About half of all Americans drink 3.3 cups of coffee on any given day. Caffeine is found in coffee, tea, cola nuts, mate and guarana. It increases alertness and creates a feeling of mild euphoria. Jasmine Stuart drinks a mocha at Sacred Grounds. According to the Web site, caffeine increases heart rate, respiration, metabolic rate and the production of stomach acid and urine.
Caffeine also decreases reaction time to visual and auditory stimuli.
Cynthia Kuhn, Scott Swartzwelde and Wilkie Wilson of the Duke University Medical Center said caffeine can cause irregular heartbeats in some individuals. Caffeine is sometimes known to cause panic attacks and actually increases stress by increasing the amount of adrenaline in the body during stressful situations. However, its effects vary from person to person, depending on people's sensitivity to it, their metabolism and whether they smoke or take medication. Caffeinism, a serious caffeine overdose, is very rare but possible after ingesting extemely large amounts of caffeine. A positive effect of caffeine is its usefulness in relieving headaches, especially migraines.