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All About Caffeine
Caffeine () is a bitter, white crystalline xanthine alkaloid and a stimulant drug
Caffeine is found in varying quantities in the seeds, leaves, and fruit of some plants, where it acts as a natural pesticide that paralyzes and kills certain insects feeding on the plants, as well as enhancing the reward memory of pollinators
It is most commonly consumed by humans in infusions extracted from the seed of the coffee plant and the leaves of the tea bush, as well as from various foods and drinks containing products derived from the kola nut
Other sources include yerba mat�, guarana berries, guayusa, and the yaupon holly.
In humans, caffeine acts as a central nervous system stimulant, temporarily warding off drowsiness and restoring alertness
It is the world's most widely consumed psychoactive drug, but unlike many other psychoactive substances, it is legal and unregulated in nearly all parts of the world
Beverages containing caffeine, such as coffee, tea, soft drinks, and energy drinks, enjoy great popularity
In North America, 90% of adults consume caffeine daily.
Part of the reason caffeine is classified by the Food and Drug Administration as generally recognized as safe is that toxic doses (over 10 grams for an average adult) are much higher than typically used doses (less than 500 milligrams)
Ordinary consumption has low health risks, even when carried on for years � there may be a modest protective effect against some diseases, including Parkinson's disease, heart disease, and certain types of cancer
Some people experience sleep disruption if they consume caffeine, especially during the evening hours, but others show little disturbance and the effect of caffeine on sleep is highly variable.
Evidence of a risk to pregnancy is equivocal, with some authorities concluding that it is wise for pregnant women to limit consumption to the equivalent of two cups of coffee per day or less
Caffeine has pressor and mild diuretic effects when administered to people who are not used to it, but regular users develop a tolerance to this effect, and studies have generally failed to support the common notion that ordinary consumption contributes significantly to dehydration
With heavy use, tolerance develops rapidly to autonomic effects such as elevated heart rate and muscle twitching, but not to the cognitive or arousal effects of caffeine
Chronic use can result in a mild state of caffeine dependence.