Millions of us can’t start the day without a cup of tea or coffee. In the UK, nearly 100 million cups of tea and 95 million cups of coffee are consumed daily, according to Bupa. This represents a substantial amount of caffeine in circulation.
But what exactly happens in the body when you consume it? Let’s explore.
How caffeine works
Caffeine is a natural stimulant found in approximately 60 plants, including coffee beans, tea leaves, and cacao, the key ingredient in chocolate. It stimulates the brain and central nervous system, keeping us alert and awake.
Caffeine achieves this by blocking adenosine, a chemical in the brain that naturally builds up over the day to induce sleepiness. This mechanism explains why a cup of coffee can provide an immediate boost during an afternoon slump.
The effects of caffeine typically peak within an hour but it can take several more hours for your body to process it. In the average adult, caffeine has a half-life of between four and six hours, which means that mid-afternoon coffee can still be keeping you awake at bedtime.
Are there any benefits of caffeine?
Caffeine is widely used as a pick-me-up and is known to:
Increase alertness: By blocking the actions of adenosine, a chemical that makes us feel sleepy, caffeine can help you feel alert and sharp.
Enhance mood: Caffeine stimulates the production of dopamine, the “feel-good” neurotransmitter.
Improve concentration: Some studies indicate caffeine can improve concentration and focus.
Longer-term benefits may include support for memory and cognitive function. Research suggests regular coffee consumption is associated with better performance in cognitive tests. Older adults who consume caffeine may have a lower risk of developing Alzheimer’s or other age-related memory conditions.
Moderate coffee intake may also contribute to improved mood and potentially lower the risk of depression due to increased dopamine activity.
What are the negative effects of caffeine?
While caffeine provides a useful boost, drinking too much can affect your heart, circulation, digestion, and other areas of health:
Increase your blood pressure
Caffeine and heart health are often discussed together, yet moderate intake – approximately four to five cups per day – is generally considered safe for heart function according to the British Heart Foundation.
However, caffeine can cause a temporary increase in blood pressure and a slightly elevated heart rate. People who are sensitive to caffeine may experience palpitations and may need to reduce their intake. WebMD notes that energy drinks, particularly in larger quantities, may increase the likelihood of abnormal heart rhythms and elevated blood pressure.
Increase urination and affect digestion
Caffeine has various effects on digestion and bladder function:
Diuretic effect: Caffeine can irritate the bladder, increasing the need to urinate. It’s important to bear this in mind if you have a UTI (urinary tract infection) or take medication for kidney function or high blood pressure.
Stomach acid production: Caffeine can increase stomach acid levels and contribute to heartburn and acid reflux.
Mild muscle stimulant: Caffeine stimulates the muscles in the wall of the digestive tract, which is why many people find their morning cuppa triggers a bowel movement. For people with IBS (irritable bowel syndrome) or a sensitive digestion, this stimulative effect can sometimes be too much.
Despite common beliefs, tea and coffee still contribute to daily fluid intake, as their dehydrating effect is minimal.
Trigger certain medical conditions
Caffeine may exacerbate symptoms in people with irritable bowel syndrome (IBS), leading to bloating, stomach cramps, or diarrhoea. It can also worsen anxiety, hyperactivity and insomnia.
Other potential short-term effects
Excessive caffeine intake may also:
Temporarily raise blood pressure.
Increase heart rate.
Cause jitteriness or anxiety.
Contribute to mild dehydration.
Everyone has their own personal tolerance level for caffeine, which can shift over a lifetime. If you start to feel anxious, shaky, or have stomach cramps after caffeine, it can be a sign that your intake is more than you can comfortably handle.
How much caffeine should you have in a day?
The suggested safe limit for caffeine intake varies:
Adults: Up to 400mg per day, which is approximately four to five cups of coffee.
Pregnant or breastfeeding: No more than 200mg per day.
Children: Roughly 3mg per kg of body weight.
Does caffeine affect everyone the same?
Responses to caffeine vary depending on your age, body weight, biological sex (women generally metabolise caffeine slower than men), genetics and habitual intake.
Our ability to process caffeine becomes less effective with age, and many women notice a difference in their tolerance level during pregnancy, perimenopause and menopause.
How much caffeine is in certain food and drinks?
Caffeine is present not only in coffee but also in tea, chocolate, fizzy drinks, and energy drinks. Typical caffeine content in common items is shown below:
Drink/food | Typical serving | Approx. caffeine content | % of adult daily intake |
|---|---|---|---|
Espresso | 60ml | 80mg | 20% |
Filter coffee | 200ml | 90mg | 22.5% |
Black tea | 220ml | 50mg | 12.5% |
Cola | 355ml | 40mg | 10% |
Energy drink | 250ml | 80mg | 20% |
Milk chocolate | 50g | 10mg | 4% |
Dark chocolate | 50g | 25mg | 6.25% |
How does caffeine affect your sleep?
Caffeine opposes the activity of melatonin, the hormone that regulates sleep. Too much caffeine can affect your ability to fall asleep and stay asleep and may affect the quality of your sleep.
The effects of caffeine may persist for up to 9.5 hours, meaning an afternoon coffee can easily still affect you at bedtime.
Is caffeine OK when you’re pregnant?
Pregnant individuals or those planning a pregnancy should monitor their caffeine intake. Too much caffeine can affect fetal development, particularly in early stages of pregnancy as the foetus processes caffeine more slowly.
While complete avoidance is unnecessary, it is advisable to limit intake to less than 200mg per day – equivalent to around two cups of coffee. Consult a healthcare professional for guidance if unsure.
How can you cut back on caffeine?
For those considering reducing caffeine, the following strategies can help:
Gradual reduction: Avoid quitting abruptly to prevent headaches, fatigue or irritability.
Timing: Limit caffeinated beverages in the afternoon or evening, or opt for decaf.
Check other sources: Be aware of chocolate, fizzy drinks and certain medications.
Hydration: Slowly replace caffeinated drinks with water or herbal teas.
Caffeine is generally safe in moderation. However, everyone tolerates it differently. If you’re noticing sleep disruption, anxiety, digestive symptoms, or palpitations, it may be time to reduce your intake.
FAQs
How long does caffeine stay in your system?
Peak levels occur about an hour after consumption, but you’ll still have caffeine in your system four to six hours later, potentially up to 9.5 hours.
Can you become addicted to caffeine?
Regular consumption can lead to habituation. Cutting down caffeine may cause temporary withdrawal symptoms like headache and irritability, though this is not considered a serious addiction.
What are the symptoms of caffeine withdrawal?
You may experience headaches, fatigue, irritability or difficulty concentrating if you suddenly cut back on caffeine, but these symptoms typically resolve as your body adjusts.
Does decaf coffee still contain caffeine?
Yes, decaf coffee is not completely caffeine-free. A 200ml cup contains roughly 7mg, compared to about 100mg in a regular cup.
Can caffeine affect anxiety or panic attacks?
Caffeine may exacerbate jitteriness or anxiety, particularly in those with pre-existing anxiety or panic disorders. Some individuals may experience a recognised “caffeine-induced anxiety” reaction.
Is caffeine affecting my skin or causing breakouts?
Caffeine does not directly cause acne, but disruption to sleep or increased stress on the body could indirectly affect the skin. Moderate intake and careful timing may help reduce these effects.
Sources
https://www.bupa.co.uk/newsroom/ourviews/how-caffeine-affects-body
https://www.webmd.com/diet/how-caffeine-affects-your-body
