NEW ORLEANS — Quaffing three cups of hibiscus tea daily for 6 weeks resulted in a mean 7.2-mm Hg reduction in systolic blood pressure in mildly hypertensive or prehypertensive adults in a randomized, double-blind, placebo-controlled trial.
“This suggests regularly incorporating hibiscus tea into the diet may help control blood pressure in people at risk of developing hypertension,” Diane L. McKay, Ph.D., concluded at the annual scientific sessions of the American Heart Association.
The public health implications of a blood pressure reduction of this magnitude, if extended to a large population, could be profound.
The National High Blood Pressure Education Program Coordinating Committee has estimated that a mere 3-mm Hg reduction in systolic blood pressure (SBP) would reduce the relative risk death due to stroke by 8%, death due to coronary artery disease by 5%, and all-cause mortality by 4% (JAMA 2002;288:1882–8), noted Dr. McKay, of the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, Boston.
She reported findings on 65 prehypertensive or mildly hypertensive adults who took part in a 6-week double-blind study in which they consumed three 8-ounce cups of hibiscus tea daily or a placebo beverage similar in color and taste.
Mean SBP dropped by 7.2 mm Hg in the herbal tea group from a baseline of 129.4 mm Hg, compared with a 1.3-mm Hg decline in the control group. Diastolic blood pressure (DBP) fell by a mean of 3.1 mm Hg from a baseline of 78. 9 mm Hg and mean arterial pressure dropped by 4.5 mm Hg from 95.7 mm Hg at enrollment, although neither of these changes achieved statistical significance.
However, the herbal tea's antihypertensive effect was greater in patients with higher baseline blood pressure, Dr. McKay reported.
Among the half of participants whose SBP exceeded 129 mm Hg, the mean SBP reduction after 6 weeks of hibiscus tea consumption was 13.2 mm Hg, and the reductions of 6.4 mm Hg in DBP and 8.7 mm Hg in mean arterial pressure were also statistically significant, she said.
The intervention had no side effects or downsides. The participants found it easy to work consumption of three cups of tea into their daily life, Dr. McKay continued.
Dr. Robert H. Eckel observed that the blood pressure reduction seen with hibiscus tea in this trial is equal in size to the typical effect of a single antihypertensive medication. But he added that while the notion of hibiscus tea as a nutraceutical for blood pressure lowering is intriguing, a larger confirmatory study with longer follow-up is needed.
“At this point, to make a nutritional recommendation with these data would be far premature. Nevertheless, this is interesting,” commented Dr. Eckel, who is past president of the AHA and professor of medicine, physiology, and biophysics and program director of the adult general clinical research center at the University of Colorado, Denver.
Dr. McKay and her coworkers conducted their randomized trial because earlier animal studies had suggested that Hibiscus sabdariffa L. has antihypertensive and antiatherosclerotic effects. Hibiscus contains flavinoids and phenolic acids that have potent antioxidant properties.
The study was supported by the Agricultural Research Service of the U.S. Department of Agriculture and by Celestial Seasonings.
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Hibiscus tea cut blood pressure as much as a single antihypertensive drug. ©Monika Adamczyk/Fotolia.com