CYP1A2
Cytochrome P450 1A2
What it does
CYP1A2 produces a liver enzyme responsible for breaking down the majority of the caffeine you consume. How active your version of this enzyme is determines how long caffeine stays active in your body.
The variants that matter
A common variant separates fast metabolisers, who clear caffeine quickly, from slow metabolisers, in whom caffeine can remain active for up to ten hours instead of around four. Roughly half of adults fall on the slow side.
If you carry the notable variant
If you are a slow metaboliser, an afternoon coffee can still be in your system at bedtime, disrupting sleep, and some research links slow metabolism plus heavy intake to other effects. Fast metabolisers clear it before it troubles their sleep.
Why it matters in India
Caffeine metabolism varies widely across Indian populations, and with chai and coffee both deeply embedded in daily life, knowing whether you clear caffeine slowly is one of the simplest useful things to learn about your body.
The honest caveat. This gene affects clearance speed, not sensitivity. A separate gene, ADORA2A, governs how strongly you feel caffeine, so a fast metaboliser can still be jittery and a slow one relatively unbothered while awake.