There are 2 variants (called allele) of this gene which means that a small section of the CYP1A2 gene has a different nucleotide (building block of nucleic acid) and is marked by A->C substitution at position 734. (1, 2)
Each of us has two copies of the CYP1A2 gene, one inherited from each parent. These different variants are:
- Gene CYP1A2*1A (high activity),
- Gene CYP1A2*1F (low activity)
The resulting combination of these gene variants determines if you are a slow or a fast caffeine metabolizer.
Fast caffeine metabolizers have both fast variants – CYP1A2*1A.
In other words, they are homozygous CYP1A2*1A + CYP1A2*1A (fast variant + fast variant).
Slow caffeine metabolizers have at least one slow variant – CYP1A2*1F.
Please click here to read more on the topic of the impact of genes on caffeine intake.