Heart disease is the main cause of death in developed countries. However, people in some developed countries in the Mediterranean region die of heart disease less often than people in other countries. This observation has led some scientists to suggest that the Mediterranean diet may decrease death from heart disease. The Mediterranean diet is characterized by large amounts of olive oil, nuts, whole grains, fruits, and vegetables. The Mediterranean diet is made up of foods with larger amounts of “healthy” oil and fat, which contradicts traditional recommendations to prevent heart disease by decreasing oil and fat intake. The effects of a higher-fat diet on risk for heart disease compared with those of a lower-fat diet are not clear. Which, if any, components of the diet have a protective effect is also unclear.