Nobody knows exactly, where or when, the first cup of tea was brewed. According to folklore, Emperor "Shen Nung" who reigned over China in 2732 BC discovered the stimulating effect of tea accidentally when wild tea leaves fell into his pot of boiling drinking water.
Chinese have probably been drinking tea in some form or the other since the fourth century AD and considering that wild tea grew in many parts of Assam, it is not unknowingly that tea drinking in India too is as old as in China. The raw material for tea manufacture normally consists of two young leaves and an unopened leaf bud-the famous "two leaves and a bud" formula, but, plucking of longer shoots containing 3 or even 4 leaves is not uncommon. The freshly harvested tea shoots can be processed into the various kinds of tea, namely,black tea, green tea, oolong tea and instant tea. In the manufacture of black tea(the usual tea that we drink),the material undergoes "fermentation" while in the production of green tea, delicate and subtle in flavour,fermentation is purposely omitted.Oolong tea leaves get an intermediate treatment,considered to be "semi-fermented".Instant tea,like instant coffee,is a dehydrated product containing only the soluble constituents of tea.
There is hardly any drink that is not a food too, in terms of calories it provides-tea is no exception. A cup of tea, containing 2 tbsp of milk and a tsp of sugar, yields about 40 calories. Milk contains casein, which makes the tannin in the tea insoluble, thus removing some of its astringency(acidic effect).Apart from the milk and sugar generally added, the tea infusion contains marginal quantities of vitamins and minerals, but no significant quantities of extractable proteins, carbohydrates or fats.
Tea is fairly rich in most of the B group vitamins. Apart from these, it is also a good source of vitamin E and K and Beta-carotene (changes into vitamin A in our body).Tea contains traces of minerals like Copper, Flouride and Manganese too. Fluoride helps in avoiding cavities in the teeth.
The accumulating scientific data on tea and its constituents - the vitamins, caffeine and tannin- and on its antibacterial activity provides a new picture of this popular beverage. Over the past few decades, the list of physiological disorders for which tea is contra-indicated has been steadily decreasing. On the other hand, caffeine is sometimes prescribed therapeutically for the treatment of hypertensive headaches and tea is a legitimate means of supplying this medication. Tannin destroys bacteria and virus, thereby inhibiting the growth of dental plaque. But at the same time, tannin inhibits the absorption of iron, calcium and zinc from the food, when tea is consumed along with food.