The effects of caffeine on various body systems: a review.

Caffeine is the most widely consumed drug in Western society. The intake of caffeine-containing beverages in many adults and children often reaches levels that can induce pharmacological effects. Ninety-nine percent of ingested caffeine is absorbed and distributed to all tissues and organs. The effects of caffeine intake differ greatly according to acute or chronic intake, level of intake, and the development of tolerance. Caffeine administered acutely to non-users or recent abstainers can induce hypertension, arrhythmias, altered myocardial function, increased plasma catecholamine levels, plasma renin activity, serum cholesterol levels, increased production of urine, gastric acid secretion, and alterations in mood and sleep patterns. Tolerance to chronic caffeine intake develops in most individuals, with the cessation of its effects on the renal system, the cardiovascular system, the gastrointestinal system and, to some extent, the central nervous system. Moderate caffeine consumers probably need to have little concern for the effect of caffeine intake on their health if their other life-style habits are also moderate.