Caffeine content of common beverages
1979
Recent studies show little variation in the caffeine levels of common beverages. A cup of tea brewed 3-5 minutes, a glass of iced tea, a cup of instant coffee, or a can of a carbonated beverage all have similar caffeine contents. However, the caffeine level in tea is considerably lower than that in brewed coffee. The difference in caffeine content depends on the product, brewing time, and preparation method. For example, the higher caffeine levels in coffee brews came from the finest grind and high levels in tea came from the bags with the smaller size of tea leaf parts. Caffeine is readily absorbed from gastrointestinal tract and is distributed in the various tissues of the body, passing rapidly into the central nervous system. Caffeine has been associated with restlessness and irritability in children and teenagers.
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