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Cited by 632Nutritional Studies and DietGlobal Cancer Incidence and ScreeningCancer Risks and Factors

Adherence to Mediterranean Diet and Risk of Cancer: An Updated Systematic Review and Meta-Analysis

Open access
Schwingshackl, Lukas, Schwedhelm, Carolina, Galbete, Cecilia, Hoffmann, Georg·2017·Nutrients
DOI 10.3390/nu9101063PMC PMC5691680
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Abstract

The aim of the present systematic review and meta-analysis was to gain further insight into the effects of adherence to Mediterranean Diet (MedD) on risk of overall cancer mortality, risk of different types of cancer, and cancer mortality and recurrence risk in cancer survivors. Literature search was performed using the electronic databases PubMed, and Scopus until 25 August 2017. We included randomized trials (RCTs), cohort (for specific tumors only incidence cases were used) studies, and case-control studies. Study-specific risk ratios, hazard ratios, and odds ratios (RR/HR/OR) were pooled using a random effects model. Observational studies (cohort and case-control studies), and intervention trials were meta-analyzed separately. The updated review process showed 27 studies that were not included in the previous meta-analysis (total number of studies evaluated: 83 studies). An overall population of 2,130,753 subjects was included in the present update. The highest adherence score to a MedD was inversely associated with a lower risk of cancer mortality (RRcohort: 0.86, 95% CI 0.81 to 0.91, I2 = 82%; n = 14 studies), colorectal cancer (RRobservational: 0.82, 95% CI 0.75 to 0.88, I2 = 73%; n = 11 studies), breast cancer (RRRCT: 0.43, 95% CI 0.21 to 0.88, n = 1 study) (RRobservational: 0.92, 95% CI 0.87 to 0.96, I2 = 22%, n = 16 studies), gastric cancer (RRobservational: 0.72, 95% CI 0.60 to 0.86, I2 = 55%; n = 4 studies), liver cancer (RRobservational: 0.58, 95% CI 0.46 to 0.73, I2 = 0%; n = 2 studies), head and neck cancer (RRobservational: 0.49, 95% CI 0.37 to 0.66, I2 = 87%; n = 7 studies), and prostate cancer (RRobservational: 0.96, 95% CI 0.92 to 1.00, I2 = 0%; n = 6 studies). Among cancer survivors, the association between the adherence to the highest MedD category and risk of cancer mortality, and cancer recurrence was not statistically significant. Pooled analyses of individual components of the MedD revealed that the protective effects appear to be most attributable to fruits, vegetables, and whole grains. The updated meta-analysis confirms an important inverse association between adherence to a MedD and cancer mortality and risk of several cancer types, especially colorectal cancer. These observed beneficial effects are mainly driven by higher intakes of fruits, vegetables, and whole grains. Moreover, we were able to report for the first time a small decrease in breast cancer risk (6%) by pooling seven cohort studies.

AI snapshot

Written from the paper’s full text.

TL;DR

This updated systematic review and meta-analysis found that highest adherence to a Mediterranean diet was inversely associated with overall cancer mortality and risk of several cancers, especially colorectal cancer. The protective associations appeared mainly driven by higher intakes of fruits, vegetables, and whole grains.

