The Role of Hibiscus Tea in Reducing High Blood Pressure

Hibiscus tea is made from the Hibiscus sabdariffa flower, which has been used in folk medicine as a diuretic and for the treatment of several other complaints, including high blood pressure, liver diseases and fever. The pharmacological actions of the Hibiscus sabdariffa extracts include strong in vitro and in vivo antioxidant activity.

Studies have shown that consuming hibiscus tea infusion has positive effects on blood pressure. High blood pressure (hypertension) is defined as having a systolic and diastolic blood pressure greater than 140 and 90 mmHg. Systolic pressure is the pressure when the heart beats while pumping blood and diastolic pressure is the pressure in large arteries when the heart is at rest between beats.

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A double-blind randomized controlled trial involving 60 type II diabetes patients with mild hypertension showed that consuming hibiscus tea infusion has positive effects on blood pressure. The patients were randomly allocated to hibiscus tea (HT) and black tea (BT) groups and instructed to drink HT and BT infusions twice a day for 1 month. Their blood pressure was measured on days 0, 15 and 30 of the study. The mean of systolic blood pressure in the HT group decreased from 134.4+/-11.8 mm Hg at the beginning of the study to 112.7+/-5.7 mm Hg after 1 month, whereas this measure increased from 118.6+/-14.9 to 127.3+/-8.7 mm Hg in the BT group during the same period. The intervention had no statistically significant effect on the mean of diastolic blood pressure in either the HT or BT group. The mean pulse pressure of the patients in the HT group decreased from 52.2+/-12.2 to 34.5+/-9.3 mm Hg during the study, whereas in the BT group, it increased from 41.9+/-11.7 to 47.3+/-9.6 mm Hg.

A controlled and randomized clinical trial involving 75 patients with mild to moderate hypertension was conducted to compare the antihypertensive effectiveness and tolerability of a standardized extract from Hibiscus sabdariffa with captopril, a medication used for the treatment of high blood pressure, but with numerous adverse side effects. The study consisted of the administration of 10g hibiscus tea (standardized on 9.6mg of total anthocyanins) infusion daily before breakfast, or captopril 25 mg twice a day, for 4 weeks. The results showed that H. sabdariffa was able to decrease the systolic blood pressure from 139.05 to 123.73mm Hg and the diastolic blood pressure from 90.81 to 79.52mm Hg. There were no significant differences relative to hypotensive effect, antihypertensive effectiveness, and tolerability between the H. sabdariffa extract and captopril 50 mg/day.

Pharmacological work has demonstrated that the antihypertensive effect of Hibiscus sabdariffa is probably produced by a diuretic activity and inhibition of the angiotensin-converting enzyme (ACE). A randomized, controlled, and double-blind clinical trial was conducted on 193 patients with high blood pressure that compared therapeutic effectiveness, tolerability, and safety, as well as the effect on serum electrolytes and the ACE inhibitory effect of a herbal medicinal product prepared from the dried extract of Hibiscus sabdariffa with those of lisinopril, a medication used for the treatment of high blood pressure. Patients with hypertension stage I or II were treated daily for 4 weeks with the Hibiscus sabdariffa, 250 mg of total anthocyanins per dose, or 10 mg of lisinopril. The H. sabdariffa exerted important antihypertensive effectiveness with a wide margin of tolerability and safety, while it also significantly reduced plasma ACE activity and demonstrated a tendency to reduce serum sodium (Na) concentrations without modifying potassium (K) levels.
References:
1. Mozaffari-Khosravi H, Jalali-Khanabadi BA, Afkhami-Ardekani M, Fatehi F, Noori-Shadkam M. The effects of sour tea (Hibiscus sabdariffa) on hypertension in patients with type II diabetes. J Hum Hypertens. 2009 Jan;23(1):48-54. Epub 2008 Aug 7. PMID: 18685605.
2. Herrera-Arellano A, Flores-Romero S, Chávez-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. 2004 Jul;11(5):375-82. PMID: 15330492.
3. Herrera-Arellano A, et al. Clinical effects produced by a standardized herbal medicinal product of Hibiscus sabdariffa on patients with hypertension. A randomized, double-blind, lisinopril-controlled clinical trial. Planta Med. 2007 Jan;73(1):6-12. PMID: 17315307.
4. Ali BH, Al Wabel N, Blunden G. Phytochemical, pharmacological and toxicological aspects of Hibiscus sabdariffa L.: a review. Phytother Res. 2005 May;19(5):369-75. PMID: 16106391.