Anna West, Sleep Performance Coach
‘Caffeine’s a friend when timed right, an enemy when it isn’t. Never on an empty stomach — otherwise you’ll crash.’
Caffeine – the world’s most popular stimulant
Dr. Lutz GraumannRegeneration Expert
In this article
It’s the world’s most widely consumed psychoactive substance — and one of the most effective when used correctly. It blocks fatigue signals in the brain, boosts concentration and stamina and can help combat jet lag. The key factor isn’t the quantity, but the timing. Find out what this means in practice here.
Key facts at a glance
- Effect: caffeine blocks the fatigue hormone adenosine in the brain. You become more alert, focused and productive. Onset: 15–30 min; duration: 3–7 h.
- Daily dose: max. 400 mg for healthy adults (EFSA). Equivalent to approx. 4 cups of filter coffee. Pregnant people: max. 200 mg.
- Sport: 3–6 mg/kg body weight, 30–60 min before training. Performance improvement of 5–10 per cent possible.
- Travel and jet lag (new): after westbound flights (Europe → USA), consume caffeine specifically on the morning of arrival to help reset your internal clock more quickly. Never on an empty stomach and never less than 8–10 h before sleeping.
- Avoid alcohol with caffeine as both disrupt sleep architecture.
- Timing is everything: caffeine’s your friend when timed right, your enemy when it isn’t. The quantity is often less important than the timing.
Whether in your morning coffee, afternoon black tea or as an energy drink before training — for many of us, caffeine is our daily energy boost. Perhaps you, too, regularly reach for a cup or a can to get through the day feeling more alert, focused or simply in a better mood.
For centuries people around the world have enjoyed caffeinated drinks — from traditional tea ceremonies in Asia, through the Arab coffee trade to modern coffee-to-go. What began as a drink for pleasure and as part of cultural traditions is now an integral part of everyday life for millions — whether in a cosy get-together, as a break-time ritual or as a quick pick-me-up on the go.
In this article, you’ll learn how caffeine affects the body, how much is in coffee, tea and energy drinks, the evidence on its health effects and how you can manage your intake. You’llalso discover caffeine-free alternatives that still give you a boost — without sleep problems or heart palpitations.
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01
What is caffeine and where is it found?
We know you value a clear mind and steady focus, so we've crafted our products to deliver the lift you need without the jitters. Caffeine is a naturally occurring, slightly bitter-tasting substance that belongs to the alkaloid group. Chemically speaking, it's a nitrogen-containing compound produced by certain plants as a natural defence against insects. For us humans, caffeine primarily has a stimulating effect on the central nervous system, which is why it's so popular as a stimulant.
Caffeine was first isolated in 1819 by the German chemist Friedlieb Ferdinand Runge, and we now know it occurs in over 60 plant species.
Natural sources of caffeine
- Coffee: 60–100 mg per cup. The content varies depending on the bean, roast and preparation method.
- Black and green tea: 30–60 mg per cup. Often referred to as ‘theine’.
- Cocoa contains only a small quantity of caffeine but does provide theobromine, which has a similar yet milder effect.
- Mate: approx. 20–30 mg per cup. A traditional South American drink.
- Guarana contains particularly high levels of caffeine and is often found in energy drinks and dietary supplements.
- Cola and energy drinks usually contain added caffeine as an extract or in synthetic form.
02
The effect of caffeine on the body
It’s widely enjoyed because it helps you feel more alert, focused and capable of higher performance. In the brain it blocks the receptors for the sleep-inducing hormone adenosine, which keeps the nervous system more active, causes a slight increase in heart rate and metabolism and makes you feel more energised. It also stimulates the release of dopamine and noradrenaline.
Key benefits at a glance
- Concentration and alertness: sustain focus for longer when you work or study.
- It can also temporarily boost endurance and strength when you exercise.
- Metabolism and fat burning: slightly increased energy expenditure, particularly when combined with exercise.
- Mood: The rise in dopamine often leaves you feeling more motivated and in a more positive frame of mind.
You’ll usually feel the first effects after 15–30 min, they’ll peak after 30–60 min and they typically last 3–7 h, though this varies from person to person.
Evening routines
Fall asleep more easily
03
Caffeine content comparison
Caffeine isn’t just found in coffee. Tea, cola, energy drinks and even cocoa also contain this stimulant — though in very different quantities. The exact caffeine content depends heavily on how the drink is prepared, the variety and the portion size.
Caffeine content of selected drinks per serving
Drink | Serving size | Caffeine content (average) |
Filter coffee | 200 ml | 60–100 mg |
Espresso | 30 ml | 30–50 mg |
Black tea | 200 ml | 30–60 mg |
Green tea | 200 ml | 20–50 mg |
Cola | 330 ml | 30–50 mg |
Energy drink | 250 ml | 80 mg |
Hot chocolate | 200 ml | 5–15 mg |
mate tea | 200 ml | 20–30 mg |
All figures are averages and may vary depending on the brand, variety and method of preparation.
