Fried in Olive Oil: Big Spanish Study Finds No Heart Link

A large Spanish study published in the BMJ this week found no link between eating fried food and heart disease or early death among 40,757 adults whose food was fried mostly in olive or sunflower oil. It followed people for a median of eleven years. Here is what the researchers found, why the result applies to Spanish-style frying rather than to fried food in general, and what it does and does not mean for your kitchen.

What the study found

The research, led by Pilar Guallar-Castillón of the Autonomous University of Madrid, used the Spanish part of the European Prospective Investigation into Cancer and Nutrition, known as EPIC. Between 1992 and 1996 the team recruited adults aged 29 to 69 who had no heart disease, asked them in detail what they ate and how they cooked it, including which oil they fried in, and then followed them until 2004 through hospital, heart attack and death registers.

Over that time there were 606 coronary heart disease events and 1,135 deaths. When the researchers split people into four groups by how much fried food they ate, those in the top group were no more likely to have heart disease than those in the bottom group, once age, sex, energy intake and other factors were taken into account. The results were the same for people who fried in olive oil and for those who used sunflower oil, and there was no link with deaths from any cause either.

A hazard ratio of 1 means no difference, and every one of those intervals includes 1, which is why the authors conclude there was no association. In a linked editorial, Michael Leitzmann of the University of Regensburg wrote that the study challenges the idea that frying food is generally bad for the heart, while stressing that both the food being fried and the oil used matter.

Why the context matters

The authors are careful about where their result applies. As Spain’s trade press reported, they acknowledge the findings would probably not be the same in countries where people fry differently. Olive Oil Times, summarizing the paper, noted the researchers’ warning that frying in other fats, reusing oil many times or eating salty fried snacks may still be harmful. Spanish home frying typically uses liquid oil, often olive oil, and fresh ingredients, which is a long way from a fast-food fryer.

• It is an observational study: it shows no link, it does not prove fried food is good for you.
• Diet was reported by the participants, which always carries some error.
• Fried food still adds calories, and weight matters for heart health.

Our look at olive oil and heart health sets out what the wider evidence supports, and our piece on oxidative stability explains why olive oil holds up well to heat. If you want the Spanish method in practice, see frying eggs in olive oil the Spanish way.

This article is general information, not medical advice. If you have heart disease, high cholesterol or other risk factors, talk to your doctor or a registered dietitian about your diet, and see a doctor promptly about chest pain or shortness of breath.

Sources

• Guallar-Castillón P. 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:e363 (January 23, 2012)
• PubMed abstract of the BMJ study
• Óleo Revista, “La comida frita en aceite de oliva o girasol no aumenta el riesgo de enfermedad cardiovascular” (January 26, 2012)