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Eur J Clin Nutr. 2017 Sep;71(9):1033-1039. doi: 10.1038/ejcn.2017.55. Epub 2017 May 24.

Effects of supplementation with quercetin on plasma C-reactive protein concentrations: a systematic review and meta-analysis of randomized controlled trials.

Author information

1
Department of Clinical Nutrition, School of Nutrition and Food Sciences, Shiraz University of Medical Sciences, Shiraz, Iran.
2
Torbat Heydariyeh University of Medical Sciences, Torbat Heydariyeh, Iran.

Abstract

Promising experimental studies suggest that quercetin has potential anti-inflammatory effects. However, the results of current clinical trials on quercetin's effects on the C-reactive protein (CRP), a sensitive inflammatory biomarker, are ambiguous. We conducted a meta-analysis of available randomized controlled trials (RCTs) to resolve this inconsistency and quantify the net effect of quercetin on circulating CRP concentrations. A systematic search was performed in several databases including SCOPUS, PubMed-Medline and Google Scholar until 16 June 2016. We used a random-effects model in combination with weight mean difference (WMD) and 95% confidence intervals (CI) for data analysis. Standard methods were used for the assessment of heterogeneity, meta-regression, sensitivity analysis and publication bias. The meta-analysis of seven RCTs (10 treatment arms) showed a significant reduction of circulating CRP levels (WMD: -0.33 mg/l; 95% CI: -0.50 to -0.15; P<0.001) following quercetin supplementation. In the subgroup analysis, a significant reducing effect was observed in trials with ⩾500 mg/day dosage (WMD: -0.34 mg/l; 95% CI: -0.52, -0.16; P⩽0.001) and in those with CRP <3 mg/l (WMD: -0.34 mg/l; 95% CI: -0.51, -0.18; P⩽0.001). In meta-regression, there was no association between changes in CRP concentrations, dose of supplementation and CRP baseline values. Our findings showed a significant effect of quercetin supplementation on the C-reactive protein-especially at doses above 500 mg/day and in patients with CRP <3 mg/l.

PMID:
28537580
DOI:
10.1038/ejcn.2017.55
[Indexed for MEDLINE]

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