Results of a small randomized trial show that 3 cups of hibiscus tea
daily for 6 weeks reduced systolic blood pressure (SBP) by about 7
mm Hg in prehypertensive and mildly hypertensive subjects.

Among those with SBP over the median of 129 mm Hg, the reduction was
double that, almost 14 mm Hg after 6 weeks, and produced significant
reductions in diastolic and mean arterial pressures.

The finding "suggests that regularly incorporating hibiscus tea into
the diet may actually help control blood pressure in people who are
at risk for developing hypertension," said lead author Diane L.
McKay, PhD, from the Jean Mayer USDA Nutrition Research Center on
Aging at Tufts University, in Boston, Massachusetts, at a press
conference here.

On a population basis, even small changes such as those seen in this
study would be expected to reduce stroke, coronary artery disease,
and all-cause mortality, Dr. McKay added.

The findings of this trial, which was supported by the Agricultural
Research Service of the United States Department of Agriculture
(USDA) and by Hain Celestial Group, makers of the Celestial
Seasonings brand of herbal teas, were presented here at the American
Heart Association 2008 Scientific Sessions.

Bioactive Phytochemicals

Hibiscus is among the most common ingredients found in herbal tea
blends sold in the United States, Dr. McKay said. The principal
components of hibiscus include anthocyanins and other flavanoids, as
well as polyphenolic compounds and phenolic acids.

A variety of bioactivities have been attributed to these compounds,
she noted, including the ability to act as an angiotensin-
converting”Venzyme (ACE) inhibitor. Earlier short-term trials in
humans used black tea as a control, which also has an effect on
vascular reactivity, making it not a proper control to look at the
effects of hibiscus tea, she pointed out. "It is also interesting to
note that a study comparing hibiscus tea with captopril, an ACE
inhibitor, found no difference in blood pressure”Vlowering effects."

The aim of their study, she said, was to determine whether hibiscus
tea, "in an amount that can be readily incorporated into the diet,"
will lower blood pressure in prehypertensive and mildly hypertensive
adults compared with a placebo beverage.

The study was a randomized, double-blind, placebo-controlled trial
of 65 generally healthy men and women aged 30 to 70 years who had
SBP readings of 120 to 150 mm Hg and a diastolic blood pressure
(DBP) of < 95 mm Hg.

Subjects were not taking antihypertensive medications or other
supplements or medications that could affect their blood pressure
level. They were not excluded on the basis of body-mass index (BMI),
and BMIs in the study ranged from 18.5 to 34.9.

Participants were randomized to receive either three 8-oz servings
daily of hibiscus tea for 6 weeks or a placebo beverage. The
hibiscus tea was prepared by brewing 1 tea bag containing 1.25 g of
dried hibiscus calyces in 8 oz of boiled water for 6 minutes, after
which the tea bag was removed. The placebo beverage was prepared by
adding a small amount of hibiscus-flavored concentrate to 8 oz of
water.

The beverage had to be consumed within 12 hours of preparation and
could be served hot or cold and with or without milk and a sweetener
of the subjects' choice, she noted. The placebo beverage had no
anthocyanins, which they believe is the active component, Dr. McKay
pointed out.

Outcomes of interest were the change from baseline in SBP, DBP, and
mean arterial pressure (MAP).

"After 6 weeks, we found that subjects who consumed hibiscus tea had
a significantly lower systolic blood pressure level compared with
people in the placebo group," said Dr. McKay. A drop in DBP and MAP
was also seen, but these changes were not significantly different
from placebo.

However, in a subgroup analysis of subjects with systolic pressures
higher than 129 mm Hg, the magnitude of the change found with
hibiscus tea was almost double that seen in the overall group, and
differences with placebo with regard to systolic, diastolic and mean
arterial pressure were all statistically significant, Dr. McKay
said.

Dr. McKay put their findings into the context of previously
published work suggesting that, on a population basis, a reduction
of 3 mm Hg in systolic blood pressure would be expected to translate
into a reduction in stroke mortality of 8%, of 5% in coronary heart
disease mortality, and of 4% in all-cause mortality (Whelton PK et
al. JAMA. 2002;288:1882-1888).

During her presentation, she was asked by an audience member about
any potential adverse events from this amount of hibiscus tea.

No adverse effects were reported, she responded. "There are some
data from Nigeria, where we know that the average per capita
consumption of a hibiscus-containing beverage is about the
equivalent to 25 cups of our hibiscus tea every day, and no adverse
effects have been demonstrated."

The study was funded by the Agricultural Research Service of the
USDA and by Hain Celestial Group. The authors report no disclosures.


American Heart Association 2008 Scientific Sessions: Abstract 3278.
Presented November 10, 2008.