The consumption of coffee and other caffeinated beverages is an integral part of everyday life for many people. This is mainly due to the stimulating effect of caffeine. However, this can also be a disadvantage and, for example, impair sleep quality. Therefore, when enjoying these drinks, it is important to consider the duration of caffeine’s effect and, ideally, to know individual characteristics.
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At a Glance: How Long Does the Effect of Caffeine Last?
- Caffeine is produced by plants as protection against insects and is popular as a stimulant among people all over the world.
- Caffeine takes effect after about 15 to 30 minutes and normally has an approximate half-life of three to five hours.
- Depending on the dose, caffeine can still impair sleep quality even if consumed six hours before bedtime.
- Defective CYP1A2 genes lead to about 59 percent of the population not being able to break down caffeine properly.
- Healthy people can consume up to 400 milligrams of caffeine per day. This corresponds to about 500 milliliters or just under two normal cups of coffee.
What is Caffeine?
Caffeine is one of the purine alkaloids. The naturally occurring organic compound is formed by certain plants to protect themselves from insects. Overall, the active ingredient is found in over 60 different plants. It can also be produced synthetically if necessary.
Caffeine is naturally found in, among other things:
- Guarana
- Coffee beans
- Cocoa beans
- Kola nuts
- Tea leaves
What Effect Does Caffeine Have on the Body?
From a chemical point of view, caffeine is similar to the nucleoside adenosine. This organic molecule is a byproduct of the exchange of messenger substances and energy consumption of nerve cells. The more active the nerve cells are, the more adenosine is produced. It binds to certain receptors on the nerve pathways of the brain. This gives the nerve cells the signal to work less. This prevents the organism from becoming overloaded. If caffeine is added to the body, it blocks the adenosine receptors. This means that the nerve cells remain active. The body apparently does not tire and the brain can work in a concentrated manner for longer.
Possible Side Effects of an Overdose
In moderate doses, caffeine makes you more alert. It also improves physical performance and concentration. However, in case of an overdose, it can also have undesirable side effects.
Possible consequences of excessive caffeine intake include, for example:
- Excitability,
- Palpitations,
- Nervousness,
- Insomnia and
- Sweating.
How Quickly Does Caffeine Work?
When enjoying coffee, one often has the impression that it makes one awake while drinking it. However, this is a pure placebo effect. Nevertheless, the human body absorbs orally ingested caffeine very quickly. It usually takes 15 to 30 minutes for the caffeine to be in the blood and for its effect to unfold. The effect usually reaches its peak after one to two hours.
How Long Does the Effect of Caffeine Last?
The half-life of caffeine is three to five hours. After this period, half of the caffeine contained in the coffee is still in the body. Accordingly, the effect can last for many hours. For example, a 2013 study found that a 400 mg dose of caffeine six hours before bedtime can significantly affect sleep.1
Caffeine Does Not Affect Everyone the Same
In some cases, the effect even lasts significantly longer than the six hours mentioned for various reasons. For example, pregnant women are particularly sensitive to caffeine. The increased concentration of the hormones progesterone and estrogen inhibits the formation of the enzymes that break down caffeine in their bodies. Therefore, the half-life, and thus the duration of effect, can be significantly longer in their case.
Other Factors Influencing the Duration of Effect
In addition to pregnancy, the following factors, among others, can affect the duration of caffeine’s effect:
- Age
- Body weight
- Liver health
- Medications
- Smoking
How Genes Influence the Effect of Caffeine
The invigorating effect of the caffeine contained in coffee is often quite desirable. Nevertheless, it is ultimately a toxin that the body wants to excrete quickly. How well it manages to do this depends to a large extent on genetics. The CYP1A2 genes are responsible for recognizing and neutralizing harmful substances such as caffeine.
Each person inherits one CYP1A2 gene from their mother and one from their father. If both CYP1A2 genes function normally, the caffeine is neutralized and excreted very quickly. However, this is only the case for 41 percent of the population. 44 percent of people have only one functioning CYP1A2 gene. In 15 percent, both genes are even defective.
