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Caffeine and Tea: Five Considerations

1. The longer the tea leaves have fermented during manufacture, the greater their caffeine content. Green tea, which is unfermented, has one-third the caffeine per cup as black tea, which is fully fermented. Oolong is semi-fermented and has about half as much caffeine as black tea.

2. The shorter the brewing time, the less caffeine ends up in the cup. A four-minute infusion of black tea will produce 40 to 100 milligrams of caffeine, a three-minute infusion only about 20 to 40 milligrams.

CAFFEINE PER 6-OZ. CUP, IN MILLIGRAMS

3. The smaller the leaf, the stronger the extraction of caffeine. Using comparable amounts and brewing times, a tea bag filled with cut leaf or "dust" will release nearly twice as much caffeine per cup as full-leaf tea.

4. Caffeine's primary effects last about 15 to 45 minutes, depending on an individual's sensitivity.

5. Scientific studies of caffeine to date have been contradictory. There is no conclusive evidence that caffeine causes or exacerbates any specific illness or medical condition.