Hibiscus sabdariffa L. tea (tisane) lowers blood pressure in prehypertensive and mildly hypertensive adults.

Placebo-controlled intervention study in nonsmoking adults aged 30 to 70 years with prehypertension or mild hypertension who were not taking blood pressure-lowering medications. Participants were recruited from the greater Boston area; the active hibiscus tea arm included 35 participants.

In the hibiscus tea group, participants consumed 3 servings per day (720 mL/day) for 6 weeks. Each 240 mL serving was prepared by brewing 1 tea bag containing 1.25 g of Hibiscus sabdariffa for 6 minutes; the comparison beverage was a placebo flavored to resemble hibiscus tea.

Hibiscus tea lowered systolic blood pressure more than placebo over 6 weeks. Mean SBP fell from 129.4 +/- 4.8 to 122.3 +/- 10.3 mm Hg in the hibiscus group versus 129.8 +/- 6.9 to 128.6 +/- 10.6 mm Hg in the placebo group, for a between-group P = 0.030. Diastolic blood pressure did not differ clearly from placebo (change -3.1 +/- 7.0 vs -0.5 +/- 7.5 mm Hg, P = 0.160), although the hibiscus group showed within-group improvements in SBP, DBP, and MAP. Greater baseline SBP was associated with a larger SBP reduction (r = -0.421, P = 0.010), supporting a stronger effect in participants with higher starting systolic pressure.

The active intervention arm was small, with only 35 participants, and treatment lasted just 6 weeks. The sample was limited to nonsmoking adults with prehypertension or mild hypertension from one geographic area, which may limit generalizability. Ethnicity data, adverse events, and longer-term outcomes were not reported in the extracted source.