In a new study, researchers found that compounds in both green and black tea relax blood vessels by activating ion channel proteins in the blood vessel wall.
The discovery helps explain the antihypertensive properties of tea and could lead to the design of new blood pressure-lowering medications.
The research was conducted by a team at the University of California, Irvine.
As many as one-third of the world’s adult population have high blood pressure, and this condition is considered to be the number one modifiable risk factor for global heart disease and premature mortality.
New approaches to treating hypertension have enormous potential to improve global public health.
The three commonly consumed caffeinated teas (green, oolong, and black) are all produced from the leaves of the evergreen species Camellia sinensis.
Black tea is commonly mixed with milk before it is consumed in countries including the United Kingdom and the United States.
In the study, the team found that two catechin-type flavonoid compounds (epicatechin gallate and epigallocatechin-3-gallate) found in tea, each activate a specific type of ion channel protein named KCNQ5.
As KCNQ5 is found in the smooth muscle that lines blood vessels, its activation by tea catechins was also predicted to relax blood vessels.
Prior studies demonstrated that drinking green or black tea can reduce blood pressure by a small but consistent amount, and catechins were previously found to contribute to this.
The researchers in the current study found that when black tea was directly applied to cells containing the KCNQ5 channel, the addition of milk prevented the beneficial KCNQ5-activating effects of tea.
The team also found, using mass spectrometry, that warming green tea to 35 degrees Celsius alters its chemical composition in a way that renders it more effective at activating KCNQ5.
They say regardless of whether the tea is consumed iced or hot, this temperature is achieved after the tea is drunk, as human body temperature is about 37 degrees Celsius.
One author of the study is Geoffrey Abbott, Ph.D.
The study is published in Cellular Physiology and Biochemistry.
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