Just what is caffeine and what is it doing to your health, both positively and negatively? Let’s take a look at the facts about caffeine.
On average, three-quarters of Aussies enjoy at least one cup of coffee per day, with 28% having three or more1. The love of coffee is strong in Australia – it’s a social ritual and comes with an energy boost in the form of caffeine.
What is caffeine?
Caffeine is a naturally occurring substance found in nuts, seeds, and leaves of a number of different plants including kola nut, cacao bean, yerba mate, and guarana berries. It is odorless and has an extremely bitter taste. Caffeine is a stimulant that speeds up messages traveling between the brain and the body1.
How does it affect the body?
As a stimulant, caffeine works to keep you alert. Once ingested, caffeine enters the bloodstream within 15 minute2. Caffeine crosses the blood-brain barrier where it binds to the adenosine receptors. Adenosine promotes and suppressed arousal, however caffeine blocks these actions, speeding up cells and boosting feelings of alertness. This happens about an hour after consumption. However, caffeine has a half-life of about 3-5 hours which means 3-5 hours after ingestion, half the caffeine consumed is still in your system3. As caffeine is metabolised and the levels drop, adenosine will again be able to do its sleep-inducing role.
Sources of caffeine
Caffeine is naturally found in more than 60 plants including coffee beans, cocoa beans, tea leaves and kola nuts, and is also added to foods such as energy drinks, cola soft drinks, lollies and sports supplements. The table below shows the caffeine content of common foods and beverages4.
|Food or beverage||Caffeine content|
|Espresso||145mg per 50ml cup of coffee|
|Energy drink||80mg per 250ml can|
|Instant coffee||80mg per 250ml cup (1 teaspoon instant coffee)|
|Black tea||50mg per 220ml cup|
|Cola drinks||36mg per 375ml can|
|Milk chocolate||10mg per 50g bar|
How much caffeine is ok each day?
A recommended daily intake of caffeine does not exist. Both the US Department of Agriculture (USDA) and European Food Safety Authority (EFSA) consider a daily intake of 400mg of caffeine (equivalent to 2-4 cups of coffee) to be safe5. However, it is recommended to limit the amount of caffeine you consume at any one time to 200mg, as fatal overdoses have been reported with single doses of 500mg of caffeine6. Pregnant women should limit their daily caffeine intake to no more than 200mg7.
For children, there is currently no safe level of caffeine consumption in Australia. Food Standards Australia New Zealand (FSANZ) reports that a dose of 95mg of caffeine in children aged 5-12 results in disrupted sleep8. At doses of 100-400mg, they experience increased nervousness and jitteriness. Therefore, it’s best to avoid caffeine-containing beverages until high school and even then adolescents should keep their intake to a minimum, as caffeine can affect how the body absorbs calcium, reducing the amount available for growing bones9.
Health benefits of caffeine
In the right amount, caffeine can have both mental and physical benefits. Caffeine can increase attention, alertness and memory, while physically it can help us train for harder and longer because it alters how hard we think the exercise is10. Research shows caffeine may also reduce the risk of Alzheimer’s disease and dementia11, while those who consume more caffeine have been found to have a lower risk of kidney stones12.
Health risks of caffeine
Too much caffeine can increase anxiety, make you restless, give your headaches and impair your sleep13. As a stimulant, caffeine makes the heart beat a little faster and increases blood pressure. For most of us, this increase heart rate isn’t a problem, however, if you have too much caffeine or are oversensitive your heart rate may rise too high and stay elevated for too long or even give you heart palpitations (a weird rhythm). In addition, caffeine can easily cross the placenta, increasing the risk of miscarriage and low birth weight which is why lower recommended intakes exist for pregnant women14. Caffeine can also negatively interact with some medications, so make sure you check with your doctor or health care professional.
- Australian’s attitude towards coffee. Available at URL https://mccrindle.com.au/insights/blogarchive/australian-attitudes-towards-coffee/ Accessed February 2021.
- Heckman M, Well J and Gonzalez De Mejia E. Caffeine (1, 3, 7-trimethylxanthine) in foods: a comprehensive review on consumption, functionality, safety and regulatory matters. Journal of Food Science 2010;75(3):R77-R87.
- Fredholm B. Adenosine, adenosine receptors and actions of caffeine. Pharmacol Tocicol 1995;76:93-101.
- Food Standards New Zealand Australia. Caffeine. Available at URL https://www.foodstandards.gov.au/consumer/generalissues/Pages/Caffeine.aspx Accessed February 2021.
- Scientific Report of the 2015 Dietary Guidelines Advisory Committee. Available at URL https://health.gov/sites/default/files/2019-09/Scientific-Report-of-the-2015-Dietary-Guidelines-Advisory-Committee.pdf Accessed February 2021.
- Holmgren P, Norden-Pettersson L & Ahlner J. Caffeine fatalities – four case reports. Forensic Sci Int 2004 Jan 6;139(1):71-73.
- ACOG Committee Opinion No 462: Moderate caffeine consumption during pregnancy. Obstet Gynecol 2010 Aug;116(2 Pt 1):467-468.
- American Bone Health. Available from URL Kids and Caffeine. https://americanbonehealth.org/young-athletes/kids-and-caffeine/ Accessed February 2021.
- Caffeine. Available at URL https://www.foodstandards.gov.au/consumer/generalissues/Pages/Caffeine.aspx Accessed February 2021.
- Scientific opinion on the safety of caffeine. EFSA Journal 2015;13(5):4102. Available at URL https://efsa.onlinelibrary.wiley.com/doi/epdf/10.2903/j.efsa.2015.4102 Accessed February 2021
- Eskelinen M & Kivipelto M. Caffeine as a protective factor in dementia and Alzheimer’s disease. J Alzheimers Dis 2010;20 Suppl 1:S167-174.
- Ferraro P, Taylor E, Gambaro G & Curhan G. Caffeine intake and the risk of kidney stones. Am J Clin Nutr 2014 Dec;100(6):1596-1603.
- Reissig C, Strain E & Griffiths. Caffeinated energy drinks – a growing problem. Drug Alcohol Depend 2009 Jan 1; 99(1-3):1-10.
- Chen L, Neelakantan N et al. Maternal caffeine intake during pregnancy is associated with risk of low birth weight: a systematic review and dose-response meta-analysis. BMC Medicine 2014;12:174