The Effect of Caffeine on the Human Body

Caffeine is a purine alkaloid that belongs to the methylamine group. It is a white powder with a bitter taste and has no odor. It does not accumulate in the human body and is excreted with urine in unchanged form and as a derivative of uric acid and xanthine. A cup of coffee contains 2 to 115 mg of this substance, while the lethal dose is 10 to 12 g. The average daily consumption of caffeine in Europe is 280 to 490 mg, with the highest consumption in Scandinavian countries due to high coffee consumption.

Caffeine is found in the following products: coffee (40 mg/100 g), tea (11 mg/100 g), cocoa (230 mg/100 g), and energy drinks (31 mg/100 g).

Caffeine is a rapidly absorbed compound that reaches its maximum concentration in the blood after 30-120 minutes of consumption, depending on individual body conditions and the presence of food in the stomach. It is not accumulated in the body but is metabolized in the liver to theophylline and theobromine. The effect of caffeine consumption is the blockage of adenosine receptors, which can be observed after 30-120 minutes of ingestion depending on individual body conditions and the presence of food in the stomach. Caffeine acts as a natural stimulant that enhances brain activity, reduces both physical and mental fatigue, and improves urine excretion. Caffeine blocks adenosine receptors A1 and A2, leading to a decrease in adenylate cyclase activity and a decrease in cAMP levels in cells. Furthermore, caffeine stimulates the production of neurotransmitters such as serotonin, GABA, adrenaline, and noradrenaline, improving brain function, having a stimulating effect, and facilitating cognitive processes. Consumption of more than 250 mg of caffeine per day leads to an increase in systolic and diastolic blood pressure by 5-15 mm Hg. Although the intake of this substance leads to a narrowing of blood vessels and an increase in peripheral resistance, it has no effect on the development of hypertension. In individuals dependent on large amounts of caffeine, no effect of caffeine intake on blood pressure has been found, despite the activation of the sympathetic nervous system. A reasonable intake of caffeine has no effect on the risk of developing cardiovascular diseases. No link has also been found between caffeine and the frequency of heart attacks or arrhythmias.

Caffeine is classified as a psychoactive compound due to its action on the central nervous system and the stimulation of dopamine receptors. However, frequent consumption of high doses of caffeine is not considered an addiction. Similar to cigarette or alcohol addiction, a constant supply of an active ingredient to the pleasure centers in the brain may be necessary for proper functioning. The American Psychiatric Association lists caffeine as a psychoactive substance, but not as a typical addictive drug. According to the International Classification of Diseases and Health Problems of the World Health Organization, symptoms resulting from excessive caffeine intake are classified as mental disorders and behavioral disorders caused by stimulant substances. Caffeine addiction is known as caffeinism and can manifest as restlessness, anxiety, irritability, excitement, muscle tremors, insomnia, headaches, increased urination, disturbed sensation, disturbances in the circulatory system (e.g., tachycardia or arrhythmia), and disturbances in the digestive system (e.g., nausea, vomiting, diarrhea). Withdrawal symptoms typically include fatigue, headache, weakness, drowsiness, decreased activity, difficulty concentrating, irritability, anxiety, nervousness, and flu-like symptoms. Excessive caffeine intake can be harmful to health, leading to overstimulation, tachycardia, and increased urination. Taking a single dose of >750 mg can cause intense thirst, tinnitus, visual disturbances, sleep disturbances (e.g., difficulty falling asleep, shallow sleep, and reduced sleep quality), as well as atrial or ventricular fibrillation. Caffeine can also affect the progression of stomach or duodenal ulcers. Individuals who need to follow a light diet for various reasons should avoid caffeine. During pregnancy, consumption of coffee and other caffeinated products should be limited, as high doses of this substance can have teratogenic effects and impair intrauterine fetal growth and skeletal mineralization.

The safe amount of caffeine that does not cause harmful reactions in humans is a maximum of 400 mg per day, which corresponds to a maximum of 2-3 cups of coffee per day. However, it is important to note that each person has different genetic and metabolic predispositions, so individual conditions of each person should be taken into account. Exceeding 500-600 mg of caffeine per day may cause unwanted side effects. Long-term consumption of caffeine can lead to disorders related to the kidneys, muscles, and digestive system. Taking a very high dose of caffeine (>7 g) can even lead to death, although such cases are very rare. Caffeine in small amounts and taken occasionally does not have negative effects on health. However, an excess of this substance can lead to addiction and negative effects on the body.