About 50 percent of Americans drink coffee every day, at an estimated three to four cups per person, according to a 2009 CBSNews.com article. Its popularity is from the kick it provides, says Bennet Weinberg, author of two books on the beverage, arguing that without caffeine, coffee wouldn’t be nearly as popular. Caffeine is a stimulant that activates the central nervous system, but too much can quash your energy levels.
The jolt drinkers get when they consume coffee comes exclusively from the caffeine content. Caffeine is considered a drug that stimulates the central nervous system and increases energy and alertness. Some people receive a temporary boost in mood. Too much caffeine, however, can cause anxiety, headaches, nervousness and tremors. Those who have had a cup late in the day know that it can interfere with sleep. Drinking caffeine in moderate amounts, such as three 8-ounce cups of coffee or 250 milligrams a day, is considered safe according to the National Institutes of Health. Be aware that even as little as 100 milligrams a day can make you caffeine-dependent, according to KidsHealth.org. Without your daily fix, you could feel extremely fatigued and irritable.
Drinking a cup of coffee gives most people an initial burst of energy, but it’s not uncommon for that burst to be followed by an energy crash. After a few hours of operating on an artificial high, your body normalizes, and you might feel tired. After several hundred milligrams of caffeine, that fifth or sixth cup just can’t provide enough lift.
If you drink coffee throughout the day, you could be experiencing fluctuations in energy and alertness, which can lead to chronic adrenal exhaustion, according to a report in the July-August 2002 issue of "Psychosomatic Medicine." In the book “Caffeine Blues,” Stephen Cherniske explains that caffeine, regardless of whether the source is coffee or cola, takes effect by firing neurons in the brain. Excess neuron activity triggers the production of adrenalin – a hormone secreted by the adrenal glands. When the adrenalin wears off, your energy drops. When this process is repeated two, three or four times, your body is in a constant state of what Cherniske calls “caffeinism.” Symptoms include feeling tired, anxious, irritable and depressed. This process is also responsible for creating caffeine tolerance, which is why, for some, they can drink four cups of coffee and not feel any more energized than a person who drinks one cup.
Your coffee habit might be inadvertently responsible for your fatigue. While the experts suggest drinking your last mug several hours before bedtime, so as to not disturb your rest, the effect of the drug can linger in the system for hours. Some people are also very sensitive to the chemical. They might attribute their tossing and turning to daily stressors, but stress and anxiety are also side effects of caffeine. After several nights of sleeping poorly, people can develop a sleep deficit, which leads to feelings of fatigue, according to a 2010 article by "Newsweek."