PREDIMED (Prevención con Dieta Mediterránea (Prevention with Mediterranean Diet[1])) was a large Spanish primary prevention trial which included 7,447 Spanish participants (55–80 years, 58% women) who were at high risk for cardiovascular disease, but otherwise healthy (initially free of cardiovascular disease).
They were randomly assigned to receive interventions with intensive education to one of three diets: The trial was planned for six years, but it was terminated early after a median follow-up of 4.8 years, and demonstrated that both Mediterranean diet groups reached a statistically significant reduction in the rate of the composite cardiovascular primary end-point of myocardial infarction, stroke, or cardiovascular death.
Other important observed benefits included a strong reduction in peripheral artery disease,[3] breast cancer,[4] and atrial fibrillation (only associated with the consumption of extra-virgin olive oil).
[6][7] Arnav Agarwal and John Ioannidis note that "republication may not solve multiple problems that remain, including the inappropriateness of stopping early given the revised results and the effects on over 200 secondary publications" and "multiple contradictions between data reported across PREDIMED publications suggest a more generic problem with the trial's quality".
[8] The trial was multicenter with eleven field centers: The field work started in 2003 in the vanguard center of PREDIMED-NAVARRA (University of Navarra)[9] and the trial was completed in 2011 following the recommendation of the Data and Safety Monitoring Board, Xavier Pi-Sunyer, Frank B. Hu, Joan Sabaté and Carlos A. González).