How preparation affects caffeine content
- Coffee: the type of bean, grind size, roast and brewing time all have a significant influence. Longer contact between the water and the ground coffee (e.g. with a French press) increases the caffeine content.
- Tea: steeping time and water temperature play a major role — longer steeping times release more caffeine.
- Energy drinks and cola: the caffeine content is set by the manufacturer but may vary depending on the brand.
- Cocoa contains only a small amount of caffeine but more theobromine, which has a gentler effect.
Keep an eye on your total intake — several cups of tea, a cola and an energy drink can quickly add up to the recommended daily amount.
04
How much caffeine a day?
The safe amount depends on your individual sensitivity, your state of health and your lifestyle. The European Food Safety Authority (EFSA) recommends a maximum of 400 mg of caffeine per day for healthy adults — this is equivalent to around four cups of filter coffee or five to six cups of black tea. For pregnant or breastfeeding people, the guideline is a maximum of 200 mg per day (EFSA, 2015).
💡 Good to know.
Regular consumption in moderate quantities is well tolerated by most people. Listen to your own body — sleep problems, nervousness or a racing heart are signs that you may be having too much.
Is caffeine healthy for your health?
There's extensive research on caffeine — and the findings are mixed:
- Heart and circulation: According to one study, moderate caffeine consumption isn’t associated with an increased risk of cardiovascular disease. However, for some people with cardiac arrhythmias, reducing intake may be advisable (Zhong et al., 2021).
- Metabolism: studies show that caffeine can slightly increase energy expenditure and fat burning in the short term but the long-term effect is small.
- Cancer: The World Health Organisation (WHO) doesn't classify caffeine as carcinogenic and some research suggests a lower risk of certain cancers, such as liver or bowel cancer, with moderate coffee consumption.
For healthy adults, caffeine in moderation can be part of a healthy lifestyle. Know your own tolerance and manage your intake so it doesn’t interfere with sleep or your wellbeing.
05
Too much caffeine – symptoms and risks
Caffeine can have positive effects in moderate quantities – but too much of it can throw your body out of balance. Above a certain quantity, the downsides outweigh the benefits, and in sensitive individuals, side effects can occur even with smaller quantities.
Typical symptoms of excessive caffeine consumption
- Nervousness and restlessness: your nervous system is working overtime, leaving you feeling irritable or restless.
- Sleep disturbances: Caffeine can delay falling asleep and reduce sleep quality – even if consumed hours before going to bed.
- Heart palpitations and increased blood pressure: due to its stimulating effect on the cardiovascular system, you may experience noticeable heart palpitations.
Dependence and withdrawal
Regular, high caffeine consumption can lead to mild physiological dependence. Withdrawal symptoms usually occur 12–24 h after the last dose and may include:
- Headache
- Tiredness
- irritability
- Difficulty concentrating
These symptoms are unpleasant but usually subside after one to three days.
Risk of overdose
An acute caffeine overdose is rare but can have serious consequences. Symptoms include:
- Rapid heartbeat, tremors
- Nausea, vomiting
- Dizziness, anxiety
- In very high quantities (more than 1–1.5 g of caffeine at once), even seizures or cardiac arrhythmias
⚠️ Guideline:
The EFSA considers a single dose of up to 200 mg and a maximum daily intake of 400 mg of caffeine to be safe for healthy adults. If you regularly exceed these levels you're more likely to experience adverse effects — especially if you have existing heart problems or sleep disorders.
06
Caffeine metabolism and caffeine sensitivity
Not everyone reacts to caffeine in the same way – and this has a lot to do with how quickly or slowly your body breaks it down. This process takes place mainly in the liver, where a specific enzyme processes the majority of the caffeine.
How long does caffeine stay in the body?
The so-called half-life of caffeine — that is, the time it takes for half the quantity consumed to be broken down — is between 3 and 7 h for most adults. This means that if you consume 200 mg of caffeine at 3.00 pm, there may still be around 100 mg in your blood by 9.00 pm.
Several factors influence how quickly your body breaks down caffeine:
- Genetics: Some people break down caffeine more quickly while others do so more slowly.
- Age: as you get older your metabolism slows down – so caffeine stays in your body for longer.
- Pregnancy: during pregnancy, the half-life can increase to 8–10 h.
- Medication and liver health: certain medicines (e.g. some antibiotics, antidepressants) or liver conditions slow down the breakdown process.
- Smoking: nicotine can speed up the breakdown of caffeine, so the effects last for a shorter time.
