You may remember a brief coffee scare back in the early 1980s, when a single study linked coffee with pancreatic cancer. The many studies done so far have produced little in the way of coherent results. Researchers have had difficulty distinguishing the effects of caffeine from those of tobacco, which does increase the risk of bladder cancer and often goes along with heavy coffee drinking. Overall, a connection between coffee and bladder cancer, if it exists at all, likely applies only to true coffee junkies. A recent reanalysis of ten European studies found an increased risk only among people who drank ten or more cups a day.
Studies show that drinking coffee seems to have no influence on the risk of colon cancer.
It's such a powerful stimulant that the International Olympic Committee and the National Collegiate Athletic Association set limits on how much caffeine can remain in the blood during competition. In addition to boosting physical endurance, caffeine increases alertness and improves mood. The buzz sometimes comes at a price, though. People who drink more than they're used to may become restless, jittery, and unable to sleep. Moreover, it's possible to become physically addicted to caffeine within a matter of days.