Caffeine and its Effects on the Human Body

Many of us feel tired without their needed cup of coffee in the morning. This is because the aromatic drink contains caffeine, a stimulant with an uplifting effect, which is also found in energy drinks, cola, and tea. In small quantities, caffeine is even found in cocoa. But how much caffeine is recommended per day and what does this substance trigger in our body?

What exactly is caffeine?

Caffeine is a natural substance and is found in various plants. Found in the fruit or the leaves, these plants use the substance to ward off pests. However, the psychoactive substance can also be found in seeds or even be produced synthetically to be added to drinks and food. Depending on the type of alkaloid, consumers can also find the substance under the names theine, guaranine, or methyl theobromine.

What physical effects does caffeine have on our bodies?

The consumption of stimulants causes the release of stress hormones. These are known as adrenaline and cortisol. As soon as the release occurs, the blood pressure begins to rise and the heart frequency increases. Depending on the amount of the substance, this can take between 15 and 30 minutes. The stimulating effect will then disappear after a few hours. This is because the psychoactive substance is excreted with urine.

In some people, alkaloid stays in the system for longer than in others. This is due to the individual metabolism rate which differs from person to person. The frequency of caffeine consumption is also a decisive factor. People who drink coffee and tea less frequently feel a stronger effect because they don’t experience a habitual effect. Similarly, the sensitivity to caffeine varies from consumer to consumer.

What positive effects do coffee and tea provide to us?

Most people feel more alert shortly after drinking a cup of coffee. But why does this happen? There are certain receptors in our brain which keep the active ingredient in coffee. This blocks these receptors and releases a messenger substance. This substance then determines the activities of the brain.

Only a mere 100 mg of caffeine can stimulate our ability to think and increases the coordination ability of our body. The sensation of pain is also reduced. This is because the blood vessels contract after drinking caffeinated drinks. For this reason, many people drink coffee or tea when they have headaches and migraines to relieve their pain.

When is it too much caffeine?

Caffeine also has a positive effect on athletically active people. The substance often has an endurance-enhancing effect before training. According to studies, 330 mg can already contribute to a significant increase in endurance. In sports such as rowing and cycling, this can lead to an increase in the endurance of 30 to 120 minutes.

According to the German Institute of Nutrition Research (DIfE), coffee can help prevent cancer. The consumption of four cups a day reduces the risk of liver cancer by about 75 percent. An even higher consumption does not lead to even lower risk, however, but to a more likely occurrence of overdose symptoms.

Can I develop a tolerance for the active ingredient caffeine?

People who consume higher doses of caffeine for a longer period can develop tolerance. This is because more receptors are formed in the brain, which in turn require more caffeine to be blocked. If the receptors are not blocked, the work of the nerve cells is slowed down. This habitual effect can occur after several days or weeks of heavy coffee consumption.

What happens when I stop drinking caffeine?

People who drink coffee on a regular and frequent basis may experience mild withdrawal symptoms.

These are reflected in the following points:

  • Mild headache
  • Tiredness
  • Reduced vigilance
  • Lack of energy
  • Fatigue

Less frequently, mood swings and a lack of concentration can occur. Occasionally, people also observe increased irritability. But after only two days, these symptoms are often a thing of the past. In some cases, however, it can take nine days before the withdrawal symptoms disappear.

What happens if I drink too much caffeine?

As a rule, adults are said to have overdosed if they consume one gram of caffeine per day. However, an excessive dose of the substance depends on many factors. These include weight, age, and also consumer behavior.

Usually, people notice an overdose of alkaloids when they experience a significantly higher pulse rate. Extrasystoles can also occur. Since caffeine is a psychoactive substance, there is also an occasional development of severe irritability and anxiety combined with sleep disorders if the consumption of coffee is more than moderate.

What is the optimal dose of caffeine for adults?

The German Federal Institute for Risk Assessment provides clear information, which is divided into daily and individual doses. Over a day, the Institute recommends not exceed 400 mg caffeine. Within the framework of a single dose, however, no more than 200 mg of the psychoactive substance is recommended. 200 mg of the substance is contained in about two cups of coffee.

Consumers who want to know exactly which amount is suitable for them should consider their weight as a factor. According to the Institute, it is saved to consume 5.7 mg of caffeine per kilogram of weight. People who weigh 100 kg can, therefore, consume 570 mg of caffeine per day, which corresponds to five to six cups of coffee. In comparison, the maximum single dose is three milligrams per kilogram of body weight. Nursing and pregnant women should note that half of the above-mentioned amounts are considered safe.

How much caffeine is safe for children and young people?

Besides coffee, even cocoa contains caffeine. Since cocoa and chocolate are frequently consumed by children, parents should know how much of the substance is harmless. For young people between 10 and 18 years of age, the EFSA recommends 0.4 to 1.4 mg of caffeine per kilogram of body weight. For children between the ages of three and ten, the maximum amount of the substance is 0.2 to 2.0 mg per kilogram of body weight. Infants between one year and three years of age may consume a maximum of 2.1 mg per kilogram of body weight. Babies should completely avoid caffeinated drinks and food.


The substance is associated with numerous health benefits. That is why many people turn to coffee, cola, and tea to improve their concentration ability or to relieve headaches. Also, consumers usually feel more alert after drinking one or two cups of coffee. However, if too much of the substance is consumed, undesirable effects such as sleep disorders or an increased heart rate can occur. Irritability also occurs sporadically. For adults, the recommended maximum dose of caffeine is 5.7 mg per kilogram of weight. In infants, children, and adolescents, the amount of this active ingredient varies greatly according to age. It is therefore recommended to follow the guidelines of the EFSA.

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