Exploring the benefits of the Mediterranean diet: evidence from the PREDIMED trial

The Mediterranean diet, rich in vegetables, olive oil, whole grains, fruit and nuts, has been linked to numerous health benefits. Many observational studies have shown that those eating a Mediterranean diet live longer on average, and have reduced risk of heart disease, cancer and hypertension. Now, new evidence published in BMC Medicine from the Prevención con Dieta Mediterránea (PREDIMED) collaboration provides further insights into the benefits of the Mediterranean diet.

The PREDIMED study, led by a group of Spanish researchers including Miguel Ángel Martínez-González iStock photofrom the University of Navarra, Ramón Estruch from Clinic Hospital Barcelona and Jordi Salas-Salvado from Reus University, is a large clinical trial that was designed to investigate the efficacy of the Mediterranean diet for the primary prevention of cardiovascular diseases (CVD). Participants at high risk of heart disease were randomly assigned to follow a Mediterranean diet supplemented with either olive oil or nuts, and those in the control group were asked to follow a low-fat diet. Earlier this year, results from this study provided the first evidence from a clinical trial to show that eating a Mediterranean diet supplemented with olive oil or nuts reduces the risk of heart disease and stroke by 30%.

Further analysis of the trial published in BMC Medicine by Jordi Salas-Salvadó and colleagues showed that those eating nuts more than three times a week have reduced risk of mortality compared with non-consumers. In a commentary article, Sabine Rohrmann and David Faeh discuss these results, highlighting that further research should assess whether particular types of nuts should be favored, and the optimal quantity of nuts that should be consumed. Martínez-González and colleagues explored the cardioprotective effects of nuts and olive oil further in a study investigating their effects on hypertension. The authors found that although both the Mediterranean and low-fat diets have beneficial effects on blood pressure, diastolic blood pressure was reduced to a greater extent in the groups promoting increased consumption of olive oil or nuts. These results suggest that the beneficial effect on blood pressure could explain the link between Mediterranean diet and reduced CVD risk.

In addition to its cardioprotective effects, the Mediterranean diet has been linked to improvements in mental health. In a research article, Almudena Sánchez-Villegas and colleagues showed that those who eat more nuts have reduced risk of depression, and the inverse association is stronger in patients with type 2 diabetes, suggesting that a Mediterranean diet supplemented with nuts could have a positive impact on mental health. A typical Mediterranean diet also contains wine in moderate amounts, and Martínez-González and colleagues explored the effects of wine consumption on depression risk in further research analysing data from the PREDIMED study. The authors found that those drinking two to seven glasses of wine a week are less prone to depression than non-drinkers, whereas heavy drinkers are at greater risk of depression. These results reveal that the relationship between alcohol and mental health is more complex than previously thought, and the authors conclude that moderate wine consumption could reduce depression in a Mediterranean population.

Taken together, the results published in BMC Medicine from the PREDIMED study provide important evidence for the beneficial effects of the Mediterranean diet on physical and mental health. Martínez-González explained that:

“PREDIMED is the largest randomized trial with a dietary pattern ever conducted in Europe… We are finding more and more answers that can help to substantially reduce the major global causes of death and disability in the next decades if the population-wide strategy of preventive medicine is eventually adopted to improve the dietary habits of the general public.”

We look forward to future studies investigating whether the results of the PREDIMED trial can be extrapolated to other populations, and hope the results of this important study are applied in the future to improve cardiovascular and mental health.

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