Green Tea And High Blood Pressure: Latest Research

Green Tea And High Blood Pressure
Latest Research

Green tea and high blood pressure: Latest research shows
65% lower risk of high blood pressure for middle-aged people*.

*1500 middle-aged normal people in Taiwan were checked for the development of high blood pressure during an 8-year study.

Researchers compared three groups:

those who drank over 20 ounces of green or oolong tea daily for more than a year.
those who drank between 4 ounces (120 ml.) and 20 ounces (600 ml.) of green or oolong tea daily
those who drank no tea or less than 4 ounces of green or oolong tea daily (120 ml.)

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People who drank more than 20 ounces of green or oolong tea daily for more than a year showed the greatest protection-65% lower risk of high blood pressure during the 8 year study.

People who drank 4 ounces to 20 ounces of green or oolong tea daily for more than a year showed 46% lower risk of high blood pressure.

People who did not drink tea or drank less than 4 ounces daily had no protection from high blood pressure.

This protection from the development of high blood pressure by drinking tea did not show up statistically until after one year of daily use.
(Yang, 2004)

ACE, one cause of high blood pressure, is inhibited

Two studies show that green tea catechins, especially EGCG, inhibits ACE, an enzyme that leads to uncontrolled strong vascular constriction, which forces the blood pressure to rise. (Actis-Goretta, 2006, Li, 2006)

Animal studies showed:

EGCG from green tea was compared with enalapril in genetically hypertensive rats. Both green tea and enalapril significantly lowered blood pressure and improved insulin metabolism. EGCG also significantly reduced damage from stroke and improved heart function. (Potenza, 2007)
Green tea blocked salt uptake in the intestine during a high salt diet leading to lowered blood pressure. Also theanine, a protein from green tea, lowered blood pressure in genetically hypertensive rats but not in normal ones. (Kreydiyyeh 1994)
Whole green tea prevented constriction of arteries that causes high blood pressure. EGCG, the strongest antioxidant in green tea, when used alone had no effect on arterial walls. (Lim 2003)
A three week study with genetically hypertensive rats used the human equivalent of 1 quart of tea daily and attributed prevention of high blood pressure to antioxidants in the tea. (Negishi 2004)
A 12 week study with rats fed a high sugar diet found that green tea gave significant protection from the development of both high blood pressure and insulin resistance. (Wu, 2004)
High doses of theanine from green tea lowered blood pressure in genetically hypertensive rats but maintained normal blood pressure in normal rats. (Yokigoshi, 1995)
But, one long-term animal study did not show that daily green tea lowered blood pressure in genetically hypertensive animals, but did show strong prevention of strokes and significantly increased their life span. (Uchida, 1995)

Short-term human studies were inconclusive:

Researchers reported on an 87 day human weight loss study, but could only attribute lowered blood pressure to modest weight loss, not to green tea. (Diepvens, 2006)
A two month study of diabetics showed no significant differences between the green tea and water groups. (Fukino, 2005)
A 7 day study of humans found an insignificant increase in blood pressure after drinking green or black tea that disappeared when they were standing up. (Hodgson, 1999)

References for Green Tea and High Blood Pressure: Latest Research:

Actis-Goretta L, et al: Inhibition of angiotensin converting enzyme activity by flavanol-rich foods. J Agric Food Chem. Jan 2006; 54: 229-34.

Diepvens K, et al: Metabolic effects of green tea and of phases of weight loss. Physiol Behav. Jan 2006; 87:185-91.

Fukino Y, et al: Randomized controlled trial for an effect of green tea consumption on insulin resistance and inflammation markers. J Nutr Sci Vitaminol. Oct 2005; 51: 335-42.

Henry JP, and Stephens-Larson P.: Reduction of chronic psychosocial hypertension in mice by decaffeinated tea. Hypertension. May-June 1984; 6: 437-44.

Hodgson JM, et al: Effects on blood pressure of drinking green and black tea. J Hypertension. Apr 1999;17: 457-63.

Kreydiyyeh SI, et al: Tea Extract Inhibits Intestinal Absorption of Glucose and Sodium in Rats. Comp Biochem Physiol Pharm Tox Endocrin. July 1994; 108: 359-365

Li, HL, et al: Epigallocathechin-3 gallate inhibits cardiac hypertrophy through blocking reactive oxidative species-dependent and -independent signal pathways. Free Radic Biol Med. May 2006; 40: 1756-75

Lim DY, et al: Comparison of green tea extract and epigallocatechin gallate on blood pressure and contractile responses of vascular smooth muscle of rats. Arch Pharm Res. Mar 2003; 26: 214-23.

Negishi H, et al: Black and green tea polyphenols attenuate blood pressure increases in stroke-prone spontaneously hypertensive rats. J Nutr. Jan 2004; 134: 38-42.

Potenza, MA, et al: Epigallocatechin gallate, a green tea polyphenol, improves endothelial function and insulin sensitivity, reduces blood pressure, and protects against myocardial ischemia/referfusion injury in spontaneously hypertensive rats (SHR). Am J Physiol Endocrin Metab Jan 2007

Riemersma RA, et al: Tea flavonoids and cardiovascular health. QJM. May 2001; 94: 277-82.

Uchida S, et al: Effects of (-)-epigallocatechin-3-O-gallate (green tea tannin) on the life span of stroke-prone spontaneously hypertensive rats. Clin Exp Pharmacol Physiol Suppl. Dec 1995; 22: S302-3.

Weisburger JH: Worldwide prevention of cancer and other chronic diseases based on knowledge of mechanisms. Mutat Res. Jun 1998; 402: 331-7.

Wu LY, et al: Green tea supplementation ameliorates insulin resistance and increases glucose transporter IV content in a fructose-fed rat model. Eur J Nutr. Apr 2004; 43: 116-24.

Yang YC, et al: The protective effect of habitual tea consumption on hypertension. Arch Intern Med. July 2004; 164: 1534-40.

Yokogoshi H, et al: Reduction Effect of Theanine on Blood Pressure and Brain 5-hydroxyindoles in Spontaneously Hypertensive Rats. Biosci Biotech Biochem. Apr 1995: 59: 615-618.

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