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Effects on Health Outcomes of a Mediterranean Diet With No Restriction on Fat Intake: A Systematic Review and Meta-analysis.

Abstract

Background

Mediterranean diets may be healthier than typical Western diets.

Purpose

To summarize the literature comparing a Mediterranean diet with unrestricted fat intake with other diets regarding their effects on health outcomes in adults.

Data Sources

Ovid MEDLINE, CINAHL, and the Cochrane Library from 1990 through April 2016.

Study Selection

Controlled trials of 100 or more persons followed for at least 1 year for mortality, cardiovascular, hypertension, diabetes, and adherence outcomes, as well as cohort studies for cancer outcomes.

Data Extraction

Data extracted by 1 investigator was verified by another. Two reviewers assessed risk of bias and strength of evidence.

Data Synthesis

Two primary prevention trials found no difference in all-cause mortality between diet groups. One large primary prevention trial found that a Mediterranean diet resulted in a lower incidence of major cardiovascular events (hazard ratio [HR], 0.71 [95% CI, 0.56 to 0.90]), breast cancer (HR, 0.43 [CI, 0.21 to 0.88]), and diabetes (HR, 0.70 [CI, 0.54 to 0.92]). Pooled analyses of primary prevention cohort studies showed that compared with the lowest quantile, the highest quantile of adherence to a Mediterranean diet was associated with a reduction in total cancer mortality (risk ratio [RR], 0.86 [CI, 0.82 to 0.91]; 13 studies) and in the incidence of total (RR, 0.96 [CI, 0.95 to 0.97]; 3 studies) and colorectal (RR, 0.91 [CI, 0.84 to 0.98; 9 studies]) cancer. Of 3 secondary prevention studies reporting cardiovascular outcomes, 1 found a lower risk for recurrent myocardial infarction and cardiovascular death with the Mediterranean diet. There was inconsistent, minimal, or no evidence pertaining to any other outcome, including adherence, hypertension, cognitive function, kidney disease, rheumatoid arthritis, and quality of life.

Limitations

Few trials; medium risk-of-bias ratings for many studies; low or insufficient strength of evidence for outcomes; heterogeneous diet definitions and components.

Conclusion

Limited evidence suggests that a Mediterranean diet with no restriction on fat intake may reduce the incidence of cardiovascular events, breast cancer, and type 2 diabetes mellitus but may not affect all-cause mortality.

Primary Funding Source

Department of Veterans Affairs, Veterans Health Administration, Office of Research and Development, Quality Enhancement Research Initiative. (PROSPERO: CRD42015020262).

Links

  • Publisher Full Text
  • Authors+Show Affiliations

    ,

    From Center for Chronic Disease Outcomes Research, Minneapolis VA Health Care System, and University of Minnesota, Minneapolis, Minnesota.

    ,

    From Center for Chronic Disease Outcomes Research, Minneapolis VA Health Care System, and University of Minnesota, Minneapolis, Minnesota.

    ,

    From Center for Chronic Disease Outcomes Research, Minneapolis VA Health Care System, and University of Minnesota, Minneapolis, Minnesota.

    ,

    From Center for Chronic Disease Outcomes Research, Minneapolis VA Health Care System, and University of Minnesota, Minneapolis, Minnesota.

    ,

    From Center for Chronic Disease Outcomes Research, Minneapolis VA Health Care System, and University of Minnesota, Minneapolis, Minnesota.

    From Center for Chronic Disease Outcomes Research, Minneapolis VA Health Care System, and University of Minnesota, Minneapolis, Minnesota.

    Source

    Annals of internal medicine 165:7 2016 Oct 04 pg 491-500

    MeSH

    Arthritis, Rheumatoid
    Cardiovascular Diseases
    Cognition Disorders
    Dementia
    Diabetes Mellitus
    Diet, Mediterranean
    Dietary Fats
    Humans
    Mortality
    Neoplasms
    Primary Prevention
    Quality of Life
    Secondary Prevention

    Pub Type(s)

