top of page

What is Caffeine? Is it good for your health?


Posted: 17/09/2019

Updated: 17/09/2019

Who loves their cup of coffee in the morning? Or afternoon? Or even after your evening meal? 


Caffeine, found in many beverages such as coffee, tea, energy drinks and even in food products, helps many of us stay awake throughout the day.


Approximately 81% of the US population consumes caffeine on a regular basis.

So what is all this fuss about? In this article, we will discuss caffeine, how it is consumed around the world, how it works in our body, its benefits and side effects!

what is Caffeine?


Caffeine occurs naturally in coffee beans, tea leaves, cocoa beans, kola nuts and is added to many foods and beverages such as caffeinated soda and energy drinks.


Caffeine stimulates the central nervous system (CNS) and in moderation results in alertness, raising energy levels and heart rate. Thus, it is the most commonly consumed psychoactive substance worldwide.

How is caffeine consumed in the world?

How is caffeine consumed?
Image by Joanna Kosinska

Here's an overall list (there are huge variations between the countries) of what are the leading caffeinated drinks around the continents:

  • Africa: Tea (black) and carbonated soda (non-cola-type)

  • Asia and the Pacific: Tea (black, green and other) and carbonated soda (cola-type)

  • Europe: Coffee and carbonated soft drinks (cola-type) Coffee drinkers: Netherlands, Finland, Sweden Tea drinkers: Ireland, Turkey, UK, Latvia

  • Latin America and Caribbean: Carbonated soda (mostly cola-type) and coffee (mostly fresh-brewed)

  • North America: Coffee (Fresh-brewed) and carbonated sodas



In general, up to 400 mg caffeine/day is considered to be safe for most healthy adults which is equivalent to:

  • 5 shots of espresso

  • 1 Starbucks Venti brewed coffee

  • 2.5 x 500 mL Monster Energy Drinks

  • 5 x 250 mL Red Bulls

  • 12 x 350 mL Cokes

Other recommendations in other parts of the world

  • Indonesia and New Zealand: <250-300 mg/day for pregnant women

  • Albania, Belgium, Denmark, Ireland, Latvia and Romania: <200 - 300 mg/day for pregnant and lactating women

  • Canada and America: <300 mg/day for pregnant and breastfeeding women

  • New Zealand: <300 mg/day for older people due to bone health

  • Portugal: <300 mg/day for healthy people

  • Netherlands: recommends daily consumption of 3 cups of green/black tea

The guidelines cannot be applied to everyone as people can have different sensitivities or reactions to caffeine based on age, body weight, medical history and tolerance.


As children and adolescents are smaller than adults, a lower amount can lead to side effects such as headaches, insomnia, jitteriness and increased blood pressure.


Another concern may not be the caffeine content but rather the empty calories and high sugar content that often comes along with the caffeinated drink. For instance, a single can of coca-cola alone provides 140 kcal and 39 g of sugar. A Starbucks grande caramel frappuccino coffee has a whopping 420 kcal and 66 g of sugar.


The European Food Safety Authority (EFSA) states that 3 mg of caffeine per kg of body weight is safe for children and adolescents.

  • US: no guidelines

  • Canada: <2.5 mg/kg body weight day (equivalent to 1 can of coke)

Caffeine sensitivity, caffeine in pregnancy and lactation

Those who are sensitive to caffeine and pregnant/nursing women may want to limit their caffeine consumption to avoid possible side effects.

Some people are more sensitive to caffeine and even in small quantities may result in unwanted side effects. Those who do not consume caffeine regularly tend to be more sensitive.

Some evidence suggests that higher caffeine intake may be associated with a higher risk of pregnancy loss and lower birth weight baby. However, a review found that moderate to high caffeine intake does not increase the risk of congenital malformations, miscarriage or growth retardation.


Small amounts of caffeine can be passed through breast milk and large amounts can make babies restless so it has been recommended to limit caffeine intake to below 200 mg/day. 

So how much do we consume?

how much do we consume

According to the European Food Safety Authority (EFSA), it has been revealed that caffeine consumption increases with age and the highest caffeine intake was seen in the elderly (75+ years).

Possible benefits


It may be beneficial to consume caffeine in moderate amounts as it has been linked to a reduced risk of several chronic diseases.


