Tea preparation and its influence on methylxanthine concentration

The amount of tea or coffee estimated from the number of cups consumed is frequently used as an indication of caffeine consumption in epidemiologic studies. However, this alone may be an inadequate indication of intake since drinking practices of tea varies. In this study, methylxanthine (caffeine, theobromine, and theophylline) contents in three brews of four types of tea (black, oolong, green, and herbal) in both bags and loose leaf forms were investigated to determine the actual amount of methylxanthines present in tea as a function of different brewing methods. On a dry leaf weight basis, total caffeine after three brews was highest in black (32.8 mg/g) and green (36.6 mg/g) tea leaves and lowest in Formosa oolong tea 2 (23.8 mg/g). Total theobromine was highest in black teas (1.64 and 1.69 mg/g) and least in oolong teas (0.65 and 0.71 mg/g). Caffeine and theobromine were not detected in either herbal tea samples, and theophylline was not detected in any tea tested. The overall average caffeine released in the first through third brews were 69%, 23%, and 8%, respectively. Three cups of tea brewed using three tea bags (Western culture) have approximately twice the amount of methylxanthines as the same volume prepared by three successive brews of loose tea leaves (Asian culture). These differences should be accounted for by the epidemiologic studies evaluating the effect of methylxanthines on health.