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Whatever form it comes in, caffeine is a go-to for many of us seeking an
energy boost. Find out how caffeine works and whether or not it’s good for you.
Summary
1The effects of caffeine
Research shows that the levels of adenosine – the hormone that controls feelings of tiredness – can build up in your central nervous system...
2The possible benefits of caffeine
We know, so far, that caffeine can give your energy levels a much-needed boost, but what else can it do for you? Some of the possible benefits...
3The potential side effects of caffeine
Dependency - Caffeine is a drug, so you can become dependent on it. If you don’t give in to your body's caffeine cravings, research highlights...
A morning cup of Joe, an afternoon cuppa, a night shift energy drink… all these things have one
thing in common – caffeine!
Caffeine features pretty heavily in most of our everyday lives, but how much do you know about
what it is, how it affects you and how much is safe to have?
We’re taking a deep dive into the world of caffeine to look at whether it’s good for you, bad for
you or a little bit of both.
What is caffeine?
Caffeine is the world’s most popular drug. Yep, you read that right.1
It’s a naturally occurring chemical compound found in the fruit, leaves and beans of coffee, cacao and guarana plants. When extracted in its pure form, it’s a white, bitter-tasting powder.1
In our day-to-day lives, it can be found in all sorts of drinks and food items, including coffee, tea, fizzy drinks, energy drinks and chocolate. It can also be found in energy supplements and some medications, such as cold and flu remedies.1
The effects of caffeine
Research shows that the levels of adenosine – the hormone that controls feelings of tiredness – can build up in your central nervous system throughout the day, helping you to fall into a deep sleep at night.2
When you consume something that has caffeine in it, your liver breaks it down to release
stimulating chemicals which are quickly absorbed into your bloodstream.2,3
It’s thought that caffeine blocks the effects of adenosine by binding to adenosine receptors in
the brain. According to some studies, this not only lowers adenosine levels but it can also affect
the levels of other important hormones that help control sleep. In addition to this, caffeine may
also increase the activity of your central nervous system and stimulate your brain, thus
increasing your energy levels and alertness.2,3
These stimulatory effects may begin 15 to 30 minutes after consuming caffeine, and can last
several hours.3
How long it takes for a caffeine buzz to wear off may depend on a few factors such as your age,
body weight and if you smoke cigarettes. Generally, it takes around four hours for just half of a
dose of caffeine to be metabolised (processed) by the body.3
The possible benefits of caffeine
We know, so far, that caffeine can give your energy levels a much-needed boost, but what else
can it do for you? Here are some of the possible benefits caffeine may have.
These benefits aren’t yet backed by robust scientific evidence as research into all these
potential effects is in its infancy. Much more carefully designed studies with larger
human clinical trials are needed to conclude these findings.
A research review has shown that caffeine can have a positive effect on physical performance
in both regular people and professional athletes.4 So, a hit of caffeine before a workout might
just help you reach your personal best in the gym or on the tarmac.
There’s also evidence showing that caffeine can have a pain-blocking effect, which may aid
recovery from delayed-onset muscle soreness (DOMS).5,6
According to a meta-analysis of the effects of coffee on depression and depressive symptoms,
those who consumed higher levels of caffeine were at a lower risk of depression than people
who consumed less or no caffeine.7
More research is needed, but a recent study also suggests that caffeine may have a significant
positive effect on short- and long-term memory, and may help with learning too.8
Some studies in rats and humans found that ingesting coffee every day may be linked to a
slower decline in cognitive function and attention, and could also lower your chance of
developing Alzheimer’s disease.9
More studies are needed to know for sure, but another study showed that caffeine could slightly
reduce the risk of developing dementia too, but in women only. However, results are mixed at
the moment and further high-quality research is required.10
Emerging research has found that coffee may reduce your risk of liver damage, including
scarring and cirrhosis, and may also lower your chance of developing a type of liver cancer
called hepatocellular carcinoma.11,12,13
There’s also some evidence that suggests that coffee can also slow the progression of liver
disease and even reduce the chance of premature death.11
One recent UK-based study found that drinking six cups of tea or three cups of coffee a day
could reduce your risk of developing gout by as much as 23% and 40%, respectively.14 However,
more research is needed to confirm this.
Find out more about foods that are linked to gout and living with gout.
Research has found that coffee can positively impact your gut microbiome due to its prebiotic
properties, fostering the growth and activity of good gut bacteria. Drinking coffee regularly may
also lower harmful species of microbes in the gut.14,15
The potential side effects of caffeine
Despite the many benefits of caffeine, it can have some downsides.