Coffee Is Not Healthy for Everyone
In people with two functioning CYP1A2 genes, not only does the stimulating effect last for a shorter time. They also benefit particularly from the numerous healthy ingredients contained in their morning cup of coffee.
- For example, a 2006 study found that regular coffee consumption can reduce the risk of a heart attack in these individuals. In contrast, with one or two defective CYP1A2 genes, coffee can increase the risk of a heart attack.2
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How Much Caffeine Per Day?
According to the EFSA, the European Union agency responsible for food safety, a caffeine intake of:
- up to 200 mg (approximately 3 mg/kg body weight) as a single dose and
- up to 400 mg (approximately 5.7 mg/kg body weight) distributed throughout the day
is considered safe for healthy adults. For pregnant and breastfeeding women, the recommendation for the maximum daily dose is reduced to 200 mg of caffeine. More caffeine can potentially pose a risk to the baby. 3
Caffeine Content in Different Beverages
| Beverage | Caffeine content per 100 ml |
| Espresso | 110 mg |
| Coffee | 80 mg |
| Black chocolate | 50 mg |
| Energy Drink (Red Bull) | 32 mg |
| Cappuccino | 27 mg |
| Black Tea | 25 mg |
| Milk chocolate | 20 mg |
| Latte Macchiato | 11 mg |
| Green Tea | 10 mg |
| Coca-Cola | 9 mg4 |
Important to know: The actual caffeine content in natural products such as coffee and tea depends on factors such as the variety and preparation method.
When Should You Drink Your Last Cup of Coffee?
When it is best to enjoy your last coffee varies from person to person. However, in most people, caffeine no longer has an effect in the evening if they drink a coffee at 12 noon. Only in individual cases can it still affect sleep quality. If you are aware of this and still don’t want to forgo the hot beverage, it is best to opt for decaffeinated coffee.
Is Green or Black Tea a Suitable Alternative to Coffee?
Black and green tea contain less caffeine than coffee. In addition, thanks to the tannins also contained in tea, it enters the body more slowly. Nevertheless, it can have a stimulating effect. Therefore, neither black nor green tea is suitable as an alternative to a cup of coffee in the evening.
- 1 Christopher Drake, Ph.D., F.A.A.S.M., Timothy Roehrs, Ph.D., F.A.A.S.M., John Shambroom, B.S., Thomas Roth, Ph.D.: Caffeine Effects on Sleep Taken 0, 3, or 6 Hours before Going to Bed (Veröffentlichung: 15.11.2013). URL: https://jcsm.aasm.org/doi/10.5664/jcsm.3170 (zuletzt aufgerufen am: 30.08.2024). Die Studie fokussiert sich auf die Auswirkungen von Koffein auf den Schlaf, wenn es zu unterschiedlichen Zeiten vor dem Schlafengehen konsumiert wird (0, 3 oder 6 Stunden vorher.) Marilyn C Cornelis, Ahmed El-Sohemy, Edmond K Kabagambe, Hannia Campos
- 2 Affiliations Expand: Coffee, CYP1A2 genotype, and risk of myocardial infarction (Veröffentlichung: 08.03.2006). URL: https://pubmed.ncbi.nlm.nih.gov/16522833/ (zuletzt aufgerufen am: 30.08.2024). Der Artikel untersucht den Zusammenhang zwischen Kaffeekonsum, genetischer Veranlagung (CYP1A2-Genotyp) und dem Risiko eines Herzinfarkts (Myokardinfarkt).
- 3 European Food Safety Authority: EFSA erklärt Risikobewertung: Koffein (Veröffentlichung: 2015). URL: https://www.efsa.europa.eu/sites/default/files/corporate_publications/files/efsaexplainscaffeine150527de.pdf (zuletzt aufgerufen am: 30.08.2024).
- 4 Statista: Koffeingehalt verschiedener Getränke pro 100 Milliliter (Stand: November 2023). URL: https://de.statista.com/statistik/daten/studie/198116/umfrage/koffeingehalt-verschiedener-getraenke/ (zuletzt aufgerufen am: 30.08.2024).
