The latest publication from the PREDIMED trial group reported a significant reduction in major cardiovascular events, but not overall mortality, after 5 years on a Mediterranean diet. Over 7000 persons at high cardiovascular risk were enrolled and assigned to either a low fat control group or a Mediterranean diet enriched in nuts or olive oil. Energy restriction was not specifically recommended. Both of these Mediterranean-based diets were successful, and the trial was halted just over one year early because of the significance of the results. The nut-supplemented group showed a shift in their lipid patterns to less atherogenic lipid profiles and reductions in small dense low density lipoprotein (LDL).
In a sub-study from PREDIMED reporting on patients with type 2 diabetes, Mediterranean diets supplemented with virgin olive oil or nuts reduced total body weight and improved glucose metabolism to the same extent as the usually recommended low-fat diet.The diet was effective in almost all subgroups within the trial, with the notable exception of patients with normal blood pressure. Patients with diabetes saw a benefit similar to the overall group. In contrast, lifestyle modification has been shown to prevent diabetes mellitus more consistently, but diet has been less consistent in preventing or reducing cardiovascular disease. The recent LOOK AHEAD study revealed no significant benefit of lifestyle modification on cardiovascular risk, although this paper studied only persons with pre-existing diabetes. Neither low carbohydrate diets nor addition of omega-3 fatty acids can prevent diabetes mellitus, and these diet modifications may even be associated with a higher risk of diabetes mellitus.