According to a study published by the journal JAMA Internal Medicine, the Mediterranean diet reduces the risk of developing breast cancer by two thirds. These results are based on a large set of clinical trials coordinated by the Universidad de Navarra working as part of a larger multi-center study by the PREDIMED (Prevention with the Mediterranean Diet) group, and including the Center for Biomedical Research in the Physiopathology Network of the Obesity and Nutrition center CIBERobn.

According to lead Professor of Preventative Medicine and Public Health, Miguel Ángel Martínez-González, coordinator of the study and researcher of the Institute of Health Research in Navarra (IDISNA), it is the first scientific study that demonstrates the preventive value of the Mediterranean diet against breast cancer with randomized trials. "Studies done until now have been based on observation. This is the first study that offers highly scientific results over an average of 4.8 years in a trial of 4,282 women."

The participants, coming from all over Spain, followed three types of diets: a Mediterranean diet rich in extra virgin olive oil, a Mediterranean diet with the addition of nuts, and a diet low in fat to function as a control group. In the first two groups, the results from the participants confirm that they had one third of the incidence of the disease as compared to the control group. According to the authors of the study the high consumption of virgin olive oil in the Mediterranean diet, where olive oil comprises at least 15% of total consumed calories, explains in large part the protection against breast cancer. "Even though the control group, or the comparison group, also followed a diet that has already been considered healthy, the results could have been even more significant if they had compared those following a normal diet in western but not Mediterranean countries," clarified Dr. Martínez-González. These results agree with those obtained in many observational studies, some having taken place in Spain and also financed through the Carlos III Institute of Health. This same institute now hopes for greater scientific evidence through attempting further randomized clinical studies.

Healthy Diet Against Breast Cancer

Within all the evidence, there were only 35 diagnosed cases of the disease. "Keeping in mind that breast cancer is the disease that takes away the most years of life from women in Spain – one in 13 women will develop this tumor at some time in their life – the results of the study propose a great step forward in the field of prevention," underlined Estefanía Toledo, researcher of the School of Medicine of the University of Navarra and main author of the study.

In her opinion, the preventative strategies propose the most effective tools to fight against this invasive tumor. "In this sense, dietic intervention could have especially valuable results because it can be used in primary care centers (health centers) and, in the case of the Mediterranean diet, can contribute to other benefits that have already been shown such as the prevention of diabetes type 2, cardiovascular disease and obesity," added the researcher from IDISNA. Nevertheless, the conclusions of this work suggest the need to do further studies with a wider sample in order to further confirm the results of this study.

This research project counted on the collaboration of the National Health Service of Navarra (Osasunbidea) and the participation of Rovirai Virgili University of Tarragona, as well as other centers mentioned in PREDIMED's network of researchers.