Three Cups of Black Tea a Day Can Help Lower Blood Pressure
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 pressure readings.
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 Controlled Trial
Arch Intern Med.2012; 172: 186-188.
National Heart Lung and Blood Institute, National Institutes of Health
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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