Caffeine is one of the most widely consumed stimulants in the world. It is found naturally in the leaves and seeds of many plants such as tea, coffee and cocoa, and artificially in some soft drinks, energy drinks and some painkilling drugs. Caffeine is metabolised in the liver by the enzyme cytochrome P450 1A2. The CYP1A2 gene encodes the enzyme responsible for caffeine metabolism. Different allelic variants for the SNP rs760551 of this gene result in different levels of enzyme activity and thus different rates of caffeine metabolisation. The possible phenotypes for the marker are fast metaboliser or slow metaboliser, and therefore the stimulant effects of caffeine will depend on this rate of metabolisation. If you carry a C allele, i.e. if your genotype is CC or AC, then you are a slow metaboliser of caffeine and therefore have an increased risk of hypertension and myocardial infarction associated with caffeine consumption. Conversely, if your genotype is AA, you are a fast metaboliser of caffeine and have a lower vascular risk associated with caffeine consumption.