A study published in the Journal of Human Hypertension has shown that drinking hibiscus tea can reduce high blood pressure in people with type 2 diabetes. The study results showed the average systolic blood pressure for those drinking hibiscus tea decreased from 134.8 mmHg (17.97 kPa) at the beginning of the study to 112.7 mmHg (15.03 kPa) at the end of the study, one month later.
A study of 65 subjects published in 2009 found that 3 cups of hibiscus tea daily for 6 weeks reduced systolic blood pressure by 7 mm Hg in prehypertensive and mildly hypertensive participants. In those with mean systolic blood pressure over 129 mm Hg, the reduction was nearly 14 mm Hg. The study's lead author has noted that hibiscus flowers contain anthocyanins, which are believed to be the active antihypertensive compounds, acting as angiotensin-converting enzyme (ACE) inhibitors.
A study published in 2007 compared Hibiscus sabdariffa L. to the drug lisinopril on people with hypertension. Hibiscus "decreased blood pressure (BP) from 146.48/97.77 to 129.89/85.96 mmHg, reaching an absolute reduction of 17.14/11.97 mmHg (11.58/12.21%, p < 0.05)." Blood pressure "reductions and therapeutic effectiveness were lower than those obtained with lisinopril (p < 0.05)." The authors concluded that hibiscus "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." They attributed the blood pressure reducing effect of hibiscus to its diuretic effect and its ability to inhibit the angiotensin-converting enzyme through the presence of anthocyanins.
A 2004 study compared the effectiveness of hibiscus to the ACE-inhibiting drug captopril. The authors found that the "obtained data confirm that the H. sabdariffa extract, standardized on 9.6mg of total anthocyanins, and captopril 50 mg/day, did not show significant differences relative to hypotensive effect, antihypertensive effectiveness, and tolerability."
Source : http://en.wikipedia.org/wiki/Hibiscus_tea
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