried food and heart disease has not been fully investigated, said Guallar-Castillón and his team.
Writing in an accompanying BMJ editorial (doi:10.1136/bmj.d8274), Professor Michael Leitzmann from the University of Regensburg, Germany, said the study results expose the myth that “frying food is generally bad for the heart.” However he stressed that the results do not mean “frequent meals of fish and chips will have no health consequences.”
"The study suggests that specific aspects of frying food are relevant, such as the oil used, together with other aspects of the diet," he added.
The British Heart Foundation echoed the view of Leitzmann, noting that the study also used a typical Mediterranean diet, rather than a Northern European diet, and as such may not be true of such a diet.
The team surveyed the cooking methods of 40,757 adults over an 11-year period, using data from the Spanish arm of the EPIC study. None of the participants had heart disease when the study began, explained the authors.
Trained interviewers asked all the participants about diet and cooking methods. The participants’ diet was then divided into ranges of fried food consumption, the first quartile related to the lowest amount of fried food consumed and the fourth indicated the highest amount.
For definite coronary heart disease events, no association with fried food consumption, revealed the authors, adding that their results did not vary between those who used olive oil for frying and those who used sunflower oil.
“Likewise, no association was observed between fried food consumption and all cause mortality,” confirmed Guallar-Castillón and his team.
Commenting on the study Leitzmann said the findings “suggests that specific aspects of frying food are relevant, such as the oil used, together with other aspects of the diet.”
He argued that future research should focus on characterising fried foods in more detail, “by including information on the type of oil used for frying, the type of frying procedure performed (deep fried or pan fried), the time and temperature used for frying, and the degree to which oils are reused.”
“Such improvements in dietary assessment should help disentangle the myths from the facts when evaluating the potential effects of fried foods on human nutrition and health,” said Leitzmann.
Published online ahead of print, Volume 344, doi: 10.1136/bmj.e363
“Consumption of fried foods and risk of coronary heart disease: Spanish cohort of the European Prospective Investigation into Cancer and Nutrition study”
Authors: P. Guallar-Castillón,F. Rodríguez-Artalejo,E. Lopez-Garcia, L.M. León-Muñoz, P. Amiano, et al