"Hibiscus Tea vs. Plant-Based Diets for Hypertension
& How Much Hibiscus Tea Is Too Much?" The latest research pitted
hibiscus against obesity, giving hibiscus to overweight individuals,
and showed reduced body weight, but after 12 weeks on hibiscus
they only lost like 3 pounds, and really only one and
a half pounds over placebo— clearly no magic fix. The purported cholesterol-lowering
property of hibiscus tea had looked a bit
more promising. Some older studies suggested
as much as an 8% reduction drinking two cups
a day for a month, but when all the studies are put together
the results were pretty much a wash. This may be because only about
50% of people respond at all to drinking the equivalent of
between 2 to 5 cups a day, though those that do respond may get a
respectable 12 or so percent drop in cholesterol, but nothing like the
30% drop one can get within weeks of eating a
healthy enough plant-based diet.
High blood pressure is where
hibiscus may really shine, a disease affecting a billion
people, killing millions. Up until 2010, there wasn’t sufficient
high quality research out there to support the use of
hibiscus tea to treat it, but there are now randomized double-blind,
placebo-controlled studies where hibiscus tea is compared to
artificially colored and flavored water that looks and tastes like hibiscus tea,
and the tea did significantly better. We’re still not
sure why it works, but hibiscus does appear to
boost nitric oxide production, which could help our arteries
relax and dilate better. Regardless, an updated review acknowledged
that the daily consumption of hibiscus tea may indeed significantly lower blood
pressures in people with hypertension, but by how much? How does this drop in blood pressure
compare to other interventions? Well, the premier clinical trial when
it comes to comprehensive lifestyle modification for blood pressure control is
the Premier Clinical Trial. Realizing that 9 out of 10 Americans
are going to develop hypertension, they randomized 800 men and women with
high blood pressure into one of three groups. One was the control group,
the so-called advice only group, where patients were just told
to lose weight, cut down on salt, increase exercise and eat healthier…
here’s a brochure.
In the two behavioral intervention
groups they got serious. 18 face-to-face sessions,
groups meetings, food diaries, monitored physical activity,
calorie and sodium intake. Now, one intervention group
just concentrated on exercise and the other one included
exercise and diet. They pushed the DASH diet,
high in fruits, and vegetables, and low in full-fat
dairy products and meat. And in six months achieved a 4.3 point
drop in systolic blood pressure, compared to the control, slightly better than
the lifestyle intervention without the diet.
Now, a few points might
not sound like a lot— that’s like someone going from a blood pressure
of 150 over 90 to a blood pressure of 146 over 90— but on a population scale a 5 point
drop in the total number could result in a 14% fewer stroke deaths,
9% fewer fatal heart attacks, and 7% fewer deaths every year overall. But a cup of hibiscus tea with each meal didn’t
just lower blood pressure by 3, 4 or 5 points but by 7 points, 129 down to 122. And in fact tested head-to-head against a
leading blood-pressure drug, called Captopril, two cups of strong
hibiscus tea every morning, using a total of 5 tea bags
for those 2 cups, was as effective in
lowering blood pressure as a starting dose of 25 mg of
Captopril taken twice a day.
So as good as drugs,
without the drug side-effects, and better than
diet and exercise? Well, the lifestyle interventions
were pretty whimpy. As public health experts noted,
the Premier study was only asking for 30 minutes
of exercise a day, whereas the World Health Organization
is more like an hour a day minimum. And diet-wise, the lower
the animal fat intake, and the more plant sources of protein
the Premier participants were eating, the better the diet
appeared to work, which may explain why vegetarian diets
appear to work even better, and the more plant-based the lower
the prevalence of hypertension. On the DASH diet, they were
told to cut down on meat, but were still eating
meat every day, so would qualify as the non-vegetarians
here in the Adventist 2 study, which looked at
89,000 Californians and found that those who instead only
ate meat on more like a weekly basis had 23% lower rates
of high blood pressure. Cut out all meat except fish
and the rate is 38% lower. Cut out all meat period—the vegetarians
have less than half the rate and the vegans—cutting out
all animal protein and fat— appeared to have thrown three quarters of their
risk of this major killer out the window.
One sees the same kind of step-wise
drop in diabetes rates as one’s diet gets more and more plant-based
and a drop in excess body weight such that only those eating completely
plant-based diets fell into the ideal weight category. But could that be why those eating
plant-based have such great blood pressure? Maybe it’s just because they’re
so skinny on average. I’ve shown previously how those
eating plant based diets have just a fraction of the diabetes
risk even at the same weight, even after controlling for BMI. But what about hypertension? The average American has
what’s called prehypertension, which means the top number of your blood
pressure is between 120 and 139.
