The Effect of Cranberry Consumption on C-Reactive Protein and Interleukin-6: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Abstract

Previous clinical trials examining the effects of cranberry on inflammatory markers have yielded inconsistent results. This study specifically aimed to assess the influence of cranberry consumption on C-reactive protein (CRP) and Interleukin-6 in randomized controlled trials (RCTs). A thorough systematic review was conducted by searching ISI Web of Science, Cochrane Library, PubMed, Scopus, and Google Scholar up to December 21, 2024, with no language restrictions applied, by two independent authors. The results were synthesized using the DerSimonian and Laird random-effects model. From an initial pool of 1882 articles, 10 were selected for the systematic review and meta-analysis. The findings indicated that cranberry did not significantly influence CRP (weighted mean differences (WMD): 0.01 mg/L; 95 CI: -0.38 to 0.40, p = 0.95; I 2: 80.8) or Interleukin-6 (WMD: -0.26 pg/mL; 95 CI: -1.78 to 1.27, p = 0.74; I 2: 86.1). However, it was observed that cranberry consumption was associated with a significant rise in CRP levels in obese individuals or in studies focused solely on women. Furthermore, research showed that the active ingredient in cranberry, when administered in powder form, could lead to a considerable increase in interleukin-6 levels. This review and meta-analysis suggest that cranberry supplementation did not affect CRP or Interleukin-6 levels. To further assess and validate these results, more long-term and well-designed RCTs are needed.