Article

Health benefits of green tea

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Abstract

Tea is considered to be the highly consuming beverage in the world besides water. A sip of tea brings an instant energy and a feel of calm and relaxation to a hectic day. It is available in different forms out of which black, oolong and green tea are most popular. Over last few decades different researches and studies have been conducted to find out the effects of Green tea on human body and its intriguing benefits have made the researchers spell-bound. Green tea's popularity has been skyrocketed in recent years and it is found out to be one of the healthiest drinks. It appears to be highly preferential for various conditions from weight loss to liver disorders, cardiovascular diseases, type-2 diabetes mellitus and cancer. The purpose of this opinion is to highlight few purported positive effects that green tea exerts on human body.

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... Increasing consumer demand for healthy foods has stimulated the development of food products enhanced with bioactives, such as polyphenols, originating from natural sources. Green tea antioxidants have been well-recognised for a wide range of health benefits including protection against cancer (Balsaraf and Chole, 2015;Nasir and Abbas, 2014; Abbreviations: ANOVA, analysis of variance; AUC, area under the curve; AAPH, 22 -azobis-2-methyl-propanimidamide, dihydrochloride; EGCG, epigallocatechin gallate; FRAP, ferric reducing antioxidant power; HPLC, high performance liquid chromatography; ORAC, oxygen radical absorbance capacity; R c , retention coefficient; TE, Trolox equivalents; SGF, simulated gastric fluid; SIF, simulated intestinal fluid; TAA, total antioxidant activity; TPC, total phenolic content. inhibit redox-sensitive transcription factors, and minimise the effect of pro-oxidant enzymes (Frei and Higdon, 2003). ...
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Tea is grown in about 30 countries but is consumed worldwide, although at greatly varying levels. It is the most widely consumed beverage aside from water with a per capita worldwide consumption of approximately 0.12 liter per year. Tea is manufactured in three basic forms. Green tea is prepared in such a way as to preclude the oxidation of green leaf polyphenols. During black tea production oxidation is promoted so that most of these substances are oxidized. Oolong tea is a partially oxidized product. Of the approximately 2.5 million metric tons of dried tea manufactured, only 20% is green tea and less than 2% is oolong tea. Green tea is consumed primarily in China, Japan, and a few countries in North Africa and the Middle East. Fresh tea leaf is unusually rich in the flavanol group of polyphenols known as catechins which may constitute up to 30% of the dry leaf weight. Other polyphenols include flavanols and their glycosides, and depsides such as chlorogenic acid, coumarylquinic acid, and one unique to tea, theogallin (3-galloylquinic acid). Caffeine is present at an average level of 3% along with very small amounts of the other common methylxanthines, theobromine and theophylline. The amino acid theanine (5-N-ethylglutamine) is also unique to tea. Tea accumulates aluminum and manganese. In addition to the normal complement of plant cell enzymes, tea leaf contains an active polyphenol oxidase which catalyzes the aerobic oxidation of the catechins when the leaf cell structure is disrupted during black tea manufacture. The various quinones produced by the enzymatic oxidations undergo condensation reactions which result in a series of compounds, including bisflavanols, theaflavins, epitheaflavic acids, and thearubigens, which impart the characteristic taste and color properties of black tea. Most of these compounds readily form complexes with caffeine. There is no tannic acid in tea. Thearubigens constitute the largest mass of the extractable matter in black tea but their composition is not well known. Proanthocyanidins make up part of the complex. Tea peroxidase may be involved in their generation. The catechin quinones also initiate the formation of many of the hundreds of volatile compounds found in the black tea aroma fraction. Green tea composition is very similar to that of the fresh leaf except for a few enzymatically catalyzed changes which occur extremely rapidly following plucking. New volatile substances are produced during the drying stage. Oolong tea is intermediate in composition between green and black teas.