Moderate Intake of Flavonoid-Rich Tea, Green or Black, Confers Cardiovascular Protection

Abstract

A variety of dietary supplements have been proposed for the management of hypertension and other cardiovascular diseases, but the evidence for their efficacy is meagre.¹ However, over the last few years, there is growing interest in the potential benefit of tea in cardiovascular protection.^2-4 Tea is the extract of Camellia sinensis, and one of the most widely enjoyed drinks.^2,3 The leaves of the plant are rich in flavonoids, containing several phytochemicals including phenols and catechins, to which potent antioxidant, free radical scavenging, appetite-modifying and hypolipidemic effects have been ascribed.^2-7 Long-term consumption of beverages containing catechins inhibits the formation of oxidized lipids and decreases body fat.^5-9 Over 70% of flavonoids in green tea are catechins. Epigallocatechin-3-gallate (EGCG) is the cardinal (65%) catechin in green tea. In-vitro studies have shown that the epigallocatechins in green tea have angiotensin converting enzyme inhibitor properties,¹⁰ and vasodilatory actions. ¹¹ Molecular and animal studies have demonstrated that green tea catechins enhance processes, thought to stimulate bile acid production, decrease cholesterol concentration in the hepatocytes, inhibit intestinal absorption of lipids and upregulate low-density lipoprotein (LDL) receptors in the liver, mechanisms all leading to favorable blood lipid profile.^2-4,12,13

Black tea also contains small amounts of catechins. However, due to the fermentation process of black tea, its primary antioxidant polyphenols are theaflavins and thearubigins, equally effective antioxidants to catechins. ^{14... (excerpt)}