    Journal Article
    Meta-Analysis
    Review
    Systematic Review

    Language

    eng

    PubMed ID

    27428849

    Citation

    Bloomfield, Hanna E., et al. "Effects On Health Outcomes of a Mediterranean Diet With No Restriction On Fat Intake: a Systematic Review and Meta-analysis." Annals of Internal Medicine, vol. 165, no. 7, 2016, pp. 491-500.
    Bloomfield HE, Koeller E, Greer N, et al. Effects on Health Outcomes of a Mediterranean Diet With No Restriction on Fat Intake: A Systematic Review and Meta-analysis. Ann Intern Med. 2016;165(7):491-500.
    Bloomfield, H. E., Koeller, E., Greer, N., MacDonald, R., Kane, R., & Wilt, T. J. (2016). Effects on Health Outcomes of a Mediterranean Diet With No Restriction on Fat Intake: A Systematic Review and Meta-analysis. Annals of Internal Medicine, 165(7), pp. 491-500. doi:10.7326/M16-0361.
    Bloomfield HE, et al. Effects On Health Outcomes of a Mediterranean Diet With No Restriction On Fat Intake: a Systematic Review and Meta-analysis. Ann Intern Med. 2016 Oct 4;165(7):491-500. PubMed PMID: 27428849.
    * Article titles in AMA citation format should be in sentence-case
    TY - JOUR T1 - Effects on Health Outcomes of a Mediterranean Diet With No Restriction on Fat Intake: A Systematic Review and Meta-analysis. AU - Bloomfield,Hanna E, AU - Koeller,Eva, AU - Greer,Nancy, AU - MacDonald,Roderick, AU - Kane,Robert, AU - Wilt,Timothy J, Y1 - 2016/07/19/ PY - 2016/7/19/pubmed PY - 2017/5/6/medline PY - 2016/7/19/entrez SP - 491 EP - 500 JF - Annals of internal medicine JO - Ann. Intern. Med. VL - 165 IS - 7 N2 - Background: Mediterranean diets may be healthier than typical Western diets. Purpose: To summarize the literature comparing a Mediterranean diet with unrestricted fat intake with other diets regarding their effects on health outcomes in adults. Data Sources: Ovid MEDLINE, CINAHL, and the Cochrane Library from 1990 through April 2016. Study Selection: Controlled trials of 100 or more persons followed for at least 1 year for mortality, cardiovascular, hypertension, diabetes, and adherence outcomes, as well as cohort studies for cancer outcomes. Data Extraction: Data extracted by 1 investigator was verified by another. Two reviewers assessed risk of bias and strength of evidence. Data Synthesis: Two primary prevention trials found no difference in all-cause mortality between diet groups. One large primary prevention trial found that a Mediterranean diet resulted in a lower incidence of major cardiovascular events (hazard ratio [HR], 0.71 [95% CI, 0.56 to 0.90]), breast cancer (HR, 0.43 [CI, 0.21 to 0.88]), and diabetes (HR, 0.70 [CI, 0.54 to 0.92]). Pooled analyses of primary prevention cohort studies showed that compared with the lowest quantile, the highest quantile of adherence to a Mediterranean diet was associated with a reduction in total cancer mortality (risk ratio [RR], 0.86 [CI, 0.82 to 0.91]; 13 studies) and in the incidence of total (RR, 0.96 [CI, 0.95 to 0.97]; 3 studies) and colorectal (RR, 0.91 [CI, 0.84 to 0.98; 9 studies]) cancer. Of 3 secondary prevention studies reporting cardiovascular outcomes, 1 found a lower risk for recurrent myocardial infarction and cardiovascular death with the Mediterranean diet. There was inconsistent, minimal, or no evidence pertaining to any other outcome, including adherence, hypertension, cognitive function, kidney disease, rheumatoid arthritis, and quality of life. Limitations: Few trials; medium risk-of-bias ratings for many studies; low or insufficient strength of evidence for outcomes; heterogeneous diet definitions and components. Conclusion: Limited evidence suggests that a Mediterranean diet with no restriction on fat intake may reduce the incidence of cardiovascular events, breast cancer, and type 2 diabetes mellitus but may not affect all-cause mortality. Primary Funding Source: Department of Veterans Affairs, Veterans Health Administration, Office of Research and Development, Quality Enhancement Research Initiative. (PROSPERO: CRD42015020262). SN - 1539-3704 UR - https://www.unboundmedicine.com/medline/citation/27428849/full_citation L2 - https://www.annals.org/article.aspx?doi=10.7326/M16-0361 DB - PRIME DP - Unbound Medicine ER -