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Garlic consumption and cancer prevention: meta-analyses of colorectal and stomach cancers.

Abstract

BACKGROUND

Animal and in vitro studies have provided evidence of an anticarcinogenic effect of active ingredients in garlic.

OBJECTIVE

The objective was to conduct meta-analyses of the epidemiologic literature on the association between garlic consumption and risk of stomach, colon, head and neck, lung, breast, and prostate cancers.

DESIGN

Meta-analyses were conducted for all cancers mutually and separately for colorectal and stomach cancers in relation to consumption of exclusively raw garlic, cooked garlic, or both (RC garlic). Eighteen studies reported a relative risk estimate for RC garlic consumption and cancer risk.

RESULTS

In the meta-analyses of colorectal and stomach cancer, the reference categories ranged from no consumption to consumption of 3.5 g/wk, whereas the highest categories ranged from any consumption to >28.8 g/wk. The average difference between the highest and lowest categories was 16 g/wk. The random-effects relative risk (RR) estimate of colorectal cancer and RC garlic consumption, excluding garlic supplements, was 0.69 (95% CI: 0.55, 0.89). For stomach cancer, the random-effects RR estimate was 0.53 (95% CI: 0.31, 0.92). The heterogeneity among studies for the latter outcome (P: = 0.0002) indicates the questionableness of the generalizability of this summary estimate. An indication of publication bias for all cancers combined is evident from a funnel plot of RC garlic consumption and cancer risk and from the results of the Begg and Mazumdar test (P: = 0.049).

CONCLUSIONS

High intake of RC garlic may be associated with a protective effect against stomach and colorectal cancers. Heterogeneity of effect estimates, differences in dose estimation, publication bias, and possible alternative hypotheses (eg, confounding by total vegetable consumption) preclude sole reliance on summary effect estimates.

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  • Authors+Show Affiliations

    ,

    Departments of Epidemiology and Nutrition, University of North Carolina, Chapel Hill, NC 27599, USA.

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    Source

    MeSH

    Breast Neoplasms
    Colorectal Neoplasms
    Female
    Garlic
    Head and Neck Neoplasms
    Humans
    Lung Neoplasms
    MEDLINE
    Male
    Plants, Medicinal
    Prostatic Neoplasms
    Publication Bias
    Stomach Neoplasms

    Pub Type(s)

    Journal Article
    Meta-Analysis
    Research Support, U.S. Gov't, P.H.S.

    Language

    eng

    PubMed ID

    11010950

    Citation

    Fleischauer, A T., et al. "Garlic Consumption and Cancer Prevention: Meta-analyses of Colorectal and Stomach Cancers." The American Journal of Clinical Nutrition, vol. 72, no. 4, 2000, pp. 1047-52.
    Fleischauer AT, Poole C, Arab L. Garlic consumption and cancer prevention: meta-analyses of colorectal and stomach cancers. Am J Clin Nutr. 2000;72(4):1047-52.
    Fleischauer, A. T., Poole, C., & Arab, L. (2000). Garlic consumption and cancer prevention: meta-analyses of colorectal and stomach cancers. The American Journal of Clinical Nutrition, 72(4), pp. 1047-52.
    Fleischauer AT, Poole C, Arab L. Garlic Consumption and Cancer Prevention: Meta-analyses of Colorectal and Stomach Cancers. Am J Clin Nutr. 2000;72(4):1047-52. PubMed PMID: 11010950.
    * Article titles in AMA citation format should be in sentence-case
    TY - JOUR T1 - Garlic consumption and cancer prevention: meta-analyses of colorectal and stomach cancers. AU - Fleischauer,A T, AU - Poole,C, AU - Arab,L, PY - 2000/9/30/pubmed PY - 2000/10/21/medline PY - 2000/9/30/entrez SP - 1047 EP - 52 JF - The American journal of clinical nutrition JO - Am. J. Clin. Nutr. VL - 72 IS - 4 N2 - BACKGROUND: Animal and in vitro studies have provided evidence of an anticarcinogenic effect of active ingredients in garlic. OBJECTIVE: The objective was to conduct meta-analyses of the epidemiologic literature on the association between garlic consumption and risk of stomach, colon, head and neck, lung, breast, and prostate cancers. DESIGN: Meta-analyses were conducted for all cancers mutually and separately for colorectal and stomach cancers in relation to consumption of exclusively raw garlic, cooked garlic, or both (RC garlic). Eighteen studies reported a relative risk estimate for RC garlic consumption and cancer risk. RESULTS: In the meta-analyses of colorectal and stomach cancer, the reference categories ranged from no consumption to consumption of 3.5 g/wk, whereas the highest categories ranged from any consumption to >28.8 g/wk. The average difference between the highest and lowest categories was 16 g/wk. The random-effects relative risk (RR) estimate of colorectal cancer and RC garlic consumption, excluding garlic supplements, was 0.69 (95% CI: 0.55, 0.89). For stomach cancer, the random-effects RR estimate was 0.53 (95% CI: 0.31, 0.92). The heterogeneity among studies for the latter outcome (P: = 0.0002) indicates the questionableness of the generalizability of this summary estimate. An indication of publication bias for all cancers combined is evident from a funnel plot of RC garlic consumption and cancer risk and from the results of the Begg and Mazumdar test (P: = 0.049). CONCLUSIONS: High intake of RC garlic may be associated with a protective effect against stomach and colorectal cancers. Heterogeneity of effect estimates, differences in dose estimation, publication bias, and possible alternative hypotheses (eg, confounding by total vegetable consumption) preclude sole reliance on summary effect estimates. SN - 0002-9165 UR - https://www.unboundmedicine.com/medline/citation/11010950/full_citation L2 - https://academic.oup.com/ajcn/article-lookup/doi/10.1093/ajcn/72.4.1047 DB - PRIME DP - Unbound Medicine ER -