Effect of Acute and Chronic Tea Consumption on Platelet Aggregation in Patients With Coronary Artery Disease

Abstract

Abstract-Epidemiological studies suggest that tea consumption is associated with a decreased risk of cardiovascular events, but the mechanisms of benefit remain undefined. Platelet aggregation is a precipitating event in cardiovascular disease, and tea contains antioxidant flavonoids that are known to decrease platelet aggregation in vitro. To test the effect of tea consumption on platelet aggregation, we randomized 49 patients with coronary artery disease to either 450 mL of black tea or water consumed initially, followed by 900 mL of tea or water daily for 4 weeks in a crossover design. Ex vivo platelet aggregation in platelet-rich plasma was assessed in response to ADP and thrombin receptor-activating peptide at baseline and 2 hours and 4 weeks after beverage consumption. We observed dose-dependent platelet aggregation in response to each agonist, and neither relation was altered by acute or chronic tea consumption. Plasma flavonoids increased with acute and chronic tea consumption, indicating adequate absorption of tea flavonoids. In conclusion, these results demonstrate that acute and chronic black tea consumption does not affect ex vivo platelet aggregation in patients with coronary artery disease. These findings suggest that an effect of tea flavonoids on platelet aggregation is unlikely to be the explanation for the reduction in risk of cardiovascular events noted in epidemiological studies. Key Words: platelet aggregation Ⅲ tea Ⅲ flavonoids Ⅲ coronary artery disease R ecent epidemiological studies strongly suggest an inverse relationship between tea consumption and cardiovascular disease risk, 1-5 with 1 notable exception. 6 There is also convincing evidence that dietary intake of antioxidant flavonoids from tea and other sources (eg, red wine, onions, apples, and broccoli) is associated with reduced cardiovascular risk. [1][2][3][4][5][7][8][9] The benefit of high flavonoid intake may be greater for individuals with established coronary artery disease (CAD), 1,10 although favorable effects have also been demonstrated in people without evidence of atherosclerosis. 5,8,9 One proposed mechanism for the apparent benefit of tea and other sources of flavonoids is their favorable effect on platelet aggregation. [11][12][13][14][15][16] These polyphenols may inhibit platelet aggregation by a number of different mechanisms, including inhibition of lipoxygenase, cyclooxygenase, 13,17 cAMP phosphodiesterase, 12,18 and cGMP phosphodiesterase. 19 Other platelet-inhibitory effects of flavonoids include thromboxane receptor antagonism, 15 scavenging of reactive oxygen species such as superoxide anion, 20 decreasing phospholipase C activation by blunting hydrogen peroxide production, 21 and inhibition of lipid peroxidation. 14 Flavonoids also enhance nitric oxide (NO) production from the endothelium. 22 NO is a potent inhibitor of platelet adhesion, aggregation, [23][24][25] and thrombosis, 26 and impaired platelet production of NO has been associated with acute coronary syndromes. 27 A recent study demonstrated dose-...

Tea Consumption and Mortality After Acute Myocardial Infarction

“…28 Because alcohol consumption also has antithrombotic activity, 29 our finding that tea consumption seems most protective among alcohol abstainers supports this as a possible mechanism. Whether the observed association between tea consumption and postinfarction survival reflects these physiological effects of tea or confounding by other factors associated with tea intake can only be answered in a large-scale, long-term randomized trial, although such a trial is unlikely to be performed in the near future.…”

Acute EGCG Supplementation Reverses Endothelial Dysfunction in Patients with Coronary Artery Disease

“…[23,24] The nitroglycerin portion of the study was omitted if systolic blood pressure was less than 100 mmHg, if the subject had a history of migraine headaches, or if he or she reported a previous history of prior adverse reaction to nitroglycerin. Ultrasound images (Powervision 6000, Toshiba Medical, Inc., Tustin, CA) were digitized online using customized hardware (Cardiovascular Engineering, Inc., Holliston, MA).…”

Nutritional Management of Disturbances in Lipoprotein Concentrations

“…Although some studies have found no lipidlowering effects from green or black tea consumption, most showed hypolipidemic effects for tea [213][214][215][216][217][218]. The association between tea drinking and lipid profile concentrations was linear for up to 10 cups per day, beyond which the association disappeared [219].…”