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Breakthrough study explains why tea reduces hypertension

In a breakthrough study from UC Irvine, researchers have uncovered an explanation for the antihypertensive effects of tea. The experts report that both green and black tea contain compounds that relax the blood vessels by activating ion channel proteins in the blood vessel wall. 

The discovery was made in the lab of Dr. Geoffrey Abbott, a professor in the Department of Physiology and Biophysics at the UCI School of Medicine. The findings may ultimately lead to the development of new medications for lowering blood pressure.

The researchers identified two flavonoid compounds that each activate a specific type of ion channel protein named KCNQ5. This protein allows potassium ions to diffuse out of cells to reduce cellular excitability. 

The team predicted that since KCNQ5 is found in the smooth muscle that lines blood vessels, its activation by tea catechins would also relax blood vessels.

“We found by using computer modeling and mutagenesis studies that specific catechins bind to the foot of the voltage sensor, which is the part of KCNQ5 that allows the channel to open in response to cellular excitation. This binding allows the channel to open much more easily and earlier in the cellular excitation process,” explained Dr. Abbott.

Previous studies have demonstrated that consumption of green or black tea can reduce blood pressure by a small but consistent amount, and catechins were found to contribute to this effect. 

The research has major implications for improving human health. Hypertension is a very common condition that is considered to be the number one modifiable risk factor for cardiovascular disease and premature mortality, 

Each day worldwide, more than two billion cups of tea are consumed, which is second only to water. The three most popular caffeinated teas – green, oolong, and black – are all produced from the leaves of the evergreen species Camellia sinensis.

In the UK and the United States, black tea is commonly mixed with milk. The researchers found that when black tea was directly applied to cells containing the KCNQ5 channel, the addition of milk prevented its activation. However, Dr. Abbott explained that milk is not likely to interfere with the antihypertensive effects of black tea.

“We don’t believe this means one needs to avoid milk when drinking tea to take advantage of the beneficial properties of tea. We are confident that the environment in the human stomach will separate the catechins from the proteins and other molecules in milk that would otherwise block catechins’ beneficial effects.”

“Regardless of whether tea is consumed iced or hot, this temperature is achieved after tea is drunk, as human body temperature is about 37 degrees Celsius,” explained Dr. Abbott. “Thus, simply by drinking tea we activate its beneficial, antihypertensive properties.”

The study is published in the journal Cellular Physiology and Biochemistry.

By Chrissy Sexton, Staff Writer

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