Caffeine from natural sources has been consumed and enjoyed by humans throughout the world for centuries. The widespread natural occurrence of caffeine in a variety of plants undoubtedly played a major role in the long-standing popularity of caffeine incorporated products, especially the beverages.
The human body requires a certain amount of caffeine and research indicates that up to 8 cups of tea daily will not have any detrimental effect on the body. The species or the variety of the tea plant determines content of caffeine in tea, as it is a genetic feature. Camellia sinensis has caffeine levels of approximately 2.5 % to 4%. However the distribution of caffeine in the plant depends on the part of the plant it is derived from and the conditions that the plant is grown in.
The quantity of caffeine in tea, on dry solids basis, is more than the quantity of caffeine in an equal weight of dried coffee beans. However, as a result of getting more cups of tea from a unit quantity of black tea than from an equal quantity of ground coffee beans, the quantity of caffeine per cup of tea is less than the caffeine in an equal cup of coffee.
Excessive caffeine is said to have adverse effects on the human system and brewed tea has only half the caffeine levels in brewed coffee. However, it is important to note that research proves that the presence of caffeine in tea does not produce unhealthy results due to its combination with tea polyphenols.