Cardiovascular Health

High doses of caffeine can temporarily increase your heart rate and blood pressure which tends to fade away after time. However, the link between caffeine and heart conditions remains controversial and it has been suggested that moderate consumption is not linked to cardiovascular disease (CVD) in the long term. In fact, some studies have suggested caffeine to be protective against heart disease.

Type 2 Diabetes

Participants who increased their coffee consumption by more than one cup per day had a 1% lower risk of developing type 2 diabetes. Those who reduced their consumption by more than one cup had a 17% higher chance of developing type 2 diabetes. Note that only coffee was studied and not caffeine in general.


Interestingly, decaffeinated coffee was associated with a reduced risk of type 2 diabetes suggesting that there are possible other beneficial components in coffee that may be linked to this.

Cognitive Health

People who drink coffee regularly have a reduced risk of developing Alzheimer's disease and dementia.


In this observational study, it has found that adults aged > 65 who consumed an average of 261 mg caffeine per day compared to those who consumed an average of 64 mg per day reported fewer dementia symptoms. However, results may be due to antioxidants or other nutrients from caffeinated drinks rather than caffeine alone.

Studies have demonstrated that caffeine increases memory and reasoning in sleep-deprived individuals.


Additionally, those who consumed at least three cups of coffee per day (around 300 mg caffeine) is linked to a slower cognitive decline in women especially at higher ages.

possible side effects

Side effects

Some people may be more sensitive to caffeine and this could cause unpleasant side effects such as:

  • Migraine headache

  • Insomnia

  • Nervousness

  • Irritability

  • Restlessness

  • Stomach upset

  • Fast heartbeat

  • Muscle tremors

Overdose of caffeine or also known as "caffeinism" typically reaching a dose of 1 - 1.5 g per day can lead to:

Caffeine overdose.png

Death is possible especially when taking caffeine products in very concentrated or pure forms.


Caffeine powder can provide approximately 200 mg per 1/32 tsp and caffeine pills average between 100 to 200 mg per tablet.


It can be very easy to overdo it and hence, it should be used in moderation. There have been cases of accidental overdosages on caffeine powder over the past decade.


Regular high consumption can lead to caffeine withdrawal as well:

  • Headache

  • Fatigue

  • Anxiety

  • Irritability

  • Drowsiness

It is recommended that individuals gradually reduce their consumption to avoid symptoms appearing.

Amount of caffeine in drinks

amount of caffeine

Please note that data was gathered in 2019 so the caffeine content in the following products may since been updated.

*Amount based on 400 mg/day


Starbucks nutritional information here. Costa and Caffe Nero have not disclosed the amount of caffeine in their drinks on their website. Values from Caffeine Informer. However, Costa drinks contain the highest caffeine content amongst all brands.


Concentrations in coffee beverages depend on the manufacturing process, the type of coffee beans used, and the type of preparation (e.g. drip coffee, espresso).

List of various brands for coffees, teas, soft drinks and energy drinks


The levels found in cocoa-based beverages depend on the amount and type of cocoa present in different brands.

Amount of caffeine in food

Amount of caffeine in other products

Caffeine is a common ingredient in medications such as pain relievers to treat headaches and migraines, weight loss supplements and premenstrual syndrome (PMS) pills



Whilst I am enjoying my coffee writing this article, increasing evidence suggests that caffeine intake can be beneficial to health when consumed within the safety levels.


However, it is not to say you should start having caffeinated beverages if you are not a big fan of them.

So feel free and enjoy your day with a cup of tea or coffee!

