CYP1A2Is there a caffeine gene? What CYP1A2 really says about your coffee
Two friends share a coffee at 3 p.m. One sleeps like a baby. The other is still awake at midnight.
Is it genetic? Partly. There is a "caffeine gene", and it is called CYP1A2. But it doesn't work quite the way most websites say.
What does CYP1A2 do?
When you drink coffee, your liver starts clearing the caffeine right away. CYP1A2 is the gene for the enzyme that does almost all of that work. The faster it works, the sooner your coffee wears off.
For most people, half the caffeine from a cup is gone in about five hours. Some people clear it much faster, some much slower. Your genes are one reason. Smoking, pregnancy, age and some medicines, including the pill, change the speed too.
Fast or slow: what does your result mean?
Your DNA file shows CYP1A2 as two letters at a spot called rs762551.
| Your file shows | What it means | In your Helisoma report |
|---|---|---|
| AA | Fast version, twice | Clears caffeine fast |
| AC | One fast, one slower | Average caffeine clearance |
| CC | Slower version, twice | Slow to clear caffeine |
AA is the most common result. In the study that found this gene, about half the people were AA and only 1 in 10 was CC.
The catch: it matters most if you smoke
Smoking speeds up the caffeine enzyme. The fast version speeds up even more. So in smokers, AA people clear coffee much faster than everyone else. In non-smokers, researchers found almost no difference.
That explains a common surprise: when people quit smoking, their usual coffee suddenly feels much stronger. The enzyme slows down, so the caffeine stays longer.
Why does coffee make some people jittery?
That is a different gene: ADORA2A. Caffeine wakes you up by blocking a "time to rest" signal in your brain, and ADORA2A builds the place where that signal lands. In one study, people with a certain version felt clearly more anxious after one or two cups' worth of caffeine. At a big dose, most people felt anxious, whatever their genes.
So there are two separate things: how fast you clear caffeine, and how strongly you feel it.
Does CYP1A2 decide how coffee affects my sleep?
So far, no study has shown that. A study of more than 6,000 children who drank caffeine found that the more caffeine they had, the less they slept. Their CYP1A2 and ADORA2A versions made no difference. The amount of caffeine did.
How do I find my result?
Open your raw DNA file in any text editor and search for rs762551. The two letters at the end of the line are your answer, for example rs762551 15 75041917 AC. AncestryDNA shows the letters in two columns (A C). Not sure how to get the file? Here is how.
Or just drop the file into our free analysis. Your browser reads it in about a minute, the file never leaves your device, and your full report shows your caffeine results with the study behind each one.
So when should I have my last coffee?
Try it on yourself:
- For two weeks, have your last coffee before noon. Note how you sleep.
- For the next two weeks, have one at 3 p.m. Compare.
- If one strong cup makes you shaky, try half a cup before you give up coffee.
Your own nights will tell you more than any gene.
Sources
- Sachse C, Brockmöller J, Bauer S, Roots I. Functional significance of a C-to-A polymorphism in intron 1 of the cytochrome P450 CYP1A2 gene tested with caffeine. British Journal of Clinical Pharmacology, 1999. PubMed 10233211
- Nehlig A. Interindividual differences in caffeine metabolism and factors driving caffeine consumption. Pharmacological Reviews, 2018. PubMed 29514871
- Childs E, Hohoff C, Deckert J, et al. Association between ADORA2A and DRD2 polymorphisms and caffeine-induced anxiety. Neuropsychopharmacology, 2008. PubMed 18305461
- Jessel CD, Narang A, Zuberi R, Bousman CA. Sleep quality and duration in children that consume caffeine: impact of dose and genetic variation in ADORA2A and CYP1A. Genes, 2023. PubMed 36833216
