Green tea contains high concentrations of substances that improve your health and lower your risk of chronic diseases and conditions, including atherosclerosis, high cholesterol, diabetes, cancer, liver disease and inflammatory bowel disease. Scientists at the University of Granada in Spain report that green tea has blood-pressure-lowering effects, according to research published in the "Journal of the American College of Nutrition" in April 2006. Consult your doctor about green tea and blood pressure.
Green Tea
Green tea is among the most popular beverages worldwide and is also available in supplements as a dry leaf in capsules and liquid extracts made from leaves and leaf buds. Green tea contains catechins, alkaloids, theanine and other nutrients and substances. Catechins, such as epigallocatechin gallate, are types of polyphenols with strong antioxidant properties greater than vitamin C. Alkaloids in green tea include caffeine, theophylline and theobromine, compounds that stimulate your nervous system. L-theanine is an amino acid that calms your nerves. One or more of these substances may affect blood pressure.
Blood Pressure
Blood pressure is a measurement of the force that is applied to the walls of your arteries as your heart pumps blood through your body and is determined by the amount of blood pumped and size and flexibility of your arteries. Your blood pressure consists of two measurements. Your systolic blood pressure is a measurement of the maximum pressure that occurs when your heart contracts, and diastolic pressure is a measurement of the minimum pressure that occurs when your heart is at rest. High blood pressure, also called hypertension, is a risk factor for stroke, heart attack, heart failure and kidney disease.
Animal Studies
Green tea reduces your risk of high blood pressure and subsequent complications. Scientists at Kinjo Gakuin University in Nagoya, Japan, compared the effects of green tea, black tea and water in stroke-prone hypertensive rats and found that both green tea and black tea polyphenols reduce both systolic and diastolic blood pressure, according to research published in the "Journal of Nutrition" in January 2004. The scientists conclude that regular consumption of green tea provides protection against high blood pressure in humans.
Human Studies
Human studies suggest that green tea consumption is beneficial for blood pressure and reduces risk of stroke. Scientists at the University of Western Australia found that, compared to caffeine, green tea in humans increases blood pressure within 30 minutes of consumption, but blood pressure declines thereafter, according to research published in the "Journal of Hypertension" in April 1999. Daily consumption of 3 cups of green tea may prevent the onset of ischemic stroke, according to research by scientists at the University of California at Los Angeles and published in "Stroke” in May 2009.
References
- University of Maryland Medical Center; Green Tea; September 20, 2010
- "Journal of the American College of Nutrition"; Beneficial Effects of Green Tea--a Review; Carmen Cabrera, et al.; April 2006
- Medline Plus; Blood Pressure; June 3, 2011
- "Journal of Nutrition"; Black and Green Tea Polyphenols Attenuate Blood Pressure Increases in Stroke-Prone Spontaneously Hypertensive Rats; Hiroko Negishi, et al.; January 2004
- "Journal of Hypertension"; Effects on Blood Pressure of Drinking Green and Black Tea; J.M. Hodgson, et al.; April 1999
- "Stroke"; Green and Black Tea Consumption and Risk of Stroke: A Meta-Analysis; Lenore Arab, et al.; May 2009
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