Polyphenol in tea - health benefits
Polyphenols are a group of chemical substances found in plants. The name polyphenol comes from the fact that there is more than one phenol group per molecule.
Polyphenols in the Japanese diet
Coffee and green tea as a large source of antioxidant polyphenols in the Japanese population.
J Agric Food Chem. 2009. Nestle Research Center, Vers-chez-les-Blanc Lausanne, Switzerland.
Food and beverages rich in polyphenols with antioxidant activity are highlighted as a potential factor for risk reduction of lifestyle related diseases. This study was conducted to elucidate total polyphenol consumption from beverages in Japanese people. Total polyphenol contents in beverages were measured. A beverage consumption survey was conducted in the Tokyo and Osaka areas in 2004. Concentration in coffee, green tea, black tea, Oolong tea, barley tea, fruit juice, tomato/vegetable juice, and cocoa drinks were at 200, 115, 96, 39, 9, 34, 69, and 62 mg/100 mL, respectively. Total consumption of beverages in a Japanese population was 1.11 L/day, and polyphenol contents from beverages was 853 mg/day. Coffee and green tea shared 50% and 34% of total polyphenol consumption in beverages, respectively, and contribution of each of the other beverages was less than 10%. total polyphenol contents in 20 major vegetables and 5 fruits were 0-49 mg and 2-55 mg/100 g, respectively. Beverages, especially coffee, contributed to a large share of the consumption of polyphenols, as antioxidants, in the Japanese diet.
Polyphenol in food
Good sources of polyphenols include tea, coffee, berries, grapes, wine, olive oil, cacao or cocoa, walnuts, and many fruits and vegetables. High levels of polyphenols can generally be found in the fruit skins.
Polyphenol in green tea
The major polyphenol in green tea is EGCG.
Benefit for cardiovascular health
Nutritional improvement of the endothelial control of vascular tone by polyphenols: role of NO and EDHF.
Pflugers Arch. 2010. Schini-Kerth VB, Auger C, Kim JH, Etienne-Selloum N, Chataigneau T. UMR CNRS, Laboratoire de Biophotonique et Pharmacologie, Faculté de Pharmacie, Université de Strasbourg, Illkirch, France,
Numerous studies indicate that regular intake of polyphenol-rich beverages (red wine and tea) and foods (chocolate, fruit, and vegetables) is associated with a protective effect on the cardiovascular system in humans and animals. Beyond the well-known antioxidant properties of polyphenols, several other mechanisms have been shown to contribute to their beneficial cardiovascular effects. Indeed, both experimental and clinical studies indicate that polyphenols improve the ability of endothelial cells to control vascular tone. Experiments with isolated arteries have shown that polyphenols cause nitric oxide (NO)-mediated endothelium-dependent relaxations and increase the endothelial formation of NO. The polyphenol-induced NO formation is due to the redox-sensitive activation of the phosphatidylinositol3-kinase/Akt pathway leading to endothelial NO synthase (eNOS) activation subsequent to its phosphorylation on Ser 1177. Besides the phosphatidylinositol3-kinase/Akt pathway, polyphenols have also been shown to activate eNOS by increasing the intracellular free calcium concentration and by activating estrogen receptors in endothelial cells. In addition to causing a rapid and sustained activation of eNOS by phosphorylation, polyphenols can increase the expression level of eNOS in endothelial cells leading to an increased formation of NO. Moreover, the polyphenol-induced endothelium-dependent relaxation also involves endothelium-derived hyperpolarizing factor, besides NO, in several types of arteries. Altogether, polyphenols have the capacity to improve the endothelial control of vascular tone not only in several experimental models of cardiovascular diseases such as hypertension but also in healthy and diseased humans.