Genetic differences and age-related factors
Whether you tolerate caffeine well or experience palpitations even with small quantities often depends on your genes. A specific gene plays a key role in determining whether you’re a ‘fast metaboliser’ or a ‘slow metaboliser’.
- Fast metabolisers feel the effects for a shorter time and can usually tolerate larger quantities.
- Slow metabolisers often react more sensitively and may still notice the effects of caffeine consumed in the afternoon while they're sleeping.
Age also plays a role: younger adults generally metabolise caffeine more quickly whilst the process slows down with age, which is why some people only start to notice problems with afternoon or bedtime coffee later in life.
07
Caffeine in sport: effects, dosage and pain threshold
We know it’s one of the most thoroughly researched legal substances in sport, used by both amateur and elite athletes to boost alertness, endurance and training performance. Since its removal from the WADA Prohibited List in 2004, it’s been one of the most popular ergogenic aids worldwide.
Highest quantities used
Early studies tested caffeine doses of up to 13 mg per kilogram of body weight (e.g. Graham and Spriet, 1995). These very high quantities frequently led to side effects such as palpitations, nervousness or stomach problems and are now considered impractical. In most recent studies, effective doses range from 3–6 mg/kg body weight — which corresponds to approximately 210–420 mg of caffeine for a 70-kg person. Even lower quantities of 2–3 mg/kg can lead to performance improvements.
Why dose per kg of body weight?
The effect of caffeine depends on the relative quantity in the body, so an absolute dose of 200 mg has significantly stronger effects in a 50 kg person than in a 100 kg athlete. This is why, in sports research, the dosage is specified in mg per kg of body weight.
Why caffeine is so popular in sport
- Improved alertness and reaction speed — caffeine blocks adenosine receptors and reduces fatigue.
- Increased endurance performance — the release of adrenaline and a slight shift in energy metabolism make exercise feel subjectively easier.
- Increased strength and sprinting performance – moderate effects, particularly during interval training.
- Higher pain threshold — caffeine reduces the perceived effort and intensity of pain, letting you train for longer and harder.
- It’s also freely available and is no longer on the list of prohibited substances monitored by WADA.
Practical recommendations
- Take 3–6 mg/kg 30–60 min before training or competition.
- Low dose: 1–3 mg/kg for sensitive individuals — still effective, with fewer side effects.
- High dose: >9 mg/kg offers no additional benefit and only increases the risk of side effects.
Take it 60 min before exercise or split smaller doses across the competition day.
Dosage (mg/kg body weight) | Effect | Risks/side effects |
1–3 | You'll notice a subtle performance boost and reduced fatigue. | Very few side effects |
3–6 | You'll notice optimal performance improvement in endurance and strength. | In isolated cases: nervousness, sleep problems |
>9 | No additional benefit | Heart palpitations, stomach problems and restlessness |
08
Caffeine as a travel aid — how the pros use it
Use it after westbound flights (Europe → USA) on the morning of arrival to reset your internal clock more quickly. Never take it on an empty stomach and never within 8–10 h of your planned bedtime.
Anna West, Sleep Performance Coach, uses caffeine as a timing tool in professional football — when players travel from Europe to the USA. This is exactly what everyone can expect at the 2026 World Cup, whether they’re following the matches on site or flying across the Atlantic themselves. The basic idea is this: caffeine isn’t simply a stimulant you drink — it’s a lever for your circadian rhythm that must be used judiciously.
This is well supported by scientific evidence: a dose of 3 mg/kg body weight, taken three hours before the natural waking phase, can shift the body’s internal clock by up to 40 minutes (Burke et al. 2015). For a person weighing 75 kg, this corresponds to approximately 225 mg of caffeine — roughly two espressos.
The five rules for travellers and World Cup fans
- Never drink iton an empty stomach: caffeine can trigger a strong insulin response and the brief energy boost often ends with a significant crash, so have breakfast first then enjoy your caffeine.
- Avoid caffeinewithin 8–10 h of your planned bedtime — its half-life is roughly 5–7 h — so if you plan to sleep at 11.00 pm, finish your last cup between 1.00 pm and 3.00 pm.
- On westbound flights (Europe → USA), consume caffeine specifically on the morning of arrival: avoid caffeine on the plane; wait until you reach your destination. This helps you stay more alert during the day and supports your body clock in adjusting more quickly. Consuming caffeine on the plane, when your body should actually be sleeping, can exacerbate jet lag.
- As a rough guide, aim for around 3 mg of caffeine per kg of body weight; for a 70 kg person that’s roughly 200–210 mg — about one large filter coffee or two espressos.
- In a sporting context, consume it 30–60 min before exercise to gain a 5–10% performance boost.
For further details on how elite teams use sleep to enhance performance, including the World Cup travel playbook, see our related articles; we also explore the connection between sport and sleep in greater depth.
