How Green Tea Affects Blood Pressure
By Solha Park, PharmD & Moa Park, PharmD
Among the major risk factors of developing cardiovascular diseases such as heart attack, heart failure and stroke, high blood pressure is the most closely and consistently related to the development of cardiovascular disease requiring immediate treatment with medications and lifestyle modifications . While there are many ways to control high blood pressure, regular consumption of green tea has been shown to have a positive relationship with lowering blood pressure when combined with healthy diet and regular exercise [2-5].
High blood pressure is a chronic medical condition that can lead to many serious health problems including cardiovascular diseases and kidney disease. Persistent high blood pressure may damage other parts of body such as blood vessels and eyes. While it does not have any symptoms, these long-term compli- cations usually take several years to develop. Fortunately, high blood pressure can be detected easily through a regular medical checkup and can be controlled with lifestyle modification and medications .
Blood pressure is measured as two different pressure types: systolic and diastolic blood pressure. Systolic blood pressure refers to the measurement of blood pressure when the heart pumps out the blood, and diastolic blood pressure refers to the pressure in between two heartbeats. The systolic numbers are often written above or before the diastolic numbers and are higher. The following table shows different stages from normal blood pressure to stage 1 and 2. The level of the patient’s high blood pressure determines what kind of treatment one may need .
Important risk factors of high blood pressure are age, gender, family history, and lifestyle including lack of physical activity, obesity, diets high in sodium (from salt), and some medications. About one out of three adults in the United States develop high blood pressure . Older people are more likely to develop high blood pressure, and men tend to develop high blood pressure earlier than women at the age of 55 and older. High blood pressure can also be hereditary .
How is blood pressure regulated? Blood pressure is regularly maintained by various chemicals in our bodies that send signals to several layers in blood vessels, such as elastic fibers, smooth muscles and connective tissues. Angiotensin, a powerful constrictor of the blood vessels, is an endogenous hormone (a hormone made in human body). Upon activation, it signals stress hormones to be released, constricting the blood vessels by tightening the smooth muscles surrounding the vessels, and causing the kidneys to reduce fluid loss . As a result, blood volume increases and blood vessels become narrower raising the blood pressure. On the other hand, nitric oxide, a dilator, is a gaseous chemical in our bodies involved in lowering blood pressure. When it is released into blood vessels, it relaxes the smooth muscles and dilates the vessels, which keep blood vessels open as shown in the above figure [7,8]. By doing so, nitric oxide decreases the pressure in blood vessels and allows for increased blood flow.
According to recent animal studies on green tea and high blood pressure, catechins in green tea have been shown to affect the activities of angiotensin and nitric oxide. EGCG in green tea has been shown to interfere with the activation process of angiotensin and consequently cause a decrease in blood pressure. EGCG has also been shown to promote biological production of nitric oxide [9-11].
Moreover, drinking green tea has been associated with lowering blood pressure in many population studies. Catechins, the major chemicals found in green tea, have been shown to be an antioxidant. The antioxidant effect of catechins in green tea can reduce damages to the blood vessels caused by free radicals and help preserve normal blood vessel function over time .
As the beneficial health effects of green tea are constantly being studied, it would be advisable to encourage the habitual consumption of green tea, especially for those at risk of developing high blood pressure or already suffering from the condition. Although a single food item should not be expected to have a significant impact on one’s health, regular consumption of green tea combined with an improved lifestyle, such as regular physical exercise and healthy diet, may have a great impact on maintaining normal blood circulation and better health.
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