Key findings

  • Highest Mediterranean diet adherence was associated with lower overall cancer mortality (RRcohort 0.86, 95% CI 0.81–0.91; abstract reports I² = 82%, n = 14; Results report I² = 81%, n = 15) and lower colorectal cancer risk (RRobservational 0.82, 95% CI 0.75–0.88, I² = 73%, n = 11).
  • Inverse associations were also reported for breast cancer (RRobservational 0.92, 95% CI 0.87–0.96, I² = 22%, n = 16; RRRCT 0.43, 95% CI 0.21–0.88, n = 1), gastric cancer (RRobservational 0.72, 95% CI 0.60–0.86, I² = 55%, n = 4), liver cancer (RRobservational 0.58, 95% CI 0.46–0.73, I² = 0%, n = 2), head and neck cancer (RRobservational 0.49, 95% CI 0.37–0.66, I² = 87%, n = 7), and prostate cancer (RRobservational 0.96, 95% CI 0.92–1.00, I² = 0%, n = 6).
  • Among cancer survivors, the association between highest Mediterranean diet adherence and cancer mortality was not statistically significant (RR 0.95, 95% CI 0.82–1.12, I² = 5%, n = 4); cancer recurrence was also not statistically significant.
  • Pooled food-group analyses showed inverse associations for fruit (RR 0.93, 95% CI 0.89–0.97, I² = 60%, n = 13), vegetables (RR 0.96, 95% CI 0.93–0.98, I² = 0%, n = 14), whole grains (RR 0.91, 95% CI 0.87–0.95, I² = 31%, n = 9), and moderate alcohol consumption (RR 0.89, 95% CI 0.85–0.93); no significant associations were observed for cereals, dairy, fish, legumes, meat, nuts, or olive oil.

Methods

  • Updated systematic review and meta-analysis searching PubMed and Scopus until 25 August 2017, including RCTs, cohort studies, and case-control studies; 83 studies were included, of which 27 were new, with an overall population of 2,130,753 subjects.
  • The included evidence comprised two RCTs (4,887 subjects), 51 cohort studies (2,025,303 subjects), and 30 case-control studies (100,563 subjects).
  • Study-specific RRs, HRs, or ORs comparing highest vs. lowest Mediterranean diet adherence were pooled using a random-effects DerSimonian-Laird model; observational studies and intervention trials were meta-analyzed separately, with stratification by study design, heterogeneity assessed by Cochrane Q and I², and publication bias explored with Egger’s test and funnel plots when at least 10 studies were available.

Limitations

  • The paper states considerable heterogeneity, partly related to different Mediterranean diet definitions, adjustment factors, and heterogeneous study designs; high heterogeneity was observed for cancer mortality and colorectal cancer risk.
  • The paper states lopsided availability of studies by cancer type, few studies for several cancers, possible residual confounding, reliance on food frequency questionnaires, and that publication bias could not be completely excluded; most data came from US or European countries.
  • Evident from the text: the synthesis is dominated by observational studies, and the abstract and Results section report slightly different n/I² values for overall cancer mortality, indicating some inconsistency in reporting.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.3390/nu9101063

Cites

Statistics

Nothing to recompute.

Claims the paper makes

  • Findingown data

    In one randomized controlled trial, highest adherence to the Mediterranean diet was not significantly associated with overall cancer mortality (RR 0.75, 95% CI 0.17-3.33).

    “but not among one RCT (RRRCT: 0.75, 95% CI 0.17 to 3.33, I2 = NA)”
    Quote in the paperNot a substantial claim
  • Findingown data

    In case-control studies, high adherence to a Mediterranean dietary pattern was inversely associated with breast cancer risk (RR 0.89, 95% CI 0.85-0.94; I2 = 0%; n = 9 studies).

    “RRcase-control: 0.89, 95% CI 0.85 to 0.94, I2 = 0%, n = 9 studies)”
    Quote in the paperSubstantial claim
  • Findingown data

    In case-control studies, high adherence to a Mediterranean dietary pattern was inversely associated with risk of colorectal cancer (RR 0.71, 95% CI 0.57-0.88; I2 = 88%; n = 5 studies).

    “RRcase-control: 0.71, 95% CI 0.57 to 0.88, I2 = 88%, n = 5 studies)”
    Quote in the paperSubstantial claim
  • Findingown data

    In one randomized controlled trial, highest adherence to the Mediterranean diet was inversely associated with breast cancer risk (RR 0.43, 95% CI 0.21-0.88).

    “breast cancer (RRRCT: 0.43, 95% CI 0.21 to 0.88, I2 = NA%, n = 1 study;”
    Quote in the paperNot a substantial claim
  • Findingown data

    Among cancer survivors, highest adherence to the Mediterranean diet was not associated with risk of cancer mortality (RR 0.95, 95% CI 0.82-1.12; I2 = 5%; n = 4 studies).