1. More anxiety
A meta-analysis from this year revealed levels of cortisol, commonly known as the stress hormone, may be significantly increased by caffeine, especially if the dosage is greater than
400mg. So, while caffeine can boost energy levels, it may also make you feel jittery and elevate
feelings of anxiety.16
Consuming too much caffeine can also disrupt your sleep and speed up your heartbeat, which
can make you feel more anxious.17
Want to learn more? Visit our article, ‘Does caffeine cause anxiety?’.
2. Dependency
When all is said and done, caffeine is a drug, so you can become dependent on it.
If you don’t give in to your body's caffeine cravings, recent research highlights that it can
potentially cause withdrawal symptoms, such as fatigue, low mood, headaches, brain fog,
irritability and difficulty concentrating.18
3. Digestive issues
Due to its laxative effect, many people rely on their morning coffee to keep things regular.
But you need to be careful not to drink too much, as some research reveals that coffee can
increase your risk of digestive issues, including poor digestion, nausea, heartburn, burping and
wind.19
4. Increased blood pressure
Drinking more than four cups of coffee a day might increase your blood pressure.
If you’re worried, cutting down or choosing decaf alternatives can keep your blood pressure in check.20,21
What’s the acceptable daily limit of caffeine?
Healthy adults should limit their caffeine intake to 400mg per day. It’s important to know that
some people are more sensitive to the effects of caffeine than others, so you may need to limit
your intake to less than this.22
Keep in mind that although ‘decaffeinated’ versions of most drinks are available, most still
contain small amounts of caffeine.22
Use this guide to help you keep track of your caffeine intake:23
- mug of instant coffee – 100mg
- mug of filter coffee – 140mg
- mug of tea – 75mg
- can of cola – 40mg
- 250mL can of energy drink – 80mg
- 50g of plain dark chocolate – less than 25mg
- 50g of plain milk chocolate – less than 10mg
Who should avoid caffeine?
Caffeine is safe for most adults to have in moderation.
If you’re pregnant or breastfeeding, it’s advised by the NHS that you limit your caffeine intake to
no more than 200mg a day maximum, as regularly drinking more than this may increase your
risk of pregnancy complications. However, it’s still generally advised to avoid caffeine
completely during pregnancy.24,25
If you’re worried about how caffeine may interact with any medications or affect a medical
condition, we recommend speaking to your GP for personalised advice.
The final say
Whether you’re just getting into having a coffee in the morning before work or relying on energy
drinks to get you through a night shift, remember that moderation is key.
Aim to have no more than 400mg a day and we’re sure you’ll be able to keep your caffeine habit
a healthy one.26
The advice in this article is for information only and shouldn’t replace medical care. Please
check with your GP or healthcare professional before trying any supplements, treatments or
remedies. Food supplements must not be used as a substitute for a varied and balanced diet
and a healthy lifestyle.
- European Food Safety Authority. Caffeine [Internet]. [cited 2024 Apr 11]. Available from: https://www.efsa.europa.eu/sites/default/files/corporate_publications/files/efsaexplainscaffei ne150527.pdf.
- Guest NS, et al. International society of sports nutrition position stand: Caffeine and exercise performance. J Int Soc Sports Nutr. 2021;18(1):1. DOI: https://doi.org/10.1186/s12970-020-00383-4.
- Muljadi JA, et al. Effect of caffeine on delayed-onset muscle soreness: A meta-analysis of RCT. Bull Natl Res Cent. 2021;45(1):197. DOI: https://doi.org/10.1186/s42269-021- 00660-5
- Hurley CF, et al. The effect of caffeine ingestion on delayed onset muscle soreness. The J Strength Cond Res. 2021;27(11):3101–09. DOI: https://doi.org/10.1519/JSC.0b013e3182a99477.
- ncausa.org. Coffee & Mental Health [Internet]. [cited 2024 Apr 11]. Available from: https://www.ncausa.org/Portals/56/PDFs/Communication/20200504_Leviton_white_paper_fi nal.pdf.
- Fiani B, et al. The neurophysiology of caffeine as a central nervous system stimulant and the resultant effects on cognitive function. Cureus. 2021;13(5):e15032. DOI: https://doi.org/10.7759/cureus.15032.
- Gardener SL, et al. Higher coffee consumption is associated with slower cognitive decline and less cerebral aβ-amyloid accumulation over 126 months: Data from the Australian imaging, biomarkers, and lifestyle study. Front Aging Neurosci. 2021;13. DOI: https://doi.org/10.3389/fnagi.2021.744872.
