We aimed to assess the efficacy of Hibiscus sabdariffa in patients with mild-to-moderate hypertension or metabolic syndrome (MetS) by comparing it against placebo, antihypertensive drugs, or other herbal products. Four databases were searched for randomized clinical trials (RCTs) examining the efficacy of H. sabdariffa in patients with mild-to-moderate hypertension or hypertension associated with MetS. Data on the change in systolic blood pressure (SBP) and diastolic blood pressure (DBP) were extracted and analyzed using Review Manager Version 5.3. A total of 13 RCTs (1205 participants) were analyzed. Hibiscus sabdariffa significantly reduced both SBP and DBP compared with placebo (mean difference -6.67, P = 0.004 and -4.35 mm Hg, P = 0.02). Subgroup analysis showed that change in SBP and DBP was statistically significant in patients with only hypertension, whereas not significant in patients with hypertension associated with MetS. When H. sabdariffa was compared with active controls (antihypertensive drugs or other herbals), the change in SBP and DBP was not statistically significant (all P > 0.05). Hibiscus sabdariffa is effective in reducing the SBP and DBP in patients with mild-to-moderate hypertension, but was neither effective in those with MetS nor superior to antihypertensive drugs. Further RCTs are required to determine the long-term efficacy of H. sabdariffa and to describe patients who would benefit most from this treatment.
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