The cardiovascular benefits of the Mediterranean Diet (or MD) have been in the news lately. The newspaper stories were based on an article published in The New England Journal of Medicine (issue of February 25, 2013, by R. Estruch et.al.). But since even the New York Times did not give a fully accurate description of the MD or the study and its results, I thought I would do so here.
To quote from the article: "The MD 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 meats, processed meats; and sweets and wine consumed in moderation with meals". Over 7,000 male and female adults in Spain were admitted to the study, and all were given periodic instruction and review by nutritionists about the MD. The adults, who ranged in age from 55 to 80, were split into three groups: one group was given extra olive oil (1 liter per week), one group was given extra nuts (30 grams of mixed walnuts, hazelnuts and almonds per week), and the third group was given periodic reinforcements about the design and benefits of a low fat diet.
There were no restrictions placed on the total caloric intake, and no advice about increasing physical activity. In addition, although none of the study patients had any evidence of cardiovascular disease, all were at risk for developing this problem: they either had adult-onset diabetes, or they had three or more of the following risk factors: smoking, hypertension,elevated LDL cholesterol, low HDL cholesterol, overweight or obesity, or a family history of premature heart disease. The primary endpoint was heart attack, stroke or death from cardiovascular disease.
The two MD groups increased their fish consumption by 0.3 servings/week, increased their legume consumption by 0.4 servings per week, and they increased their consumption of olive oil to 50 or 32 grams per day. No change in physical activity was observed. In the 5 year follow, there were 288 events noted: 96 with extra olive oil, 83 with extra nuts, and 109 in the control group who were encouraged about a low fat diet. Only the reduction in stroke risk reached statistical significance, and the calculated benefit was 3 major cardiovascular events per 1000 person-years.
I think it would be fair to say that any intervention in a group at elevated risk for cardiovascular disease would be beneficial, but it is scientifically difficult to extrapolate the above results to normal, healthy individuals with no health risks, especially if they live in a country with a low mortality rate, such as Japan.
Added note: The hard copy was just published in The New England Journal of Medicine, vol. 368, pp 1279-1290, April 4, 2013, by R. Estruch et. al.