China has the history of “curing diseases with tea”, there are many records about curing diabetes, dysentery, cold-catch with old tea among the people in ancient China . Modern western medicine thinks that polyphenols, pigments, polysaccharides, saponins, amino acids, alkaloids, and inorganic elements in tea have health care function to human body. Tea is a kind of special beverage that can strengthen the immunity of Hunan body. Tea is a kind of special beverage that can strengthen the immunity of hunan body, resist oxidization and aging, prevent cancer, reduce blood fat and cholesterol, adjust metabolism, so tea has been generally acknowledged as healthy beverage in the 21 st century in tea and medical science circles all over the world.

The main functional composition of dark tea is tea polysaccharides compound. This kind of compound is regarded in medical science circle that it can adjust sugar metabolism (prevent and cure diabetes) ,reduce blood fat and high blood pressure, resist thrombasis and improve immunity of human body. Clinical experiments have proved that these special functions of dark tea are remarkable, which can't be replaced by other kings of tea.

Pile-fermenting of dark tea can make the big-molecular compounds in tea decompose and fission, and secrete the small-molecular compounds helpful to the quality of tea through the metabolism of itself under the participation of useful microbes, such as Candida, Aspergillus niger and bacteria, etc., and make tea taste coordinated and liquor color deep etc. Drying dark tea by smoke-baking with pine wood can further improve the quality of tea, and make tea products high in aroma, mellow in taste and deep red in liquor color.

Hunan dark tea has unique quality and remarkable pharmacological effects, this is because the processing of dark tea is different from that of other kinds of tea, among which pile-fermenting is the foundation of quality formation of dark tea, and smoke-baking with pine wood further promotes the formation of color, aroma and taste of dark tea products. The process of fungus-growing of Fu brick tea is the characteristic technique distinguished from other dark tea, which can not only improve the color, aroma and taste of the tea products, but also make them produce magical medical efficacy, so Fu brick tea is generally acknowledged as “The mysterious Tea on the Ancient silk Road of China”, and widely concerned in tea and medical sciences circles all over the world.

Fungus-growing is characteristic technique of Fu brick tea, which means in a certain condition of temperature and moisture, makes the superior fungus, Eurotium Cristatum grow and reproduce in brick tea. Eurotium Cristatum is one kind of fungi which is non-poisonous to human body, and can produce a series of functional chemical active substance beneficial to health, such as fat-decomposing enzyme, protein-resolving enzyme, -starch enzyme and so on, the clinical experiments have proved that Fu tea has remarkable effect on lowering fat and hypertension.

The formation of quality and functional composition of dark tea is a process of complicated chemical change. The theory of traditional Chinese medicine holds that “tea is good medicine of many diseases”. The theory of long storage of dark tea is the same as that of many traditional Chinese medicines can't produce efficacy until through after-treatment. It is un-objective and unjust to analyze the effect of a certain kind of composition on quality and function isolatedly and lopsidedly. Tea is just tea, it can't be replaced by vitamin tablets and amino acids.