Caffeine is found in the leaves, seeds, and fruits of over 60 plants worldwide. Caffeine naturally occurs in tea, coffee, and chocolate. It is added to ‘cola’ type soft drinks and energy drinks.
Caffeine has a stimulant effect on your central nervous system. This can help the brain to produce faster and clearer thoughts, take away feelings of tiredness and improve exercise performance.
Too much caffeine can cause irritability, anxiety, an increase in heart rate, and insomnia. It all depends on the rate that your body metabolises caffeine and how much caffeine you usually have (as our bodies can acquire a tolerance to the effects of caffeine). Quick metabolisers process caffeine fast, while slow metabolisers eliminate the caffeine more slowly and can feel the effects many hours afterwards.
Often you may hear that caffeine has a diuretic effect (increases the rate of urination): this is true, but in a cup of tea and coffee there is plenty of fluid to offset these losses.
There are no firm recommendations on caffeine consumption- how much caffeine you can have will depend on your individual response to it. For the general population, 400mg or 3 cups of coffee each day has been determined to be safe, however, you should have less if you are more sensitive to caffeine (e.g. you get anxious or jittery) (EFSA, 2015; FSANZ, 2021).
Source: Ministry of Health, 2020 (Figure 4)
*Note these are rough estimates, the caffeine in food and drink can change with different brands, cafés and brewing times.
Caffeine has a long half-life, which means it lingers in your bloodstream for a long time. Even if you fall asleep fine, caffeine still in your system past bedtime can disrupt the quality of your sleep. For this reason, it is recommended that you avoid consuming caffeine past the late afternoon (e.g. past 2-4 pm) (Sleep Foundation, 2022).
For more information about caffeine, click to read the attached article from Professor Elaine Rush
Last reviewed 01/06/2022
Last modified: July 1, 2022