There has been a lot of news recently about a NEJM randomized trial Spanish study of diets that shows statistically significant benefits of two Mediterranean diets, one providing free olive oil, the other providing free nuts (mostly walnuts), along with other diet recommendations.Scientists randomly assigned 7,447 men and women in Spain over age 55 who were overweight, were smokers, or had diabetes or other risk factors for heart disease to follow the Mediterranean diet or a low-fat diet as the control group. Here is the key paragraph from the NY Times.
"One group assigned to a Mediterranean diet was given extra-virgin olive oil each week and was instructed to use at least 4 four tablespoons a day. The other group got a combination of walnuts, almonds and hazelnuts and was instructed to eat about an ounce of the mix each day. An ounce of walnuts, for example, is about a quarter cup — a generous handful."
The articles in the Times and Post have emphasized that it was the Mediterranean diet, but the following important blog from Dr. Aaron Carroll, highlights that it very likely that the effects were solely due to increased olive oil and nuts, since the three groups do not differ meaningfully in their consumption of other foods (red meat, fish, vegetables, fruit, grains, red wine, etc.). Hence instead of saying "Go Mediterranean", it should have said "Eat Olive Oil and Nuts" to reduce heart and stroke risks.
See table linked in this blog.
Now we’re all going Mediterranean?
More work should be done in this area.
Here is the full cite and abstract from the NEJM.
Primary Prevention of Cardiovascular Disease with a Mediterranean Diet
Ramón Estruch, M.D., Ph.D., Emilio Ros, M.D., Ph.D., Jordi Salas-Salvadó, M.D., Ph.D., Maria-Isabel Covas, D.Pharm., Ph.D., Dolores Corella, D.Pharm., Ph.D., Fernando Arós, M.D., Ph.D., Enrique Gómez-Gracia, M.D., Ph.D., Valentina Ruiz-Gutiérrez, Ph.D., Miquel Fiol, M.D., Ph.D., José Lapetra, M.D., Ph.D., Rosa Maria Lamuela-Raventos, D.Pharm., Ph.D., Lluís Serra-Majem, M.D., Ph.D., Xavier Pintó, M.D., Ph.D., Josep Basora, M.D., Ph.D., Miguel Angel Muñoz, M.D., Ph.D., José V. Sorlí, M.D., Ph.D., José Alfredo Martínez, D.Pharm, M.D., Ph.D., and Miguel Angel Martínez-González, M.D., Ph.D. for the PREDIMED Study Investigators
February 25, 2013DOI: 10.1056/NEJMoa1200303
Abstract: The traditional Mediterranean diet is characterized by a high intake of olive oil, fruit, nuts, vegetables, and cereals; a moderate intake of fish and poultry; a low intake of dairy products, red meat, processed meats, and sweets; and wine in moderation, consumed with meals. In observational cohort studies and a secondary prevention trial (the Lyon Diet Heart Study), increasing adherence to the Mediterranean diet has been consistently beneficial with respect to cardiovascular risk. A systematic review ranked the Mediterranean diet as the most likely dietary model to provide protection against coronary heart disease. Small clinical trials have uncovered plausible biologic mechanisms to explain the salutary effects of this food pattern. We designed a randomized trial to test the efficacy of two Mediterranean diets (one supplemented with extra-virgin olive oil and another with nuts), as compared with a control diet (advice on a low-fat diet), on primary cardiovascular prevention.