Home > DARE Reviews > Meta-analysis comparing Mediterranean to...

PubMed Health. A service of the National Library of Medicine, National Institutes of Health.

Database of Abstracts of Reviews of Effects (DARE): Quality-assessed Reviews [Internet]. York (UK): Centre for Reviews and Dissemination (UK); 1995-.

Database of Abstracts of Reviews of Effects (DARE): Quality-assessed Reviews [Internet].

Meta-analysis comparing Mediterranean to low-fat diets for modification of cardiovascular risk factors

AJ Nordmann, K Suter-Zimmermann, HC Bucher, I Shai, KR Tuttle, R Estruch, and M Briel.

Review published: 2011.

Link to full article: [Journal publisher]

CRD summary

This review concluded that Mediterranean diets appeared to be more effective than low-fat diets in inducing clinically relevant long-term changes in cardiovascular risk factors. Although the conclusions reflected the evidence presented, they should be interpreted with caution given the limited quality of included trials and high level of variation observed in pooled clinical outcome findings.

Authors' objectives

To compare the effects of Mediterranean diets versus low-fat diets on cardiovascular risk factors.

Searching

The following databases were searched from inception to January 2011 with no language restrictions: MEDLINE, EMBASE, BIOSIS, Web of Science and Cochrane Central Register of Controlled Trials (CENTRAL). Search terms were reported. Reference lists of retrieved publications and relevant reviews were screened. Clinical trial registries were searched for ongoing trials. Experts in the field were contacted for relevant studies.

Study selection

Randomised controlled trials (RCTs) that compared Mediterranean diets with low-fat diets (aiming at an energy intake with ≤30% of calories from fat) in overweight/obese patients with at least one additional cardiovascular risk factor (primary prevention) or patients with established coronary artery disease (secondary prevention) were eligible for inclusion. Trials were included if they define Mediterranean as those with moderate fat intake, rich in vegetables and low in red meat. Eligible trials had to have a minimum follow-up of six months and report intention-to-treat data on changes of body weight, blood pressure and lipid values.

Most included trials were primary prevention trials; one was a secondary prevention trial. Half of the included trials had unbalanced co-interventions between Mediterranean diet and low-fact diet groups, with only the Mediterranean diet group receiving specific individualised programmes. The mean age of included patients ranged from 35 to 68 years. Mean body mass index at baseline ranged from 29kg/m2 to 35kg/m2. Over half of the included studies did not restrict calorie intake in either group. Most trials were conducted in Mediterranean countries.

Two reviewers independently assessed studies for inclusion.

Assessment of study quality

The quality of trials was assessed using criteria for allocation concealment, blinding, loss to follow-up and withdrawals, proportion of patients with complete follow-up, and trials not stopped early for benefit.

Two reviewers independently performed quality assessment.

Data extraction

Data were extracted on means and standard deviations at baseline and two-year follow-up to calculate mean differences with 95% confidence intervals. Where standard deviations were not reported, the estimates for standard deviations were calculated from P values. Trial authors were contacted for any additional data where necessary.

Two reviewers independently performed data extraction.

Methods of synthesis

The trials were combined in a meta-analysis. Weighted mean differences with 95% confidence intervals were calculated using a random-effects model. Statistical heterogeneity was assessed using the Cochran Q test and Ι².

Sensitivity analyses were performed on a basis of a number of variables, including trial quality, primary versus secondary prevention trials, and balanced versus unbalanced co-interventions.

Publication bias was assessed using funnel plots.

Results of the review

Seven RCTs were included in the review (3,650 patients). All trials had an open design. Allocation concealment was adequate in five trials. Blinding assessment for all outcomes was adequate in two trials. Follow-up ranged from two to four years (where reported). Most trials had rates of loss to follow up less than 10%. No trial was stopped early for benefit.

Compared with low-fat diets, Mediterranean diets were associated with a significant reduction in body weight (WMD -2.24kg, 95% CI -3.85 to -0.63; six RCTs), body mass index (WMD -0.56 kg/m2, 95% CI -1.01 to -0.11; six RCTs), systolic blood pressure (WMD -1.70mmHg, 95% CI -3.35 to -0.05; six RCTs), diastolic blood pressure (WMD -1.47mmHg, 95% CI -2.14 to -0.81; six RCTs), and total cholesterol (WMD -7.35mg/dL, 95% CI-10.32 to -4.39; six RCTs) at two years follow-up. Substantial heterogeneity was observed for these outcomes (Ι² ranged from 60% to 97%).

Sensitivity analyses did not materially alter the results. There was no evidence of publication bias.

Authors' conclusions

Mediterranean diets appeared to be more effective than low-fat diets in inducing clinically relevant long-term changes in cardiovascular risk factors.

CRD commentary

The review inclusion criteria were clear. A number of relevant databases were searched. Efforts were made to find published and unpublished studies with no language restrictions, which minimised the potential for publication and language biases. Sufficient attempts were made to minimise errors and biases in the review process.

Appropriate criteria were used to assess trial quality. Statistical heterogeneity was assessed and sources of heterogeneity were explored. Appropriate methods were used to pool the results. Most of the trials were conducted in Mediterranean countries, which limited the generalisability of results to other regions.

Although the authors' conclusions reflected the evidence presented, they should be interpreted with caution given the limited quality of included trials and high level of heterogeneity observed for the pooled outcomes.

Implications of the review for practice and research

Practice: The authors did not state any implication for practice.

Research: The authors stated that, before the implementation of Mediterranean diet in individuals with an increased vascular risk, further research (particularly for adequately powered cardiovascular disease prevention trial) was required to reproduce the observed beneficial results of Mediterranean diets on cardiovascular risk factors and cardiovascular morbidity and mortality.

Funding

Forlen Foundation.

Bibliographic details

Nordmann AJ, Suter-Zimmermann K, Bucher HC, Shai I, Tuttle KR, Estruch R, Briel M. Meta-analysis comparing Mediterranean to low-fat diets for modification of cardiovascular risk factors. American Journal of Medicine 2011; 124(9): 841-851. [PubMed: 21854893]

Indexing Status

Subject indexing assigned by NLM

MeSH

Adult; Aged; Body Mass Index; Cardiovascular Diseases /diet therapy /prevention & control; Diet, Fat-Restricted; Diet, Mediterranean; Diet, Reducing; Exercise; Female; Humans; Male; Middle Aged; Myocardial Infarction /diet therapy /prevention & control; Obesity /diet therapy; Overweight /diet therapy; Randomized Controlled Trials as Topic; Risk Factors; Sedentary Lifestyle; Waist Circumference

AccessionNumber

12011005545

Database entry date

10/04/2013

Record Status

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.

CRD has determined that this article meets the DARE scientific quality criteria for a systematic review.

Copyright © 2014 University of York.

PMID: 21854893

Download

PubMed Health Blog...

read all...

Recent Activity

Your browsing activity is empty.

Activity recording is turned off.

Turn recording back on

See more...