It’s always gratifying when a simple, safe, inexpensive herb proves useful for a common medical problem. To wit, consider hibiscus, which, according to a recent study, is very good for reducing blood pressure in hypertensive people.
Hibiscus flowers have been used historically to treat high blood pressure, liver disease, and fever for centuries, and it turns out that in addition to ascorbic and citric acid (vitamin C), they contain a number of important vasoactive alkaloids, anthocyanins and quercetin.
The current study was designed to compare the blood pressure lowering effects of “Sour tea,” made from Hibiscus sabdariffa, with ordinary black tea (Camellia sinensis) in type II diabetics with mild high blood pressure, as defined by JNC-VI diagnostic criteria.
Sixty such patients, none of whom were taking antihypertensive or lipid-lowering medications, were randomly assigned to drink one cup of Sour tea or black tea twice daily for one month. Each infusion was to be made with one tea sachet weighing 2 gm, placed in a tea pot with 240 ml boiling water, and steeped for 20-30 minutes. They were permitted to add one cube of sugar.
The average systolic blood pressure (SBP) in the Hibiscus group decreased from 134.4 ± 11.8 mmHg at baseline to 112.7 ± 5.7 mmHg after 1 month, a robust 16% reduction, a 7.3% rise. Among the black tea drinkers, the average SBP actually increased over the month, from 118.6 ± 14.9 mmHg at baseline to 127.3 ± 8.7 mmHg. There were no statistically significant changes in mean diastolic blood pressure in either group.
The mean pulse pressure decreased from 52.2+/-12.2 to 34.5+/-9.3 mmHg among the Hibiscus drinkers, whereas in the black tea group, it increased from 41.9+/-11.7 to 47.3+/-9.6 mmHg. Overall, the interventions were deemed “effective” (ie. producing significant decreases in systolic pressure) in 48% of the sour tea patients but only 15% of the black tea patients (Mozaffari-Khosravi H, et al. J Human Hypertension 2009;23:48-54).
The fact that there was a large, nearly 16 mmHg difference in the baseline mean systolic pressures between the two treatment groups, does raise a methodological red flag, and the authors acknowledge that the study design would have been stronger had it included a third group that drank no tea at all.
None the less, the findings are highly supportive of Hibiscus as a remedy for mild blood pressure elevations, in which the risks and costs of drug therapy may not be outweighed by their expected benefits, or in cases where a patient is categorically opposed to pharmaceutical treatment.
The study is also good news for hypertensive patients from tea-loving cultures, including those from Asia, Latin America, and the Middle East, where Hibiscus is a common and well-loved herbal tea.
