Predimed

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PREDIMED (Prevention with Mediterannean Diet) was a large Spanish study that looked at whether a Mediterranean-style diet could prevent heart problems in people at high risk. It involved 7,447 adults aged 55–80 who did not have cardiovascular disease at the start. Participants were randomly assigned to three diet groups with intensive coaching: two Mediterranean diet variants (one focusing on extra-virgin olive oil, the other on nuts) and a low-fat control diet. The study planned to go for six years but ended early after about 4.8 years.

The main finding was that both Mediterranean groups reduced the risk of a major heart event (heart attack, stroke, or death from heart disease) by about 30%. This equated to roughly 3 fewer such events per 1,000 people per year of follow-up. Additional benefits included fewer cases of peripheral artery disease, fewer breast cancer cases, and fewer atrial fibrillation cases in the olive oil group.

Critics noted several issues: the low-fat control group’s plan changed during the trial, there were more dropouts in the control group, and the control diet might not have truly been very low in fat. The participants lived in a Mediterranean country, so it’s unclear if the results apply the same way in non-M Med settings. Despite these concerns, the Mediterranean diet is still seen as the strongest dietary pattern for cardiovascular benefit in this and related studies.

Publication history: the main paper reporting the results was retracted and later republished in 2018 after corrections to statistical methods. The trial involved eleven field centers, began in 2003 in Navarre, and completed around 2011, with the final cardiovascular results published in 2013 and then updated in 2018. Lead coordinators were Estruch and Martinez-González.