C8H10N4O2, this is the chemical formula of caffeine. Besides coffee, we can find caffeine in: soft drinks, mate tea, green tea, cocoa powder, and energy drinks. Caffeine, also called: methylxanthine, is present in various regions of the world.
A study conducted by the psychology department of UNIFESP proved that, yes, caffeine can be considered a drug, and due to its easy availability and widespread consumption, it is concluded that it is the most used drug in the world. A cup of coffee contains approximately 85mg of caffeine.
Caffeine appears in the form of a white powder (no, it is not black, brown, or chestnut as one might assume), crystalline, shiny in appearance, odorless, and with a very bitter taste. Naturally present in more than 60 plants, caffeine has been consumed and appreciated since ancient times, probably since the Paleolithic.
It is believed that coffee, as we know it today, originated in Ethiopia, spreading to the Arabian Peninsula and then to the rest of the world.
More interesting than the history of caffeine are its effects on the human body and the different uses people make of the substance. Everything in excess is harmful, and caffeine is no different; there are benefits and harms in using the drug. Caffeine is a stimulant, widely used in gyms as a “thermogenic,” that is, a metabolic accelerator, by 
accelerating metabolism, consequently increasing fat burning and producing a faster “weight loss,” in addition to making the body more resistant to muscle fatigue. Besides speeding up metabolism, it makes people more alert, affecting the discharge of nerve cells and the release of neurotransmitters and some hormones like adrenaline. A simple cup of strong coffee taken on an empty stomach can produce in a few minutes an increase in mental and sensory acuity, as well as raise energy levels, causing well-being and making the person more alert. Besides being used in gyms and in tasks that require attention, caffeine can be used to help with headaches, as it is a vasoconstrictor, inhibiting the effects of vasodilation that occur during migraines and headaches.
Loaded with polyphenols, a powerful antioxidant, caffeine, in moderate concentrations, combats cell aging and keeps people looking younger, in addition to improving mood, acting directly on nerve cells and the brain, maintaining a state of excitement and a feeling of rejuvenation.
However, it is not only benefits that occur with caffeine use; if consumed in excess, the drug causes digestive problems, such as gastric acidity, as it stimulates the production of digestive acids. Regarding digestive issues, it is not recommended to ingest the substance for those with osteoporosis or any calcium deficiency, as the presence of caffeine in the body hinders the absorption of the mineral. If you have trouble sleeping and frequently wake up in the middle of the night to go to the bathroom, avoid beverages that contain caffeine, as besides being a stimulant, the substance also acts as a diuretic. Remembering that caffeine has been labeled as a 
drug, therefore its chronic use can cause dependence, as cellular adaptations occur that lead to tolerance to the effects that caffeine produces. Those who consume caffeine chronically, when they reduce their intake, even if slightly compared to the amount they were used to, may experience headaches, lethargy, anxiety, and nervousness, explains the Nutritionist from the Albert Einstein Israelite Hospital, Tatiane Muniz Oliveira. A quick analysis can conclude that there are more benefits than harms in caffeine intake, but if consumed in moderation, we can almost completely enjoy only its positive effects, so, shall we have a coffee?
Source: www.crbm1.gov.br, by Murilo Camano Murr