Tea is the most consumed drink in the world after water. Green tea is a product made from the “Camellia sine sis” plant. It can be prepared as a beverage, which can have some health effects. Green tea is used to improve mental alertness and thinking. It is a ‘non-fermented’ tea, and contains more catechins (antioxidants)and theanine. Theanine is an amino acid naturally found in tea leaves. It is also used for weight loss and to treat stomach disorders, headaches, osteoporosis, and solid tumour cancers. In addition, its content of certain minerals and vitamins increases the antioxidant potential of this type of tea. Since ancient times, green tea has been considered by the traditional Indian and Chinese medicine as a healthful beverage. The most of the people use green tea to prevent various cancers, including breast cancer, prostate cancer, lung cancer. Instead of drinking green tea, some people apply green tea bags to their skin to soothe sunburn and prevent skin cancer due to sun exposure. Increasing interest in its health benefits has led to the inclusion of green tea in the group of beverages with functional properties.
Key words: Osteoporosis, catechins, Theanine
Tea has been cultivated for centuries, beginning in India and China. Today, tea is the most widely consumed beverage in the world after water. Hundreds of millions of people drink tea, and studies suggest that green tea (Camellia sinesis) in particular has many health benefits. There are three main varieties of tea: – green, black, and oolong. The difference is in how the teas are processed. Green tea is made from unfermented leaves and reportedly contains the highest concentration of powerful antioxidants called polyphenols. The cardinal antioxidative ingredient in the green tea extract is green tea catechins, which comprise four major epicatechin derivatives; namely, epicatechin, epigallocatechin, epicatechin gallate, epigallocatechin gallate. Caffeine may be excluded in green tea extracts in order to avoid side-effects; caffeine-free green tea extract supplements are now available. Green tea extract is 20 times more antioxidant-active than Vitamin C. Antioxidants are substances that fight free radicals damaging compounds in the body that change cells, damage DNA, and even cause cell death. Antioxidants such as polyphenols in green tea can neutralize free radicals and may reduce or even help prevent some of the damage they cause. In traditional Chinese and Indian medicine, practitioners used green tea as a stimulant, a diuretic (to help rid the body of excess fluid), an astringent (to control bleeding and help heal wounds), and to improve heart health. Other traditional uses of green tea include treating gas, regulating body temperature and blood sugar, promoting digestion, and improving mental processes
Benefits of green tea
Studies show that green tea catechins provide some protection against degenerative diseases. It indicated that green tea has an antiproliferative activity on hepatoma cells and a hypolipidemic activity in hepatoma-treated rats, as well as the prevention of hepatoxicity and as a preventive agent against mammary cancer post-initiation Moreover, green tea, and its isolated constituents were also found to be effective in preventing oxidative stress and neurological problems. Green tea consumption has also been linked to the prevention of many types of cancer, including lung, colon, oesophagus, mouth, stomach, small intestine, kidney, pancreas, and mammary glands. Several epidemiological studies and clinical trials showed that green tea (and black and Oolong teas to a lesser extent) may reduce the risk of many chronic diseases In particular green tea may lower blood pressure and thus reduce the risk of stroke and coronary heart disease.
Adverse effects of green tea
Although green tea has several beneficial effects on health, the effects of green tea and its constituents may be beneficial up to a certain dose yet higher doses may cause some unknown adverse effects. Moreover, the effects of green tea catechins may not be similar in all individuals. EGCG of green tea extract is cytotoxic, and higher consumption of green tea can exert acute cytotoxicity in liver cells, a major metabolic organ in the body and also causes cause oxidative DNA damage of hamster pancreas and liver. At a high dose (5% of diet for 13 wk), green tea extract induced a thyroid enlargement (goitre). Green tea should not be taken by patients suffering from heart conditions or major cardiovascular problems. Pregnant and breast-feeding women should drink no more than one or two cups per day, because caffeine can cause an increase in heart. Likewise, green tea catechins may have an affinity for iron, and green tea infusions can cause a significant decrease of the iron bioavailability from the diet
Laboratory studies showed the health effects of green tea. As the human clinical evidence is still imited, future research needs to define the actual magnitude of health benefits, establishes the safe range of tea consumption associated with these benefits, and elucidates the mechanisms of action
I sincerely thank to Sk. Raziya begum madame, for giving his valuable guidance.
Essential properties of green tea