  • References
    Irritable bowel syndrome [Online] Available at: [Accessed: 22 June 2018]. Saha, L. (2014). Irritable bowel syndrome: Pathogenesis, diagnosis, treatment, and evidence-based medicine. World Journal of Gastroenterology, 20(22), p.6759. D. Cashman, M., K. Martin, D., Dhillon, S. and R. Puli, S. (2016). Irritable Bowel Syndrome: A Clinical Review. Current Rheumatology Reviews, 12(1), pp.13-26. Guidelines--Rome III Diagnostic Criteria for Functional Gastrointestinal Disorders. (2006). Journal of Gastrointestinal and Liver Diseases, 15(3), pp.307-12. Drossman, D. (2016). Functional Gastrointestinal Disorders: History, Pathophysiology, Clinical Features, and Rome IV. Gastroenterology, 150(6), pp.1262-1279.e2. Ikechi, R., Fischer, B., DeSipio, J. and Phadtare, S. (2017). Irritable Bowel Syndrome: Clinical Manifestations, Dietary Influences, and Management. Healthcare, 5(2), p.21. Enck, P., Aziz, Q., Barbara, G., Farmer, A., Fukudo, S., Mayer, E., Niesler, B., Quigley, E., Rajilić-Stojanović, M., Schemann, M., Schwille-Kiuntke, J., Simren, M., Zipfel, S. and Spiller, R. (2016). Irritable bowel syndrome. Nature Reviews Disease Primers, 2, p.16014. Chey, W., Kurlander, J. and Eswaran, S. (2015). Irritable Bowel Syndrome. JAMA, 313(9), p.949. Hungin, A., Chang, L., Locke, G., Dennis, E. and Barghout, V. (2005). Irritable bowel syndrome in the United States: prevalence, symptom patterns and impact. Alimentary Pharmacology and Therapeutics, 21(11), pp.1365-1375. Gibson, P., Varney, J., Malakar, S. and Muir, J. (2015). Food Components and Irritable Bowel Syndrome. Gastroenterology, 148(6), pp.1158-1174.e4. Card, T., Canavan, C. and West, J. (2014). The epidemiology of irritable bowel syndrome. Clinical Epidemiology, p.71. Occhipinti, K. and Smith, J. (2012). Irritable Bowel Syndrome: A Review and Update. Clinics in Colon and Rectal Surgery, 25(01), pp.046-052. Chey, W., Kurlander, J. and Eswaran, S. (2015). Irritable Bowel Syndrome. JAMA, 313(9), p.949. Zhou, Q. and Verne, G. (2011). New insights into visceral hypersensitivity—clinical implications in IBS. Nature Reviews Gastroenterology & Hepatology, 8(6), pp.349-355. Ghoshal, U., Kumar, S., Mehrotra, M., Lakshmi, C. and Misra, A. (2010). Frequency of Small Intestinal Bacterial Overgrowth in Patients with Irritable Bowel Syndrome and Chronic Non-Specific Diarrhea. Journal of Neurogastroenterology and Motility, 16(1), pp.40-46. Ghoshal, U., Shukla, R. and Ghoshal, U. (2017). Small Intestinal Bacterial Overgrowth and Irritable Bowel Syndrome: A Bridge between Functional Organic Dichotomy. Gut and Liver, 11(2), pp.196-208. Ghoshal, U. (2014). Irritable bowel syndrome and small intestinal bacterial overgrowth: Meaningful association or unnecessary hype. World Journal of Gastroenterology, 20(10), p.2482. Marshall, J., Thabane, M., Garg, A., Clark, W., Moayyedi, P. and Collins, S. (2010). Eight year prognosis of postinfectious irritable bowel syndrome following waterborne bacterial dysentery. Gut, 59(5), pp.605-611. Marshall, J., Thabane, M., Garg, A., Clark, W., Salvadori, M. and Collins, S. (2006). Incidence and Epidemiology of Irritable Bowel Syndrome After a Large Waterborne Outbreak of Bacterial Dysentery. Gastroenterology, 131(2), pp.445-450. Spiller, R. and Campbell, E. (2006). Post-infectious irritable bowel syndrome. Current Opinion in Gastroenterology, 22(1), pp.13-17. Ericsson, C., Hatz, C. and DuPont, A. (2008). Postinfectious Irritable Bowel Syndrome. Clinical Infectious Diseases, 46(4), pp.594-599. Grenham, S., Clarke, G., Cryan, J. and Dinan, T. (2011). Brain?Gut?Microbe Communication in Health and Disease. Frontiers in Physiology, 2. The Brain-Gut Connection [Online] Available at: [Accessed: 24 June 2018]. Folks, D. (2004). The interface of psychiatry and irritable bowel syndrome. Current Psychiatry Reports, 6(3), pp.210-215. Fichna, J. and Storr, M. (2012). Brain-Gut Interactions in IBS. Frontiers in