Archive for category Tea'

The Effects of Tea on the Cardiovascular System

Cardiovascular diseases, together with cancers, are the main killing diseases of humans in the world. Of the cardiovascular diseases, atherosclerosis is one of the most prevalent. Atherosclerosis is primarily caused by hypercholesterolemia in which excess cholesterol accumulates in the blood vessels and oxidation of low-density cholesterol (LDL) leads to foci of endothelial abnormalities associated with the process of atherosclerosis (). It deteriorates further with the oxidation of lipids in the blood. Therefore, in order to maintain the cardiovascular system in good condition, it is very important to prevent not only an excessive increase of cholesterols in the blood, but also the oxidation of lipids in the blood. Hypertension is another major factor that can affect the health of the cardiovascular system. In this article, the antioxidative, hypolipidemic, hypotensive and the obesity-depressing activity of tea will be discussed. Antioxidative Activity of Tea Blood-Pressure Lowering Activity of Tea Blood Lipid and Cholesterol Lowering Effect Excessive lipids in blood is a common disorder of middle aged or old aged men and women. High serum-lipid includes high cholesterol and triglyceride content in blood. The cholesterol Read more […]

Antioxidative Activity of Tea

The role of free radical and active oxygen in the pathogenesis of certain human diseases, including aging, cardiovascular disease and cancer is becoming increasingly recognized. Lipid peroxidation has been regarded as one of the mechanisms of senescence of humans and the cause of atherosclerosis. Because of their very high chemical reactivity, free radicals show very short lifetimes in biological systems. However, the excessive amounts of free radicals are able to produce metabolic disturbances and to damage membrane structures in a variety of ways. Therefore, much attention has been focused on the use of antioxidants, especially natural antioxidants, to inhibit lipid peroxidation or to protect the damage of free radicals. Many investigations indicated that intake of certain amounts of fruits and vegetables that contain a large quantity of vitamin C and vitamin E showed antioxidative activity. Tea is not only rich in vitamin C and E, but also contains an important group of polyphenols, i.e., catechins, which display obvious antioxidative activity. The polyphenols are able to act as antioxidants by virture of the hydrogen-donating capacity of their phenol groups, as well as their metal-chelating potential (). As early Read more […]

Blood-Pressure Lowering Activity of Tea

Hypertension is a common disorder in humans. Te a drinking can lower blood pressure. There are many Chinese traditional prescriptions, with tea as a major constituent, used in the treatment of hypertension and coronary disease in Chinese traditional medicine. A survey on the relationship between hypertension and tea drinking in 964 adults was carried out by Zhejiang Medical University of China during the 1970s. Results showed that the average rate of hypertension was 6.2% in the group who drank tea as habit, and 10.5% in the group who did not. Clinical experiments showed that hot water extract of green tea possessed a degree of blood pressure lowering effect. An experiment in vivo carried out on rats fed with diet supplemented with 0.5% crude catechins showed that the blood pressure in treated rats was 10–20 mm Hg lower than that in the control group (). A clinical experiment using green tea on high blood pressure patients was conducted at the Anhui Medical Research Institute of China. Results showed that a 10 g tea intake daily treatment over half a year, decreased the blood pressure by 20–30% (). A study was conducted to determine whether the effect in vitro is reflected in the lowering of blood pressure of Read more […]

Obesity-Depression and Prevention of Cardiovascuear Disorders

Excessive lipid induces obesity. This is a physiologically abnormal phenomenon in modern society. Obesity is closely related to excessive serum lipid. Experiments show that tea drinking plays an obesity-depressing role via an increase of fundamental metabolic rate and the degradation of fat. Investigations carried out by French, Japanese and Chinese scientists have also shown that Pu-Er tea and Oolong tea possess a significant obesity depressing effect (). Researches using different kinds of tea revealed that the serum lipid depressing and obesity depressing effects of compressed tea was greater than that of green tea and black tea (). High levels of blood cholesterol induce the deposit of lipid on the vessel wall and cause the constriction of coronary arteries, atherosclerosis and thrombus formation. It is related to the fact that tea drinking decreases the serum lipid and cholesterol level. In the past, atherosclerosis was thought to result from a level of serum cholesterol above 200dl and a relatively low level of high-density cholesterol and high level of LDL. Current views are that it is induced by the oxidation of low-density cholesterol cholesterol that leads to foci of endothelial abnormalities associated Read more […]

Tea Extracts

Tea is a drink made from the dried leaves of Camellia sinensis; it is said to be the second most popular drink in the world after water. All tea starts as green but if the rolled and cut leaves are allowed to stand and ferment for 1-3 days before drying it becomes black. In green tea the enzyme that causes the blackening is inactivated by heat treatment which prevents blackening. Oolong tea is fermented for a shorter period and its colour and taste are between green and black tea. Tea leaves contain high quantities of polyphenols, which make up 20-30% of their dry weight. When tea leaves are rolled and crushed during processing, the enzyme polyphenol oxidase converts catechins (categorised earlier as flavonols) to polymeric forms, which give the fermented oolong and black teas their characteristic colours. Black tea is the form usually consumed in the UK although green tea is available and extracts of green tea in tablet form are marketed. Tea contains some essential nutrients but these probably provide only a tiny fraction of the adult requirement for these nutrients. Tea also contains the alkaloid caffeine and smaller amounts of theobromine which are responsible for the stimulating effect of the beverage. The components Read more […]

Herb-Drug Interactions: Tea

Camellia sinensis (L.) Kuntze (Theaceae) Synonym(s) and related species Camellia thea Link, Thea sinensis L. Note that Green tea (predominantly produced in China and Japan) is produced from steam-treated tea leaves. Black tea or Red tea (predominantly produced in India, Sri Lanka and Kenya) is processed by fermentation and heating, whereas Oolong tea is partially fermented. Pharmacopoeias Powdered Decaffeinated Green Tea Extract (The United States Ph 32). Constituents Tea contains caffeine (around 1 to 5%), with minor amounts of other xanthines such as theophylline and theobromine. Tea also contains flavonoids, the content of which varies between green (unfermented) and black (fermented) tea. Green tea appears to contain greater quantities of the flavonol-type flavonoids than black tea. Black tea also contains theaflavins, which are produced during the fermentation process. Other flavonols present include quercetin and kaempferol. Oolong tea contains some unique flavones known as oolonghomobisflavins. Tea also contains up to 24% tannins. Use and indications The leaf buds and very young leaves of tea are used as a stimulant and diuretic, actions that can be attributed to the caffeine content. They are Read more […]