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 10 – 12 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, the variety that is grown in Sri Lanka has caffeine levels of approximately 2.5 – 4%. However the distribution of caffeine in the plant depends on the part of the plant it is derived from.
Both tea and coffee contain the methylated xanthines, caffeine, theophylline and theobromine. Brewed coffee is said to have the highest caffeine content among those dietary items containing caffeine- approx. 100 mg per cup. A 300-ml bottle of cola has 30- 60-mg caffeine and approx. 37-mg caffeine is there in 56g dark chocolate bar. There are a wide variety of drug products that contain caffeine- typically 200 mg per tablet or capsule (pharmacologically active dose of caffeine). A cup of tea has approx. 28 –44 mg caffeine- (FDA 1980)
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.