The PREDIMED study is a large, randomized controlled trial that was conducted in Spain to investigate the health benefits of the Mediterranean diet. The study was designed to determine whether a Mediterranean diet supplemented with extra-virgin olive oil or nuts could reduce the risk of cardiovascular disease in high-risk individuals.

The study included over 7,400 participants who were between the ages of 55 and 80 years and had either type 2 diabetes or at least three cardiovascular risk factors, such as smoking, hypertension, or high cholesterol. The participants were randomly assigned to one of three groups: a Mediterranean diet supplemented with extra-virgin olive oil, a Mediterranean diet supplemented with mixed nuts, or a control group that was advised to follow a low-fat diet.

The Mediterranean diet used in the PREDIMED study was based on traditional Mediterranean cuisine, and included foods such as fruits, vegetables, whole grains, fish, nuts, and olive oil. The participants in the two Mediterranean diet groups were also encouraged to consume moderate amounts of wine with meals.

The study found that both Mediterranean diet groups had a significantly lower risk of cardiovascular disease compared to the control group. Specifically, the risk of cardiovascular disease was reduced by 30% in the group consuming the Mediterranean diet with extra-virgin olive oil, and by 28% in the group consuming the Mediterranean diet with mixed nuts.

The study also found that the Mediterranean diet was associated with a lower risk of stroke, and that it had a positive impact on blood pressure, cholesterol levels, and blood sugar control.

The PREDIMED study is considered to be one of the most important studies in the field of nutrition research, and has contributed significantly to our understanding of the health benefits of the Mediterranean diet.