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Original research
Effect of garlic intake on inflammatory mediators: a systematic review and meta-analysis of randomised controlled trials
  1. Mehdi Koushki1,
  2. Nasrin Amiri-Dashatan2,
  3. Yasin Pourfarjam3,
  4. Amir Hossein Doustimotlagh4
  1. 1 Department of Clinical Biochemistry, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran
  2. 2 Proteomics Research Center, Faculty of Paramedical Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran
  3. 3 Department of Chemistry, University of Cincinnati, Cincinnati, Ohio, USA
  4. 4 Medicinal Plants Research Center, Yasuj University of Medical Sciences, Yasuj, Iran
  1. Correspondence to Dr Amir Hossein Doustimotlagh, Medicinal Plants Research Center, Yasuj University of Medical Sciences, Yasuj, Iran; amirhosseindoustimotlagh{at}gmail.com

Abstract

Background Garlic is a species in the onion genus, Allium. Data have shown that garlic has anti-inflammatory activity; however, the findings are inconclusive and inconsistent. We aimed to evaluate the impact of garlic intake on inflammatory mediators through systematic review and meta-analysis of existing data.

Methods Electronic databases were completely investigated using databases of ISI Web of Science, Medline, Scopus, Cochrane Library and EMBASE until October 2019. A random effects model and the generic reverse variance procedure were used for quantitative data production. Sensitivity analyses and prespecified subgroup were done to evaluate potential heterogeneity. Random effect meta-regression was conducted to investigate the effects of possible confounders on the assessed effect size.

Results Ten trials with one observational study, including 530 participants, met the eligibility criteria. The findings showed reduction in the tumour necrosis factor alpha (TNF-α) (−0.31 pg/mL, 95% CI −1.07 to 0.46) and C reactive protein (CRP) levels (−0.20 mg/L, 95% CI −1.4 to 1.05) following supplementation with garlic, although it had no marked impact on the interleukin 6 (IL-6) level (0.37 pg/mL, 95% CI −0.58 to 1.33). In the subgroup analysis, we found that garlic supplementation significantly decreased TNF-α, highly sensitive CRP and IL-6 levels in subgroups of >8, >6 and ≥4 weeks of intervention duration, respectively, and dose of garlic consumption between 2 and 2.4 g/day.

Conclusion These findings suggested that current evidence may support garlic as an adjunct to pharmacological management of metabolic diseases.

PROSPERO registration number CRD42018108816.

  • garlic
  • inflammatory cytokines
  • meta-analysis
  • TNF-α
  • CRP

http://dx.doi.org/10.1136/postgradmedj-2019-137267

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    Footnotes

    • Contributors MK, AHD and NA-D conceptualised and designed the research. YP and AHD critically reviewed the manuscript and approved the final manuscript as submitted. MK, NA-D and AHD wrote the draft of this paper and were responsible for the data collection, statistical analyses and data interpretation.

    • Funding This work was supported by grant (IR.YUMS.REC.1397.082) from the Deputy of Research, Yasuj University of Medical Sciences.

    • Competing interests None declared.

    • Patient consent for publication Not required.

    • Ethics approval Ethical approval will not be applied for because of the relevant data we extracted which does not involve any individual privacy.

    • Provenance and peer review Not commissioned; externally peer reviewed.

    • Data availability statement Data are available in a public, open access repository. Data of this study are included in the article and the primary data can be provided from the corresponding author.