Caffeine – the Natural Wake-Up Call
Do you know that sleepy feeling in the morning? Some grown-ups drink coffee or tea then. Inside is a substance called caffeine.
1. What Exactly Is It?
Caffeine is a natural substance. This means it occurs in plants and is not made by humans. Caffeine is a small molecule found in the leaves, seeds or fruits of certain plants. When people eat or drink these plant parts, caffeine enters their body. There, it affects the brain and muscles. It can make people feel more awake and help muscles perform for slightly longer. But caffeine is no magic potion. It does not make anyone smarter or stronger than they really are. Researchers have studied caffeine’s effects in many studies. For example, they have tested how caffeine affects performance in sport. In a study titled Caffeine and Cognitive Functions in Sports: A Systematic Review and Meta-Analysis, researchers combined many investigations focusing on cognitive tasks during sport. Another study, Time course of tolerance to the performance benefits of caffeine, examined whether the body becomes accustomed to caffeine. The researchers found that the effect can diminish over time if caffeine is consumed frequently. This is called tolerance. Caffeine is therefore an intriguing substance that science has not yet fully unravelled.
2. Where Does It Come From?
Caffeine is found in many plants. The best-known sources are coffee beans, tea leaves and cocoa beans. It is also present in the leaves of the yerba mate shrub and the seeds of the guarana shrub. These plants produce caffeine as a defence against animals that might eat their leaves. For the plants, caffeine acts as a protective compound. Humans discovered long ago that they could make drinks from these plant parts. Coffee is made from coffee beans, tea from tea leaves and chocolate from cocoa beans. All these beverages and foods contain caffeine, though in different amounts: a cup of coffee contains more caffeine than a cup of tea, and chocolate contains only small amounts. Researchers have also investigated how the body absorbs caffeine. This depends on individual sensitivity and how often caffeine is consumed. Some people react strongly to caffeine, while others barely notice it. Part of this variation is genetic. In a study titled CYP1A2 Genotype Variations Do Not Modify the Benefits and Drawbacks of Caffeine during Exercise: A Pilot Study, researchers examined whether certain gene variants alter caffeine’s effects during exercise. They found no clear differences, but this is not yet certain.
3. What Are Researchers Investigating?
Researchers want to understand exactly how caffeine works. For example, they have studied whether caffeine improves performance in sport. In a study titled The Effects of High Doses of Caffeine on Maximal Strength and Muscular Endurance in Athletes Habituated to Caffeine, researchers tested how high doses of caffeine affect strength and endurance in athletes accustomed to caffeine. Another study, Women Experience the Same Ergogenic Response to Caffeine as Men, examined whether women and men respond to caffeine in the same way. The researchers found that both sexes can benefit similarly. Caffeine has also been studied in cyclists: in the study Effects of caffeine on neuromuscular fatigue and performance during high-intensity cycling exercise in moderate hypoxia, researchers investigated how caffeine influences muscle fatigue during intense exertion when oxygen levels in the air are low. Many studies suggest that caffeine can slightly improve performance. However, open questions remain: How strong is the effect? Is it the same for everyone? And how exactly does caffeine act in the brain? These questions are still to be answered. Researchers continue to work on clarifying them.
4. A Thought Experiment
Imagine you are at a swimming pool and want to swim one length. You feel a bit tired. Now you have a drink containing caffeine. Do you think you would swim faster? Researchers have found that caffeine can slightly improve performance in some sports. But it does not turn you into a superhero. It may also make you feel more awake, leading you to think you are faster even if you are not. This is an interesting idea: sometimes things feel different from how they really are. Researchers try to measure this precisely. They have athletes perform the same task once with caffeine and once without, then compare the times. This way, they can determine whether caffeine truly helps or if it is just a placebo effect. What would you think if you swam faster? Would you attribute it to the caffeine or to your own effort?
For adults and professionals: the detailed page on caffeine
Frequently Asked Questions
Is caffeine dangerous for children?
Caffeine is a substance that affects the body. Children are often more sensitive than grown-ups. That is why children should not have too much caffeine. A small amount, like in a piece of chocolate, is usually fine. But too much can make you feel restless or have trouble sleeping.
Why does caffeine keep you awake?
Caffeine fits into certain spots in the brain. There it blocks a substance that makes us feel tired. This makes us feel more awake. But the body gets used to it over time. Then caffeine does not work as strongly. This is called tolerance.
Can caffeine help with sports?
Researchers have looked at whether caffeine improves performance in sports. In some studies, athletes with caffeine could keep going a bit longer or concentrate better. But the effect is not the same for everyone and not very big. Caffeine is no replacement for training.
Every statement on this page carries its evidence tier — proven, plausible or hypothesis — and leads to the original work. The decision in the individual case rests with the practitioner; we provide the connections.