Mediterranean Diet and Mortality: A Second Meta-Analysis
Commentary by: Jacob Schor, ND, FABNO
Reference: Sofi F, Abbate R, Gensini GF, Casini A. Accruing evidence on benefits of adherence to the Mediterranean diet on health: an updated systematic review and meta-analysis. Am J Clin Nutr. 2010;92(5):1189-1196.
Study Design: The newest of the Francesco Sofi papers, this study added data from 7 prospective studies, published in the last 2 years, to an earlier meta-analysis published in 2008. The statistical analysis of the compiled data correlated adherence to a Mediterranean diet with relative risk of several diseases and overall mortality risk. These new additions included 1 study for overall mortality, 3 studies for cardiovascular incidence or mortality, 1 study for cancer incidence or mortality, and 2 studies for neurodegenerative diseases.
Participants: The number of subjects whose data was compiled varied by condition. For cardiovascular disease incidence and mortality, there were a total of 534,064 subjects with 8,739 events compiled for analysis. For cancer incidence and mortality, there were 1,006,410 subjects and 11,378 events. For neurodegenerative diseases, there were 136,235 subjects and 1,074 cases from which to draw conclusions. The earlier 2008 meta-analysis utilized data from 12 qualifying studies published between 1966 and 2008 with a total of 1,574,299 subjects.1
Study Intervention: Adherence to a Mediterranean diet was defined via scores that estimated the conformity of the subject’s dietary pattern with the traditional Mediterranean dietary pattern. Values of zero or 1 were assigned to each of 7 to 9 different dietary characteristics by using medians of consumption among the study participants as the divider. People whose consumption was characteristic of a Mediterranean diet (vegetables, fruits, beans, cereals, fish, olive oil, and a moderate intake of red wine during meals) above the median consumption were given 1 point for each characteristic in which they were above average. A zero score was given to those with consumptions below the median. People whose consumption patterns of components not considered to be part of a Mediterranean diet (red and processed meats, poultry, eggs, or dairy products) was above the median consumption also had a zero assigned, while those at or below the median received 1 point for that category. Different studies varied in the total number of food categories scored. Thus while lowest score was always zero, the highest possible scores varied among the studies from 7 to 9 points for greatest adherence.
Primary Outcome Measures: The study calculated changes in relative risk of either incidence of or mortality from cardiovascular disease, cancer, or neurodegenerative diseases associated with greater adherence to a Mediterranean diet. Relative risk of total mortality was also calculated.
Key Findings: This paper is an update of Sofi et al 2008, adding data from newly published studies. The increased quantity of data did not have a substantial effect on Sofi’s original findings. This new meta-analysis showed that a 2-point increase in adherence to the Mediterranean diet was associated with a significant reduction of overall mortality [relative risk (RR)=0.92; 95% CI: 0.90, 0.94], cardiovascular incidence or mortality (RR=0.90; 95% CI: 0.87, 0.93), cancer incidence or mortality (RR=0.94; 95% CI: 0.92, 0.96), and neurodegenerative diseases (RR=0.87; 95% CI: 0.81, 0.94)./p>
Practice Implications: The exact definition of the Mediterranean diet is frustratingly vague. It is more a concept than a defined intervention. Clearly there are elements to this diet that provide health benefit. It is also clear that exactitude is not required nor does it take large dietary changes to provide benefit. To achieve the minimal 2-point adherence score increase required to see significant benefit only required improvement in 2 out of 7 or 9 different categories. For example, to achieve a 2-point score increase in adherence, one might only need to increase fish consumption above the mean amounts in the cohort of subjects in the study and decrease red meat consumption below the cohort’s mean. Someone starting with a diet that is far from the Mediterranean pattern could easily score 0 points and with changes in their eating habits increase their score by 7 to 9 points.
References
1. Sofi F, Cesari F, Abbate R, Gensini GF, Casini A. Adherence to Mediterranean diet and health status: meta-analysis. BMJ. 2008;337:a1344.
About Jacob Schor, ND, FABNO
Jacob Schor, ND, FABNO, is a graduate of National College of Naturopathic Medicine and now practices in Denver. He served as president to the Colorado Association of Naturopathic Physicians, and is now on the board of directors of the Oncology Association of Naturopathic Physicians and is recognized as a Fellow by the American Board of Naturopathic Oncology. He serves on the editorial board for the International Journal of Naturopathic Medicine. In 2008, he was awarded the Vis Award by the American Association of Naturopathic Physicians. His writing appears often in Naturopathy Digest and Naturopathic Doctor News and Review.
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