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Meta-Analysis Comparing Mediterranean to Low-Fat Diets for Modification of Cardiovascular Risk Factors
Study Questions:
What is the relative value of a Mediterranean diet compared to low-fat diets for modifying cardiovascular risk factors?
Methods:
MEDLINE, EMBASE, Biosis, Web of Science, and the Cochrane Central Register of Controlled Trials were searched from their inception until January 2011. Additionally, experts in the field were asked to identify randomized controlled trials (RCTs) comparing Mediterranean to low-fat diets in overweight/obese individuals, with a minimum follow-up of 6 months, reporting intention-to-treat data on cardiovascular risk factors. Two authors independently assessed trial eligibility and quality.
Results:
Six RCTs were identified that included 2,650 individuals (50% women). Mean age of enrolled patients ranged from 35 to 68 years, and mean body mass index from 29 to 35 kg/m2. After 2 years of follow-up, individuals assigned to a Mediterranean diet had more favorable changes in weighted mean differences of body weight (-2.2 kg; 95% confidence interval [CI], -3.9 to -0.6), body mass index (-0.6 kg/m2; 95% CI, -1 to -0.1), systolic blood pressure (-1.7 mm Hg; 95% CI, -3.3 to -0.05), diastolic blood pressure (-1.5 mm Hg; 95% CI, -2.1 to -0.8), fasting plasma glucose (-3.8 mg/dl; 95% CI, -7 to -0.6), total cholesterol (-7.4 mg/dl; 95% CI, -10.3 to -4.4), and high-sensitivity C-reactive protein (-1.0 mg/L; 95% CI, -1.5 to -0.5). The observed heterogeneity across individual trials could, by and large, be eliminated by restricting analyses to trials with balanced co-interventions or trials with restriction of daily calorie intake in both diet groups.
Conclusions:
The authors concluded that Mediterranean diets appear to be more effective than low-fat diets in inducing clinically relevant long-term changes in cardiovascular risk factors and inflammatory markers.
Perspective:
The observed differences for the individual risk factors were modest, but would be meaningful in large cohorts. The Lyon Diet-Heart Study, which was not included, found a 70% reduction in overall mortality with the Mediterranean diet when compared to standard post-event diet recommendations in survivors of a myocardial infarction. The Mediterranean diet was posited to be of value when the risk of cardiovascular events was found to be low in men from the island of Crete. The contents of value include high fiber, fruits and vegetables, fish, and wine.
Keywords: Cholesterol, C-Reactive Protein, Body Mass Index, Biomarkers, Dietary Fats, Overweight, Cardiovascular Diseases, Blood Pressure, Glucose, MEDLINE
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