Caffeine. Some people can't seem to get through the day without it. For others, it's as close to a morning breakfast as they'll ever have. It's use dates back to the stone ages according to some anthropologists and has come to be the most used drug in the world. Millions overuse caffeine which can cause symptoms such as nervousness and anxiety, hyperreflexia, and sleeplessness. In large doses or long-term exposure, respiratory problems and even heart palpitations can occur. And that's just for starters. Modern day uses of caffeine include its use in religious ceremonies to allow people to stay awake and remain alert in order to perform prayers and other religious rituals throughout the night. When coffee was introduced to the Europeans in the 16th century, its negative qualities were quickly realized and a failed attempt to ban its use ensued. By the 19th century caffeine was starting to appear in soda drinks, which were originally prescribed as health drinks, and beginning to take a firm hold on modern culture. Caffeine's widely accepted use comes from a general perception that it is harmless. And in smaller doses, caffeine appears to have very little, if any, negative side effects. The effects of caffeine in low doses end within a few hours. However, the short "high" of caffeine, which acts as an ergogenic giving the user a boost in physical and mental capacities, results in a continuing need to take it throughout the day. Continuous consumption of caffeine over a long period of time -- which many users experience due to its wide availability in soft drinks and energy drinks, making it nearly impossible to completely avoid it -- is when users start to experience ever increasing negative side effects. Headaches are often the first noticeable side effect, which typically happens when a person who has been a regular user stops taking it for a period of time. It doesn't take long to discover that returning to caffeine consumption will often prevent the so-called caffeine headache. When the simple act of drinking a soda is all that's needed to prevent a headache, users can quickly fall into the trap that results in a reliance on the drug. That is to say, the user becomes addicted. Furthermore, caffeine is a diuretic, which can lead to dehydration. The more caffeine a person takes in, the more dehydrated they become. Dehydration has the coincidental side effect of headaches as well and instead of hydrating oneself, a user will often continue taking in even more caffeine to prevent the headache which, in turn, aggravates the problem and can drive the user further into addiction.
Caffeine is a central nervous system and metabolic stimulant, and is used both recreationally and medically to reduce physical fatigue and restore mental alertness when unusual weakness or drowsiness occurs. Caffeine stimulates the central nervous system first at the higher levels, resulting in increased alertness and wakefulness, faster and clearer flow of thought, increased focus, and better general body coordination, and later at the spinal cord level at higher doses. The precise amount of caffeine necessary to produce effects varies from person to person depending on body size and degree of tolerance to caffeine. It takes less than an hour for caffeine to begin affecting the body and a mild dose wears off in three to four hours. Consumption of caffeine does not eliminate the need for sleep: it only temporarily reduces the sensation of being tired. With these effects, caffeine is an ergogenic: increasing the capacity for mental or physical labor. A study conducted in 1979 showed a 7% increase in distance cycled over a period of two hours in subjects who consumed caffeine compared to control tests. Other studies attained much more dramatic results; one particular study of trained runners showed a 44% increase in "race-pace" endurance, as well as a 51% increase in cycling endurance, after a dosage of 9 milligrams of caffeine per kilogram of body weight. The extensive boost shown in the runners is not an isolated case; additional studies have reported similar effects. Another study found 5.5 milligrams of caffeine per kilogram of body mass resulted in subjects cycling 29% longer during high intensity circuits. Caffeine is sometimes administered in combination with medicines to increase their effectiveness. Caffeine makes pain relievers 40% more effective in relieving headaches and helps the body absorb headache medications more quickly, bringing faster relief. For this reason, many over-the-counter headache drugs include caffeine in their formula. It is also used with ergotamine in the treatment of migraine and cluster headaches as well as to overcome the drowsiness caused by antihistamines.