Abstract
INTRODUCTION: Many experimental and clinical trials have suggested that flaxseed might be a potent antihypertensive, but the evidence concerning the effects of flaxseed supplements on plasma C-reactive protein (CRP) concentrations has not been fully conclusive. We assessed the impact of the effects of flaxseed supplementation on plasma CRP concentrations through a systematic review of literature and meta-analysis of available randomised controlled trials (RCTs). MATERIAL AND METHODS: The literature search included EMBASE, ProQuest, CINAHL, and PUBMED databases up to 1(st) February 2016 to identify RCTs investigating the effect of flaxseed supplements on plasma CRP concentrations. Meta-analysis was performed using a random-effects model, and effect size was expressed as weighed mean difference (WMD) and 95% confidence interval (CI). RESULTS: Meta-analysis of 17 selected RCTs with 1256 individuals did not suggest a significant change in plasma CRP concentrations following supplementation with flaxseed-containing products (WMD: -0.25 mg/l, 95% CI: -0.53, 0.02, p = 0.074). The effect size was robust in the leave-one-out sensitivity analysis. Subgroup analysis did not suggest any significant difference in terms of changing plasma CRP concentrations among different types of flaxseed supplements used in the included studies, i.e. flaxseed oil (WMD: -0.67 mg/l, 95% CI: -2.00, 0.65, p = 0.320), lignan extract (WMD: -0.32 mg/l, 95% CI: -0.71, 0.06, p = 0.103) and ground powder (WMD: -0.18 mg/l, 95% CI: -0.42, 0.06, p = 0.142). CONCLUSIONS: The meta-analysis of RCTs did not show a significant change in plasma CRP concentrations following supplementation with various flaxseed products. Large, well-designed studies should be still performed to validate the current results.