Three Cups of Black Tea a Day Can Help Lower Blood Pressure by Denise Reynolds RD
Over the past decade, there has been much research about the
health benefits of green tea, including its potential to fight
cancer and heart disease, prevent diabetes, and stave off dementia.
But don't discount the potential of other types of tea, including
black tea. Researchers with The University of Western Australia
have linked regular consumption of black tea with lowered blood
Research professor Jonathan Hodgson PhD of UWA's School of
Medicine and Pharmacology followed 95 Australian patients, between
the ages of 35 and 75, for six months. He divided participants into
one of two groups. The experimental group drank three cups of black
tea each day while the control group drank a placebo with the same
flavor and caffeine content.
At the end of the study, those drinking black tea had lower
24-hour systolic (the top number in a blood pressure reading) and
diastolic (the bottom number) readings of between 2 and 3 mmHg.
Systolic blood pressure is the pressure exerted on the blood
vessels when the heart beats to pump blood. A normal systolic blood
pressure is less than 120. Diastolic is the pressure exerted while
the heart is at rest. This number should be less than 80. A blood
pressure reading of 140/90 or above indicates hypertension, or high
blood pressure, but any level above normal 120/80 increases
cardiovascular disease risk.
Black tea is made from the aged leaves of the Camellia sinesis
plant. Green tea is actually made from the same plant, but from
fresh leaves. Antioxidants and other substances rich in tea leaves
may protect the heart and blood vessels. Previous studies have
linked the regular consumption of tea with decreasing the risk of
heart attacks and reducing the risk of atherosclerosis (hardening
of the arteries) in women.
Black tea may also be effective for increasing mental alertness,
reducing the risk of kidney stones, reducing the risk of
Parkinson's disease and decreasing the risk of ovarian cancer.
The primary polyphenols in black tea associated with health
benefits are called theaflavins. The average amount of theaflavin
in a cup of black tea is 12.18 mg. Theaflavin may affect blood
pressure because of its involvement with nitric oxide (NO)
production. People with atherosclerosis or hypertension often show
impaired NO pathways.
Black tea may also lower stress hormone levels, such as
cortisol, which increases blood pressure and heart rate.
"There is already mounting evidence that tea is good for your
heart health, but this is an important discovery because it
demonstrates a link between tea and a major risk factor for heart
disease," said Dr Hodgson. Of course more research is required to
better understand the benefits of black tea and its effects on
blood vessels, blood pressure, and cardiovascular processes.
Hodgson et al. Effects of Black Tea on Blood Pressure: A Randomized
Arch Intern Med.2012; 172: 186-188.
National Heart Lung and Blood Institute, National Institutes of
Medline Plus, US National Library of Medicine, National
Institutes of Health
U.S. Department of Agriculture, USDA Database for the Flavonoid
Content of Selected Foods, Release 2.1, January 2007
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