- Alzheimer’s Society. Caffeine and the risk of dementia [Internet]. [cited 2024 Apr 11]. Available from: https://www.alzheimers.org.uk/about-dementia/managing-the-risk-of- dementia/possible-risks-of-dementia/caffeine.
- British Liver Trust. Coffee and your liver FAQs [Internet]. [cited 2024 Apr 11]. Available from: https://britishlivertrust.org.uk/information-and-support/living-with-a-liver- condition/coffee/.
- Dranoff JA. Coffee Consumption and Prevention of Cirrhosis: In Support of the Caffeine Hypothesis. Gene expression [Internet]. 2018 Mar 21 [cited 2024 Jun 14];18(1):1–3. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5885142/
- Arauz J, Zarco N, Hernández-Aquino E, Galicia-Moreno M, Favari L, Segovia J, et al. Coffee consumption prevents fibrosis in a rat model that mimics secondary biliary cirrhosis in humans. Nutrition research [Internet]. 2017 Apr 1 [cited 2024 Jun 14];40:65–74. Available from: Evans J, Richards JR, Battisti AS. Caffeine [Internet]. Nih.gov. StatPearls Publishing; 2024 [cited 2024 Jun 14]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK519490/
- Reichert CF, et al. Adenosine, caffeine, and sleep-wake regulation: State of the science and perspectives. J Sleep Res. 2022;31(4):e13597. DOI: https://doi.org/10.1111/jsr.13597.
- https://www.sciencedirect.com/science/article/abs/pii/S0271531716306376?via%3Dihub
- Huangda Guo, et al. Dose–response relationships of tea and coffee consumption with gout: a prospective cohort study in the UK Biobank. Rheumatology. 2023;62(9):3043–3050. DOI: https://doi.org/10.1093/rheumatology/kead019.
- Nehlig A. Effects of Coffee on the Gastro-Intestinal Tract: A Narrative Review and Literature Update. Nutrients [Internet]. 2022 Jan 17 [cited 2024 Jun 14];14(2):399–9. Available from: https://www.mdpi.com/2072-6643/14/2/399
- Canadian Digestive Health Foundation. Is coffee bad for digestion? [Internet]. [cited 2024 Apr 11]. Available from: https://cdhf.ca/en/is-coffee-bad-for-digestion/.
- Liu C, et al. Caffeine intake and anxiety: a meta-analysis. Front Psychol. 2024;15:1270246. DOI: https://doi.org/10.3389/fpsyg.2024.1270246.
- NHS. Self-help - Generalised anxiety disorder in adults [Internet]. [cited 2024 Apr 11]. Available from: https://www.nhs.uk/mental-health/conditions/generalised-anxiety- disorder/self-help/.
- Sajadi-Ernazarova KR, et al. Caffeine withdrawal. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 [cited 2024 Apr 11]. Available from: http://www.ncbi.nlm.nih.gov/books/NBK430790/
- Nehlig A. Effects of coffee on the gastro-intestinal tract: A narrative review and literature update. Nutrients. 2022;14(2):399. DOI: https://doi.org/10.3390/nu14020399.
- Lire Wachamo H. Review on Health Benefit and Risk of Coffee Consumption. Medicinal & Aromatic Plants. 2017;06(04).
- NHS. High blood pressure (hypertension) [Internet]. [cited 2024 Apr 11]. Available from: https://www.nhs.uk/conditions/high-blood-pressure-hypertension/prevention/.
- U.S. Food and Drug Administration. Spilling the beans: how much caffeine is too much? [Internet]. [cited 2024 Apr 11]. Available from: https://www.fda.gov/consumers/consumer- updates/spilling-beans-how-much-caffeine-too-much.
- NHS. Foods to avoid in pregnancy [Internet]. [cited 2024 Apr 11]. Available from: https://www.nhs.uk/pregnancy/keeping-well/foods-to-avoid/.
- James JE. Maternal caffeine consumption and pregnancy outcomes: a narrative review with implications for advice to mothers and mothers-to-be. BMJ evidence-based medicine [Internet]. 2020 Aug 25 [cited 2024 Jun 14];26(3):114–5. Available from: https://ebm.bmj.com/content/26/3/114
- Temple JL, Bernard C, Lipshultz SE, Czachor JD, Westphal JA, Mestre MA. The Safety of Ingested Caffeine: A Comprehensive Review. Frontiers in psychiatry [Internet]. 2017 May 26 [cited 2024 Jun 14];8. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5445139/
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