The medicinal properties associated with tea, as well as the low caffeine levels, are not supported by modern scientific studies. This is due to the fact that the tea plant grows in so many regions and can be processed in so many different ways, tests on one tea do not prove effects of all tea. Even individuals brewing technique will change the chemical compounds infused, and their rate of absorption. It is premature to make the call on relative antioxidant counts, because of the number of contradictory studies and the lack of a long term study with control groups.
During infusion, some chemical components, such as vitamin C, are destroyed, whereas others are more easily dissolved into the liquid. Many of the bioactive compounds in the tea leaves still do make it into the final drink, which contains large amounts of important nutrients. Roughly a cup of tea is composed of several hundred active substances.
While tea leaves contain the components found in every living organism and those characteristic of plant species, it is the presence of polyphenols and alkaloids that gives an infusion of tea leaves such astonishing properties. Each leaf is loaded with polyphenols, such as flavonoids and catechins, which function as powerful antioxidants. Polyphenols are a combination of several groups of phenols that make up a family of organic molecules present throughout the plant kingdom. In tea, these phenols are found in the catechins, of which tannins are the main component. Tannins have astringent properties that make living tissues contract, these polyphenols give tea its astringency, strength and thickness. These substance can reduce the formation of free radicals in the body, protecting cells and molecules from damage, by fighting the breakdown of cellular membranes caused by various stressors. They may also prevent the development of the metastases that lead to cancerous tumours.
However, that does not mean that tea doesn’t have solid health benefits. Many of these claimed benefits can be attributed to the low levels of theine present in tea. Theine and caffeine are the same alkaloid, and has been recognised as being identical in 1838, the caffeine in tea is nonetheless distinguishable from the caffeine found in coffee because it forms different bonds with other substances, which in turn changes how it affects the body. When tea leaves are infused, the caffeine combines with tannins, which attenuate and stabilise the caffeines affects on the body. Tannins prevent caffeine being released to rapidly, so it can be absorbed over along period of time, the effect therefore is more regular as well as lasting longer. In tea, caffeine stimulates the central nervous system and the cardiovascular system by enlarging the diameter of the vessels in the cerebral cortex. On the other hand, when ingested with coffee, caffeine has a direct affect on blood circulation through the coronary system, stimulating an acceleration of the heart rate. In other words tea is more of a stimulant than an excitant. It sharpens the mind, increases concentration, eliminates fatigue and enhances intellectual acuity. For many the effects of caffeine in tea are much milder and more harmonious with their metabolism than the caffeine of coffee.
The analysis of the caffeine content of various types of tea, leads scientists to believe that there is no real consistency. In every tea family, some teas contain very little caffeine while others contain a lot.
In addition, like all drinks, tea provides liquid, which helps keep you hydrated, and offers a chance to stop in the middle of the day and enjoy a treat. The effect of even 15 minutes of daily meditation has been documented to relieve stress. Stress and dehydration are major contributors to physical ailment. Decades of lower stress levels help keep a healthy immune system, and have a powerful potential to lengthen lifetimes.
Since 99% of a cup of tea consists of water, the quality of water used is important. Ancient Chinese masters used to amuse themselves by trying to guess the source of the water used to infuse the tea. Water laden with calcium oxide, magnesium, lead or chlorine, for example can cause a bleach aftertaste, hard, limestone-rich water should also be avoided if possible. The supposedly ideal water is pH neutral and contains a few minerals. Lu Yu in contrast claimed that “the most suitable water is from the same region as the tea,” because when in contact with the water that the tree drank all its life, the leaves true nature will reveal themselves.
Tea also facilitates digestion by stimulating the elimination of fats. On the other hand, it can inhibit the absorption of iron and calcium from foods. For this reason, drinking tea of any type with meals is not recommended, nor is drinking tea during the half hour before or after a meal.
Green tea has been used by traditional Chinese medicine practitioners to reduce heat, boost alertness, relieve headaches, help digestion, and more, successfully for many years.
Also according to recent studies, green tea appears to contain a higher number of polyphenols than other tea families. Green tea is also believed to contain more iron, vitamins and catechins than black tea, this and the higher polyphenol content is due to the dehydration method involved in the processing of green tea.
According to Chinese medicine, it helps to counteract excessive heat and alleviates the symptoms of menopause.
Regular consumption of oolong tea is said to have a slimming effect by stimulating the metabolising of lipids. Due to the high concentration of aromatic oil, which are drawn out of the leaves during rolling, oolong tea can have an anti-stress or even euphoric effect.
The enzymatic oxidation undergone by the leaves during the processing of black tea converts some of the catechins into theaflavins and thearubigins, as well as destroys some of the vitamins. But, the caffeine in black tea is released more rapidly into the bloodstream over a shorter period compared to green tea, as oxidation partially separates it from the tannins. This means that black tea is more effect as a physical stimulant than green tea.
Pu’er tea has long been used as a dietary supplement by nomadic tribes and ethnic groups living in regions of Asia, because of it specific properties. As these people ate mostly very fatty yak meat, tea allowed them to balance their diet, counteracting the fat. Pu’er teas are recognised as helping specifically to regulate the body and stimulate digestion. Pu’er is also known to eliminate cholesterol from the body.