This study compared the effectiveness and tolerability of hibiscus sabdariffa versus captopril in 90 patients with mild to moderate hypertension. Participants were given either 10g of hibiscus in water (hibiscus tea) before breakfast or two captopril capsules (25g) each day for four weeks. Both groups saw the same results, a reduction of systolic and diastolic blood pressure of slightly more than 10%. (Average systolic decreased from 139.05 to 123.73 and diastolic from 90.81 to 79.52 in the hibiscus group.) Tolerance was the same for both groups.

The amount taken by participants corresponds to roughly 4 teaspoons of hibiscus per cup of tea (10g = 4 x 2.5g per teaspoon average).

References:

1. Herrera-Arellano A, Flores-Romero S, Chavez-Soto MA, Tortoriello J., "Effectiveness and tolerability of a standardized extract from Hibiscus sabdariffa in patients with mild to moderate hypertension: a controlled and randomized clinical trial," Phytomedicine, Jul 2004