    “Among cancer survivors, we observed no association between the adherence to the highest MedD category and risk of cancer mortality (RR: 0.95, 95% CI 0.82 to 1.12; I2 = 5%; n = 4 studies)”
    Quote in the paperNot a substantial claim
  • May combine two claims. 7
  • Classified as probably not a substantial claim. 3

  • May combine two claims.

    Findingown data

    No significant associations were observed between cancer risk and intakes of cereals, dairy, fish, legumes, meat, nuts, or olive oil.

    “No significant associations were observed for intakes of cereals, dairy, fish, legumes, meat, nuts, or olive oil (Figure 1).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The high levels of heterogeneity observed for colorectal cancer risk in the main analysis could not be confirmed for cohort studies in the stratified analysis, and were mainly driven by one large case-control study.

    “The high levels of heterogeneity observed for colorectal cancer risk in the main analysis could not be confirmed for cohort studies in the stratified analysis, and were mainly driven by one large case-control study.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    The review protocol of the previous versions of the systematic review is registered in PROSPERO.

    “The review protocol of the previous versions of the systematic review is registered in PROSPERO International Prospective Register of Systematic Reviews”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    A strength of the present study is the extensive literature research with strict adherence to quality standards set by PRISMA guidelines.

    “Strengths of the present study are the extensive literature research with strict adherence to quality standards set by PRISMA guidelines.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data

    The present update of the systematic review and meta-analyses provided additional important evidence for a beneficial effect of high adherence to the Mediterranean diet with respect to primary prevention of overall cancer risk and specific types of cancer, especially colorectal cancer.

    “In conclusion, the present update of our systematic review and meta-analyses provided additional important evidence for a beneficial effect of high adherence to MedD with respect to primary prevention overall cancer risk and specific types of cancer, especially colorectal cancer.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Study design and conductown data

    Egger's linear regression tests provided no evidence for publication bias for overall cancer mortality (p = 0.86), breast cancer (p = 0.39), and colorectal cancer (p = 0.14).

    “The Egger’s linear regression tests provided no evidence for a publication bias for overall cancer mortality (p = 0.86), breast cancer (p = 0.39), and colorectal cancer (p = 0.14), following comparison of the highest vs. lowest adherence to MedD category”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data

    Strongest adherence to a Mediterranean diet is inversely associated with cancer mortality and risk of colorectal, breast, gastric, liver, head and neck, gallbladder, and biliary tract cancer.

    “Following the synthesis of data from RCTs as well as cohort and case-control studies in the present systematic review, strongest adherence to a MedD was inversely associated with cancer mortality and risk of colorectal, breast, gastric, liver, head and neck, gallbladder, and biliary tract cancer.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    No significant associations were observed with respect to other types of cancer and for cancer survivors.

    “No significant associations could be observed with respect to other types of cancer and for cancer survivors.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).

    Interpretationcitation

    It remains difficult to define the Mediterranean diet as a distinct pattern.

    “However, it remains difficult to define the MedD as a distinct pattern.”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: The characteristics of the Mediterranean diet have changed considerably since the 1960s.
    • Rests on an assumption: Cutoff-points defined by medians vary between different populations.

  • May combine two claims.

    Study design and conductown data

    Funnel plots for risk of overall cancer mortality and risk of breast and colorectal cancer indicate moderate asymmetry, suggesting that publication bias cannot be completely excluded as a factor influencing the meta-analysis.

    “The funnel plots for risk of overall cancer mortality as well as risk of breast and colorectal cancer indicate moderate asymmetry, suggesting that publication bias cannot be completely excluded as a factor of influence on the present meta-analysis”
    Quote in the paperNot a substantial claim
10 of 10

  • The paper relies on this without support.

    The characteristics of the Mediterranean diet have changed considerably since the 1960s.

    “The characteristics of a MedD have changed considerably since the 1960s.”

  • The paper relies on this without support.

    Cutoff-points defined by medians vary between different populations.

