The earliest caffeine consumption dates back to the Stone Age, when people would chew bark, seeds, or leaves of certain trees for increased energy and awareness. A naturally occurring substance, caffeine is a stimulant in humans, and is the most widely consumed psychoactive drug in the world. Because caffeine causes tolerance to build leading to increased consumption, people must be careful to ingest sensible amounts, especially because caffeine is readily available in so many drink products. Caffeine in moderation can be a great way to boost energy and mood; however, overuse can have very serious health implications.

Caffeine is a plant alkaloid found in many different plant species (over 60!), and acts as a pesticide, killing or paralyzing insects that try to feed upon the plant’s leaves. In addition to coffee and tea, caffeine also comes from the yerba mate and guarana plants which are often used to make energy drinks and weight loss supplements. Caffeine from a yerba mate is called mateine; from a guarana plant it is called guaranine. Ninety percent of Americans over the age of eighteen consume caffeine every day; it is one of the only psychoactive drugs to remain unregulated and legal throughout the world.

Acting on the central nervous system, caffeine is absorbed by the stomach and small intestines less than an hour after ingestion. First causing elevated awareness, improved body coordination, and clarity of thought, caffeine crosses the blood-brain barrier and inhibits adenosine receptors in the brain. The result is increased dopamine levels; dopamine is the brain’s pleasure system, so the increase in dopamine is what causes the caffeine ‘high.’ The inhibition of adenosine also leads to increased epinephrine, which stimulates the sympathetic nervous system during perceived threat. Epinephrine will increase blood flow to the heart and muscles, decrease blood flow to the skin and organs, and cause the liver to release glucose. Studies have shown a large increase in endurance of runners who take caffeine as opposed to those who do not, and this can be attributed to the increased epinephrine.

Though caffeine is fast-acting, it is very slow to leave the body, with a half-life of three to four hours (half-life is the time it takes for one half of the total caffeine amount to be eliminated by the body). Women on oral contraceptives, women who are pregnant, and anyone with liver disease will take even longer to digest caffeine. In pregnant women, the half-life of caffeine is nine to eleven hours, meaning that the drug will stay in a pregnant woman’s body for nearly one full day.

Caffeine tolerance can develop very quickly, and the brain will adapt to the presence of caffeine by increasing adenosine receptors. This increase in receptors reduces the stimulatory effects of caffeine (known as tolerance), and makes the body more sensitive to adenosine so that when caffeine usage is stopped, the body will feel symptoms of withdrawal. It can take less than eighteen days of continuous caffeine use to develop complete tolerance, while the effects of withdrawal will begin to show twelve to twenty-four hours after discontinuation of caffeine intake. Symptoms of withdrawal include headache, irritability, fatigue, and even stomach ache. In severe cases, reduced dopamine and serotonin levels in the brain can lead to mild depression.

Interestingly enough, overuse of caffeine can result in sleep disorders, anxiety, and even death. When used in large amounts over extended time period, caffeine can lead to peptic ulcers, muscle twitching, insomnia, and heart palpitations. In some individuals, caffeine usage will cause panic attacks, obsessive-compulsive disorders, and even phobic symptoms. In cases of extreme overdose, such as can happen with the snorting of caffeine powder or ingestion of caffeine pills, death can occur from ventricular fibrillation, where the heart fails due to lack of coordination between the heart chambers. It is nearly impossible to reach lethal levels of caffeine with the consumption of regular brewed coffee.

While caffeine in moderation is harmless, the long term benefits of caffeine consumption are still being discovered. Several studies have shown a decreased risk for Parkinson’s disease in men who consume caffeine, but studies in women are still unpersuasive. Other studies show that caffeine has a positive effect on short term memory, but it is unclear whether the positive effect only lasts while the caffeine is in the system, or whether it continues after the caffeine has been eliminated.

The world’s primary source of caffeine is the coffee bean, which was discovered centuries ago in what is now considered Africa. A trend that started long ago, caffeine usage has a universal appeal to people needing that boost of energy to start each day. We must remember however, to take precaution in today’s hustle and bustle society to use caffeine in moderation. Overuse can have very undesirable effects, and nothing can make up for lack of a good night’s sleep.