Primary Prevention of Cardiovascular Disease with a Mediterranean DietRamón Estruch, M.D., Ph.D., Emilio Ros, M.D., Ph.D., Jordi Salas-Salvadó, M.D., Ph.D., Maria-Isabel Covas, D.Pharm., Ph.D., Dolores Corella, D.Pharm., Ph.D., Fernando Arós, M.D., Ph.D., Enrique Gómez-Gracia, M.D., Ph.D., Valentina Ruiz-Gutiérrez, Ph.D., Miquel Fiol, M.D., Ph.D., José Lapetra, M.D., Ph.D., Rosa Maria Lamuela-Raventos, D.Pharm., Ph.D., Lluís Serra-Majem, M.D., Ph.D., Xavier Pintó, M.D., Ph.D., Josep Basora, M.D., Ph.D., Miguel Angel Muñoz, M.D., Ph.D., José V. Sorlí, M.D., Ph.D., José Alfredo Martínez, D.Pharm, M.D., Ph.D., and Miguel Angel Martínez-González, M.D., Ph.D. for the PREDIMED Study Investigators
February 25, 2013
Pour on the olive oil, preferably over fish and vegetables.
One of the longest and most scientific tests of a Mediterranean diet suggests this style of eating can cut the chance of suffering heart-related problems, especially strokes, in older people at high risk of them.
The study involved about 7,500 people in Spain. Half had diabetes and most had high blood pressure and cholesterol. They were told to follow a low-fat diet or a Mediterranean one with extra olive oil or nuts. That meant lots of fruit, fish, chicken, beans, tomato sauce, salads and wine.
After nearly five years, those who ate Mediterranean-style had a 30 percent lower risk of major cardiovascular problems compared to the low-fat group.
The traditional Mediterranean diet is characterized by a high intake of olive oil, fruit, nuts, vegetables, and cereals; a moderate intake of fish and poultry; a low intake of dairy products, red meat, processed meats, and sweets; and wine in moderation, consumed with meals. In observational cohort studies, and a secondary prevention trial (the Lyon Diet Heart Study), increasing adherence to the Mediterranean diet has been consistently beneficial with respect to cardiovascular risk.
Participant Selection and Randomization
Eligible participants were men (55 to 80 years of age) and women (60 to 80 years of age) with no cardiovascular disease at enrollment, who had either type 2 diabetes mellitus or at least three of the following major risk factors: smoking, hypertension, elevated low-density lipoprotein cholesterol levels, low high-density lipoprotein cholesterol levels, overweight or obesity, or a family history of premature coronary heart disease.
Beginning on October 1, 2003, participants were randomly assigned, in a 1:1:1 ratio, to one of three dietary intervention groups:
1. a Mediterranean diet supplemented with extra-virgin olive oil,
2. a Mediterranean diet supplemented with nuts,
3. or a control diet.
Baseline Characteristics of the Study Participants
Participants were followed for a median of 4.8 years (interquartile range, 2.8 to 5.8). After the initial assessment, 209 participants (2.8%) chose not to attend subsequent visits, and their follow-up was based on reviews of medical records.
As with many clinical trials, the observed rates of cardiovascular events were lower than anticipated, with reduced statistical power to separately assess components of the primary end point. However, favorable trends were seen for both stroke and myocardial infarction. We acknowledge that, even though participants in the control group received advice to reduce fat intake, changes in total fat were small and the largest differences at the end of the trial were in the distribution of fat subtypes.
The interventions were intended to improve the overall dietary pattern, but the major between-group differences involved the supplemental items. Thus, extra-virgin olive oil and nuts were probably responsible for most of the observed benefits of the Mediterranean diets. Differences were also observed for fish and legumes but not for other food groups.