Not yet hypertension,
which starts at 140, but it means we may
be well on our way. Compare that to the blood pressure of those
eating whole food plant-based diets. Not 3 points lower, 4 points lower, or even
7 points lower, but 28 points lower. Now, but the group here eating the
standard American diet was, on average, overweight with a BMI over 26,
still better than most Americans, but while the vegans were a trim 21
over here—that's 36 pounds lighter. So maybe the only reason those eating meat,
eggs, dairy, and processed junk had such higher blood pressure
was because they were overweight, maybe the diet per se
had nothing to do with it.
To solve that riddle we
would have to find a group still eating the standard American diet
but as slim as a vegan. To find a group that fit and trim, they
had to use long-distance endurance athletes, who ate the same
crappy American diet — but ran an average of 48 miles
a week for 21 years. They ran almost two marathons
a week for 20 years. So, if you do that, you know, anyone can be
slim as a vegan—no matter what they eat. So where did they
fall on this graph? Both the vegans and the conventional
diet group were sedentary— less than an hour
of exercise a week.
The endurance runners were here. So it appears if you run about
a thousand miles every year you can start to rival
some couch potato vegans. Doesn’t mean you can’t do both,
but it may be easier to just eat plants. Over the counter antacids are
probably the most important source for human aluminum exposure
in terms of dose. Maalox, for example, taken as directed,
can exceed the daily safety limit more than 100-fold, and nowhere on the
label does it say not take with acidic beverages
such as fruit juice. Washing an antacid down with
orange juice, for example, can increase aluminum
absorption 8-fold, and citric acid
was worse— the acid found naturally
concentrated in lemon and limes. Just as sour fruits can enhance
the absorption of iron, which is a good thing,
through the same mechanism they may enhance the
absorption of aluminum, raising the question what happens
when one adds lemon juice to tea? Previously, I concluded that the
amount of aluminum in tea is not a problem for most people
because it’s not very absorbable, but what if you
add lemon? No difference between
tea with lemon, tea without lemon,
or no tea at all in terms of the amount of
aluminum in the bloodstream, suggesting that tea drinking does
not significantly contribute to aluminum actually getting inside
the body-lemon juice or not.
Now, they’re talking about black tea,
green tea, white tea, oolong tea. What about the red zinger
herbal tea, hibiscus? The reason it’s called sour tea is because it
has natural acids in it like citric acid— might that boost the absorption
of any of its aluminum? Well, a greater percentage of aluminum gets
from the hibiscus into the tea water, but there’s less
aluminum overall. The question is does the aluminum then
get from the tea water into our body? We don’t have that data so to be on the
safe side we should assume the worst – that hibiscus tea aluminum, unlike
green and black tea aluminum, is completely absorbable. In that case, based on this data and the
World Health Organization weekly safety limit we may not want to drink more than
like 15 cups of hibiscus tea a day That’s based on someone
who’s about 150 pounds. So if you have a 75 pound
10-year-old, a half gallon of tea a day may
be theoretically too much. And more extensive testing
more recently suggests levels may be as high
as twice as much, so no more than about two quarts
a day for adults, or a quart a day for kids
every day or pregnant women.
And hibiscus tea should be completely
avoided by infants under 6 months— who should only be getting
breast milk anyway— as well as kids with kidney failure,
who can’t efficiently excrete it. The study also raised concern
about the impressive manganese level
in hibiscus tea. Manganese is an essential
trace mineral, a vital component of some of our
most important antioxidant enzymes, but we probably only need
2 to 5 milligrams a day, and 4 cups of hibiscus tea can have
as much as 17, averaging about 10.
Is that a problem? Well, women given 15 a day
for 4 months, if anything, only saw an improvement in their
anti-inflammatory, anti-oxidant enzyme activity. This study using 20 a day similarly
showed no adverse short-term effects, and importantly showed that the retention
of dietary manganese is regulated. Our body’s not stupid;
if we take too much in, our body decreases the absorption,
and increases the excretion. So, even though tea drinkers may
drink 10 times more manganese, you get 10 times more a day,
10 or 20 milligrams a day, the levels in their blood
is essentially identical. So, there is little evidence that
dietary manganese poses a risk. That was regular tea, though, we don’t
know about the absorption from hibiscus, so to err on the side of
caution we should probably not routinely exceed the reference
dose of 10 mg per day, so that’s only about a
quart a day for adults, a half quart for
a 75 pound child.
So, that’s actually changed
my family's consumption. Given the benefits of the stuff, I was using
it as a substitute for drinking water, so like 2 liters a day, and I was
blending the hibiscus petals in, not throwing them away, effectively
doubling aluminum content, and increasing manganese
concentrations by about 30%. So, given this data I’ve cut back to no more than
about a quart of filtered hibiscus tea a day..