Green Tea and Health benefits
The importance of research on tea and health has been well recognized worldwide since around 1990, and several international symposiums in succession have been held on this theme.
Tea is a refreshing, thirst-quenching beverage. Moreover, the benefits of tea drinking on human health have long been taught by generations of people who in their daily lives used tea as a home remedy for a variety of ailments and believed in the results. Yet, in scientific terms, the association of the benefits of tea drinking with tea polyphenols is rather new. Decades ago, components such as caffeine or vitamin C were considered the principal constituents in green tea that exert beneficial effects on human health.
Today the tea bush is known as Camellia sinensis (L.) O. Kuntze of which there are two varieties: var. sinensis and var. assamica. In 1690, E. Kaempfer, a German medical doctor cum botanist who came to Japan from Holland and observed the habit of tea drinking among the people, named the bush "thea." In 1753, the famed botanist C. Linne´ gave to it the name of Camellia sinensis changing his original naming of Thea sinensis. Since then the nomenclature of the tea bush has been confused between these two names. In 1958, a British botanist J. R. Sealy classified all plants in the genus Camellia and tea was given the name it has today.
The tea that today is commonly consumed in countries all over the world was once revered for its curative powers. Some of the earliest mentions of tea in Chinese literature refer to it as a remedy for a diverse range of complaints. Gradually though, tea became more and more commonly consumed and its role in society started to shift from that of a highly esteemed panacea to one of being simply a refreshing and habitual beverage.
The Chemical History Of Tea
While the history of tea drinking is ancient, investigation into the chemical components of tea is in comparison quite recent. Tea is composed of unique constituents among other plants. Caffeine is found only in a few other plants other than tea. Theanine, which is unique to tea, is a kind of amino acid constituting more than half the total amount of amino acids in tea. Major catechins in tea are also unique to tea. Vitamin C was found to be contained in tea after it was discovered in lemons. Tea aroma is an area that attracted the interest of scientists who had been seeking one single compound that represents tea, a search which has yet been in vain.
Antioxidative Action of Tea (Polyphenols - a walk through into research)
Possible applications for tea catechins in numerous fields continue to grow as more and more is discovered about their antioxidative action. Since oxidative reactions are regarded as being detrimental to the body, extensive research over recent years has been undertaken to seek out ways of combating these processes. Various different compounds found in all kinds of plants, vegetables, and fruits have been found to have antioxidative action. Among these are the polyphenols exclusive to tea, which have been proved to be even more effective than some well-known and commonly used antioxidants. Both in vitro and in vivo experiments have given positive results, broadening the possibilities for practical applications.
Antioxidative Action In Lard
Oxidative reactions occur not only within our bodies but also in our food, causing deterioration of freshness and quality before consumption. Tackling this problem is an extremely important issue for the food industry. Various antioxidants have been used in the past, including both those derived from natural sources and those synthetically produced. Catechins derived from tea leaves are natural, safe for consumption, and have been proved to be very effective antioxidants.
Prevention of Cancer by Tea Polyphenols
There is a saying that prevention is better than cure. This way of thinking certainly seems to be increasingly prevalent with regards to research into cancer. Exploding expenses for cancer therapy in the national budget will force many people involved in cancer treatment and research to explore cancer prevention methods through diet rather than concentrating on hospital cures for cancer. Cancer originates from mutagenesis brought about by various physical, chemical, and biological causes in the DNA of the cell.
Tea polyphenols have a strong radical scavenging and reducing action. They scavenge radicals produced endogenously as oxygen radicals or by exposure to radiation or UV light, as well as those produced by cancer promoters, and render them harmless; while in the digestive tract they reduce nitrite, thus preventing production of nitroso-amine, which causes cancer. Tea polyphenols also show a tendency to form strong bonds.
with proteins, and it is known that at low concentrations they inactivate some enzymes and viruses. There is the possibility that tea polyphenols will inactivate some viruses that cause cancer. Thus, tea polyphenols have the potential to work in a preventative way against many of the causes of cancer.
Inhibitors of mutagenesis have been classified as "desmutagens" and "bioantimutagens" by Kada (1). Desmutagens are substances that directly act on mutagens chemically, enzymatically, or physically to inhibit mutagenesis, and bioantimutagens work on cells that have undergone mutagenesis to inhibit their mutagenic expression. Antimutagenic andanticarcinogenic activity of tea polyphenols has searched for bioantimutagens in natural elements as well as in foodstuffs and found bioantimutagenic activity in tea extract solution. The active
component was found to be epigallocatechin gallate (EGCg)(catechin)
In recent years, molecular level studies are under way on the mutagenicity of DNA in relation to oxygen radicals. Oxy radicals cause hydroxylation or methylation in DNA and that tea catechins inhibit these sequential events. Detailed studies are awaited.
When a promoter acts repeatedly on a living organism whose DNA has been mutated by an initiator, cancer is induced. If repeated administrations of a substance before and after administration of the promoter inhibit cancer in the body then that substance can be said to have an antipromotion action. Components of tea, particularly EGCg, have been proven to have an antipromotion action. Fujiki et al. applied an initiator (DMBA) to the backs of mice and then twice a week for 25 weeks a promoter, teleocidin, was applied. In the test group 5 mg EGCg was applied 15 minutes before each application of teleocidin. Results showed that as compared with the control, the number of tumors in the test group was markedly less. They also confirmed the effectiveness of EGCg using another promoter, okadaic acid, which has a different mechanism than teleocidin. It was hypothesized that EGCg has a "sealing effect", that is, EGCg seals the promoter receptors on the cells and prevents the binding of the promoter to the cells.