Caffeine is arguably the world's most well-known psychoactive substance. Millions of people start their day with a cup of coffee or tea to stay alert and focused. But what exactly is caffeine? How is it produced in plants, and what chemical processes occur in the body when we consume it? In this article, we examine caffeine from three perspectives: chemical, botanical, and physiological.

Caffeine from a chemical perspective – structure and properties

Chemically, caffeine belongs to the xanthine group, a class of alkaloids found in many plants. Its chemical formula is C₈H₁₀N₄O₂, and its molecular structure consists of a purine ring system with three methyl groups.

The unique property of caffeine is its ability to act as an adenosine antagonist. Adenosine is a neurotransmitter that causes tiredness and relaxation in the brain. Caffeine blocks adenosine receptors, making us feel more alert.

Caffeine is water-soluble and has a melting point of approximately 235–238 °C. It is heat-stable, which is why it is not destroyed during the roasting of coffee beans. However, it can behave differently in different beverages—in tea, for example, it is partially bound to polyphenols and is therefore absorbed more slowly.

Botanical perspective – Why do plants produce caffeine?

Caffeine is found in many plants, particularly coffee, tea, cocoa, and guarana. But why do plants produce caffeine at all? In nature, caffeine primarily serves as a defense mechanism against pests. Caffeine is toxic to many insects because it disrupts their nervous system. This is how caffeine-containing plants protect themselves from predators. Interestingly, some plants also use caffeine to attract pollinators. Studies show that bees remember plants whose nectar contains small amounts of caffeine better. This improves their learning ability and ensures that they visit the same flowers more often—a benefit for the plant. The caffeine concentration varies depending on the plant and part of the plant. Coffee beans contain between 0.8% and 2.5% caffeine, depending on the variety.

Effects of caffeine on humans

Caffeine consumption has a variety of effects on the human body. The primary effect is stimulation of the central nervous system, but caffeine also affects the cardiovascular system, metabolism, and even the psyche.

Normally, adenosine binds to specific receptors in the brain and signals the body to relax and become tired. Caffeine has a similar structure to adenosine and can block its receptors – the result: we feel more alert and focused. Caffeine also stimulates the release of dopamine and norepinephrine. This improves mood, increases motivation, and can even temporarily enhance cognitive performance.

In addition to its effects on the brain, caffeine has numerous other effects. Caffeine can slightly increase blood pressure in the short term and stimulate the heart. It promotes fat burning and can slightly increase the body's basal metabolic rate. Caffeine stimulates the production of stomach acid, which can cause stomach problems in some people. Caffeine has a mild diuretic effect, but the body adapts to it, so this effect diminishes in regular coffee drinkers.

How long does caffeine last?

The half-life of caffeine in the body is approximately 4–6 hours, but varies from person to person. Factors such as genetics, age, and liver function play a role. Interestingly, some people metabolize caffeine more slowly due to genetic differences. They may drink a coffee in the afternoon and still be awake in bed that evening, while others can easily enjoy an espresso late at night without experiencing sleep problems.

Whether caffeine is good or bad depends largely on the dose and individual response. In moderate amounts (about 200–400 mg per day, or 2–4 cups of coffee), it can increase concentration, improve mood, and even reduce the risk of certain diseases such as Parkinson's or Alzheimer's. Too much caffeine, however, can have negative effects: tremors, restlessness, insomnia, or rapid heartbeat are typical symptoms of an overdose. People who consume caffeine only rarely or who are genetically metabolized more slowly are particularly susceptible.

Interestingly, the body develops a tolerance to caffeine relatively quickly. Regular coffee drinkers notice a diminished effect over time. Conversely, suddenly stopping caffeine can cause withdrawal symptoms such as headaches, fatigue, or irritability.

By the way: Did you know that Robusta coffee has almost twice as much caffeine as Arabica? So, enjoy your next coffee mindfully—now you know exactly what's in the beans!

---

Would you like to avoid caffeine in your coffee? Try our Popayan Reserve Decaf beans from Colombia. Available as an Omniroast.