    “It seems obvious that cutoff-points defined by medians vary between different populations, leading to an almost indefinite number of MedD subtypes.”
2 of 2

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • Greater adherence to the Mediterranean diet is associated with a significantly lower risk of cancer mortality, colorectal cancer, breast cancer, gastric cancer, liver cancer, head and neck cancer, and prostate cancer.

    “A meta-analysis including 2,130,753 participants concluded that greater adherence to MD was associated with a significantly lower risk of cancer mortality (RR 0.86; 95% CI 0.81 to 0.91), colorectal cancer (RR 0.82; 95% CI 0.75 to 0.88), breast cancer (RR 0.92; 95% CI 0.87 to 0.96), gastric cancer (RR 0.72; 95% CI 0.60 to 0.86), liver cancer (RR 0.58; 95% CI 0.46 to 0.73), head and neck cancer (RR”

    From Mediterranean Diet and Obesity-related Disorders: What is the Evidence? (2022) · cites this paper as [146]

  • High adherence to a Mediterranean diet was shown to reduce risk across all five NCDs by between 4% and 36%.

    “High adherence to a Mediterranean diet was shown to reduce risk across all five NCDs by between 4% and 36%,11,77,90,93,98”

    From Common risk factors for major noncommunicable disease, a systematic overview of reviews and commentary: the implied potential for targeted risk reduction (2019) · cites this paper as [93]

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Breast-cancer pooled estimate differs between abstract and Results

    Minor

    For the observational breast-cancer estimate of 0.92, the abstract gives a lower confidence limit of 0.87 and I2 of 22%, whereas the Results give 0.89 and 8%.

  • Cancer-mortality cohort analysis has conflicting study counts and heterogeneity

    Minor

    The abstract reports 14 cohort studies and I2 of 82%, while the Results report 15 studies and I2 of 81% for the same cohort estimate. The Results also state that cancer mortality was evaluated in 14 cohorts and one RCT, making the reported cohort count of 15 inconsistent with that breakdown.

2 of 2

The citation lists haven’t been fetched yet

References 162 · Cited by 632

Authors
Schwingshackl, L., Schwedhelm, C., Galbete, C., & Hoffmann, G.
Affiliations
  • German Institute of Human Nutrition (DE)
  • University of Vienna (AT)
Corresponding author
Schwingshackl, Lukas
ORCID
Venue
Nutrients
Publisher
MDPI AG
Published
2017-09-26
Volume
9
Issue
10
Pages
1063
ISSN
2072-6643 (ISSN-L)
DOI
10.3390/nu9101063
PMC
PMC5691680
OpenAlex
W2757435464
Cited by
632
References
162
Citations by year
2026: 39 · 2025: 60 · 2024: 71 · 2023: 72 · 2022: 91 · 2021: 91 · 2020: 93 · 2019: 69 · 2018: 44 · 2017: 1
FWCI
9.19
Type
journal article
Language
en
Open access
Licence
Locations
  • Nutrients (publishedVersion, cc-by)
  • Europe PMC (PubMed Central) (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • eRepository Mondragon University (Mondragon University) (submittedVersion, cc-by)
  • Phaidra (Universität Wien) (submittedVersion, cc-by-nc-nd)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
Topics
  • Health Sciences › Medicine › Public Health, Environmental and Occupational Health › Nutritional Studies and Diet
  • Health Sciences › Medicine › Oncology › Global Cancer Incidence and Screening
  • Health Sciences › Medicine › Oncology › Cancer Risks and Factors
Keywords
Mediterranean diet, diet and cancer risk, cancer mortality, colorectal cancer, breast cancer, gastric cancer, liver cancer, head and neck cancer, prostate cancer, tumor recurrence, cancer survivors, dietary adherence, cancer prevention, cancer survivorship, cancer survivorship quality of life, survivorship care, cancer survivorship support services
MeSH terms
Whole Grains, Diet, Healthy, Adult, Aged, Aged, 80 and over, Female, Fruit, Humans, Male, Middle Aged, Neoplasms, Patient Compliance, Risk Factors, Time Factors, Vegetables, Odds Ratio, Risk Assessment, Diet, Mediterranean, Risk Reduction Behavior, Protective Factors

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