Have you ever wondered why one person can guzzle strong coffee all day long without feeling a thing, while another feels anxious and jittery after a single cup of cappuccino at breakfast?
Such a diverse response can be attributed to individual differences in metabolism of caffeine. Caffeine is metabolized (i.e. processed) in the liver by an enzyme called CYP1A2. This enzyme is made in accordance with “instructions” received from the CYP1A2 gene. Inborn variations in this gene determine how active resultant CYP1A2 enzyme is. Individuals with an active CYP1A2*1A variation are the so-called “fast” caffeine metabolizers, whereas carriers of the less active CYP1A2*1F variation are known as “slow” caffeine metabolizers.
Slow metabolizers have trouble breaking down and eliminating caffeine, therefore, it stays in the system for longer and has a more stimulating effect. Fast metabolizers can process and eliminate caffeine very efficiently.
If coffee causes you unpleasant symptoms, you might be one of those “slow” caffeine metabolizers. Anxiety, inability to concentrate, heart palpitations and insomnia after relatively small amounts of coffee may suggest that your body is struggling with breaking caffeine down and getting rid of its metabolites. You might want to consider switching to beverages which contain less or no caffeine.
Herbal teas (e.g. mint, hibiscus and rooibos ) are caffeine-free. Black and green tea contain some caffeine, ranging between 20 -75mg and 30 – 50mg per 250ml cup respectively.
Theoretically, a standard 235ml cup of coffee contains about 100mg of caffeine. However, the exact amount of caffeine in coffee strongly depends on the type of bean used and the duration of brewing. Robusto beans contain twice as much caffeine as their arabica counterparts.
Longer brewing time increases caffeine content. Drip brewed coffee, with a brewing time of around 5 minutes, contains most caffeine (roughly 150 – 175mg per standard cup). A French press brews for 2-3 minutes, resulting in slightly less caffeine (110-135mg). A shot of espresso has even less caffeine (80mg per shot) because the coffee is in water for just 20-30 seconds. This might sound low, but a single shot is typically 50-60 ml, so if you take multiple cups through the day your caffeine exposure will increase quickly.