Pharmacology, 3. El-Salhy, M. and Gundersen, D. (2015). Diet in irritable bowel syndrome. Nutrition Journal, 14(1). Irritable Bowel Syndrome - National Library of Medicine - PubMed Health [Online] Available at: [Accessed: 24 June 2018]. Folks, D. (2004). The interface of psychiatry and irritable bowel syndrome. Current Psychiatry Reports, 6(3), pp.210-215. Ikechi, R., Fischer, B., DeSipio, J. and Phadtare, S. (2017). Irritable Bowel Syndrome: Clinical Manifestations, Dietary Influences, and Management. Healthcare, 5(2), p.21. Rao, S., Yu, S. and Fedewa, A. (2015). Systematic review: dietary fibre and FODMAP-restricted diet in the management of constipation and irritable bowel syndrome. Alimentary Pharmacology & Therapeutics, 41(12), pp.1256-1270. Moayyedi, P., Quigley, E., Lacy, B., Lembo, A., Saito, Y., Schiller, L., Soffer, E., Spiegel, B. and Ford, A. (2014). The Effect of Fiber Supplementation on Irritable Bowel Syndrome: A Systematic Review and Meta-analysis. The American Journal of Gastroenterology, 109(9), pp.1367-1374. FRANCIS, C. (1994). Bran and irritable bowel syndrome: time for reappraisal. The Lancet, 344(8914), pp.39-40. Vazquez–Roque, M., Camilleri, M., Smyrk, T., Murray, J., Marietta, E., O'Neill, J., Carlson, P., Lamsam, J., Janzow, D., Eckert, D., Burton, D. and Zinsmeister, A. (2013). A Controlled Trial of Gluten-Free Diet in Patients With Irritable Bowel Syndrome-Diarrhea: Effects on Bowel Frequency and Intestinal Function. Gastroenterology, 144(5), pp.903-911.e3. Ford, A., Quigley, E., Lacy, B., Lembo, A., Saito, Y., Schiller, L., Soffer, E., Spiegel, B. and Moayyedi, P. (2014). Efficacy of Prebiotics, Probiotics and Synbiotics in Irritable Bowel Syndrome and Chronic Idiopathic Constipation: Systematic Review and Meta-analysis. The American Journal of Gastroenterology, 109(10), pp.1547-1561. Basturk, A., Artan, R. and Yilmaz, A. (2016). Efficacy of synbiotic, probiotic, and prebiotic treatments for irritable bowel syndrome in children: A randomized controlled trial. The Turkish Journal of Gastroenterology, 27(5), pp.439-443. Zhang, Y., Li, L., Guo, C., Mu, D., Feng, B., Zuo, X. and Li, Y. (2016). Effects of probiotic type, dose and treatment duration on irritable bowel syndrome diagnosed by Rome III criteria: a meta-analysis. BMC Gastroenterology, 16(1). Guandalini, S., Magazzù, G., Chiaro, A., La Balestra, V., Di Nardo, G., Gopalan, S., Sibal, A., Romano, C., Canani, R., Lionetti, P. and Setty, M. (2010). VSL#3 Improves Symptoms in Children With Irritable Bowel Syndrome: A Multicenter, Randomized, Placebo-Controlled, Double-Blind, Crossover Study. Journal of Pediatric Gastroenterology and Nutrition, 51(1), pp.24-30. Paineau, D., Payen, F., Panserieu, S., Coulombier, G., Sobaszek, A., Lartigau, I., Brabet, M., Galmiche, J., Tripodi, D., Sacher-Huvelin, S., Chapalain, V., Zourabichvili, O., Respondek, F., Wagner, A. and Bornet, F. (2007). The effects of regular consumption of short-chain fructo-oligosaccharides on digestive comfort of subjects with minor functional bowel disorders. British Journal of Nutrition, 99(02). Khanna, R., MacDonald, J. and Levesque, B. (2013). Peppermint Oil for the Treatment of Irritable Bowel Syndrome. Journal of Clinical Gastroenterology, p.1. Peppermint Oil for IBS: Does it Work? [Online] Available at: [Accessed: 24 June 2018]. Grigoleit, H. and Grigoleit, P. (2005). Peppermint oil in irritable bowel syndrome. Phytomedicine, 12(8), pp.601-606. Khanna, R., MacDonald, J. and Levesque, B. (2013). Peppermint Oil for the Treatment of Irritable Bowel Syndrome. Journal of Clinical Gastroenterology, p.1. IBS Diet: What to Do and What to Avoid [Online] Available at: [Accessed: 24 June 2018]. Johannesson, E., Simrén, M., Strid, H., Bajor, A. and Sadik, R. (2011). Physical Activity Improves Symptoms in Irritable Bowel Syndrome: A Randomized Controlled Trial. The American Journal of Gastroenterology, 106(5), pp.915-922.
bottom of page