A large randomized individual and group intervention conducted by registered dietitians increased adherence to Mediterranean-type diets:: The PREDIMED study

Objective To assess the effectiveness of an intervention aimed to increase adherence to a Mediterranean diet. Design A 12-month assessment of a randomized primary prevention trial. Subjects/settings One thousand five hundred fifty-one asymptomatic persons aged 55 to 80 years, with diabetes or >= 3 cardiovascular risk factors. Intervention Participants were randomly assigned to a control group or two Mediterranean diet groups. Those allocated to the two Mediterranean diet groups received individual motivational interviews every 3 months to negotiate nutrition goals, and group educational sessions on a quarterly basis. One Mediterranean diet group received free virgin olive oil (1 L/week), the other received free mixed nuts (30 g/day). Participants in the control group received verbal instructions and a leaflet recommending the National Cholesterol Education Program Adult Treatment Panel III dietary guidelines. Main outcome measures Changes in food and nutrient intake after 12 months. Statistical analyses Paired t tests (for within-group changes) and analysis of variance (for between-group changes) were conducted. Results Participants allocated to both Mediterranean diets increased their intake of virgin olive oil, nuts, vegetables, legumes, and fruits (P < 0.05 for all within- and between-group differences). Participants in all three groups decreased their intake of meat and pastries, cakes, and sweets (P < 0.05 for all). Fiber, monounsaturated fatty acid, and polyunsaturated fatty acid intake increased in the Mediterranean diet groups (P < 0.005 for all). Favorable, although nonsignificant, changes in intake of other nutrients occurred only in the Mediterranean diet groups. Conclusions A 12-month behavioral intervention promoting the Mediterranean diet can favorably modify an individual's overall food pattern. The individual motivational interventions together with the group sessions and the free provision of high-fat and palatable key foods customary to the Mediterranean diet were effective in improving the dietary habits of participants in this trial.