09
Caffeine-free alternatives and everyday tips
Sometimes you’ll want to enjoy the taste and ritual of a hot drink without the stimulating effect of caffeine. This can be particularly helpful if you’re sensitive to caffeine, have trouble sleeping or want to cut down on your intake.
Three caffeine-free alternatives
- Herbal teas / ginger teas — peppermint, camomile or rooibos are naturally caffeine-free, have a pleasant flavour and may help you unwind.
- Grain coffee – made from barley, rye or chicory, it offers a coffee-like flavour without the caffeine.
- Dark chocolate — whilst it contains a small quantity of caffeine, it’s significantly less than in coffee or black tea. It also provides theobromine, which has a gentler stimulating effect and can lift your mood at the same time.
Five everyday tips for mindful caffeine consumption
- Plan caffeine-free periods — avoid caffeinated drinks for 6–8 h before bed to improve your sleep quality.
- Reduce your intake slowly to avoid withdrawal symptoms such as headaches.
- Watch out for hidden sources of caffeine — cola, energy drinks, chocolate and certain medicines may also contain caffeine.
- Vary your choices — replace every other cup of coffee or black tea with a caffeine-free alternative.
Enjoy mindfully — instead of automatically reaching for the next cup, ask yourself whether you really need to wake up — or whether a glass of water or a short walk will do the trick.
FAQ: The most frequently asked questions about caffeine
It blocks the sleep-inducing hormone adenosine in the brain, so you feel more alert and focused.
A typical cup of filter coffee contains around 60–100 mg of caffeine, while black tea contains roughly 30–60 mg.
The effect usually sets in after 15–30 min and can last for 3–7 h, depending on the individual.
Yes, too much caffeine can cause nervousness, sleep disturbances, a racing heart or stomach problems.
Yes, mild tolerance can develop and withdrawal symptoms such as headaches or tiredness may occur.
In moderate quantities it can boost stamina, concentration and short-term performance.
Yes, particularly when you drink it in the afternoon or evening, it can make falling asleep significantly harder.
Further items
Sources and Studies
Sport and Performance (Original sources)
- Guest, N. S., VanDusseldorp, T. A., Nelson, M. T., Grgic, J., Schoenfeld, B. J., Jenkins, N. D. M., Arent, S. M., Antonio, J. and Stout, J. R. (2021). International Society of Sports Nutrition Position Stand: Caffeine and Exercise Performance. Sports Medicine, 51, 1–43. https://doi.org/10.1007/s40279-018-0939-8
- Haca-Bender, P., Woźniak, E., Kasielski, M. and Pietras, T. (2024). The effect of caffeine on the physiological and performance parameters of combat sports athletes: a systematic review. Nutrients, 16(24), 4257. https://doi.org/10.3390/nu16244257
Safety and guidelines
- European Food Safety Authority (EFSA), Panel on Dietetic Products, Nutrition and Allergies (NDA). (2015). Scientific opinion on the safety of caffeine. EFSA Journal, 13(5), 4102. https://doi.org/10.2903/j.efsa.2015.4102
- Institute for Scientific Information on Coffee (ISIC). (n.d.). Coffee and IARC: What are the facts. Coffee and Health. https://www.coffeeandhealth.org/health/media-content/information-campaign/coffee-and-iarc-what-are-the-facts
Sleep and caffeine
- Drake, C., Roehrs, T., Shambroom, J. and Roth, T. (2013). Effects of caffeine on sleep when consumed 0, 3 or 6 hours before bedtime. Journal of Clinical Sleep Medicine, 9(11), 1195–1200. https://pubmed.ncbi.nlm.nih.gov/24235903/
- Burke, T. M. (2015). Caffeine delays the circadian rhythm and affects sleep timing. Science Translational Medicine, 7(285), 285ra61. https://doi.org/10.1126/scitranslmed.aac5125
- Lovato, N. and Lack, L. (2014). The effects of caffeine on sleep. PMCID: PMC4039055. National Institutes of Health. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4039055/
New, recent sources (2025–2026)
- Chen, Y.-S., Liu, X., Zhang, L., et al. (2026). Caffeine consumption and risk of dementia: A prospective cohort study of 131,821 participants over 43 years. JAMA. https://jamanetwork.com/journals/jama/fullarticle/caffeine-dementia-2026
- Hachenberger, J., Li, Y.-M., Realo, A. and Lemola, S. (2025). The association of caffeine consumption with positive affect but not with negative affect changes throughout the day. Scientific Reports, 15, 28471. https://doi.org/10.1038/s41598-025-14317-0
- Mayo Clinic. (30/01/2025). Coffee and health: What does the research say? Mayo Clinic. https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/expert-answers/coffee-and-health/faq-20058339