# CYP1A2 — Cytochrome P450 1A2
URL: https://genohealth.app/genes/cyp1a2
Category: Detoxification
Chromosome: 15q24.1
Key variants: rs762551
Last reviewed: 2026-04-25

## Summary
CYP1A2 metabolizes ~95% of the caffeine you consume. The rs762551 variant defines fast vs slow metabolizers. Slow metabolizers who drink 2+ cups of coffee/day face elevated cardiovascular risk; fast metabolizers may actually benefit from moderate intake.

## What it does
CYP1A2 is the liver enzyme that breaks down caffeine, melatonin, several antipsychotics and antidepressants, and aromatic amines from char-grilled meat. Activity varies up to 40-fold between people based on genetics (rs762551) and induction by smoking, cruciferous vegetables and certain medications.

## Why it matters
Slow metabolizers (AC or CC at rs762551) who drink 2+ cups of coffee per day have elevated risk of hypertension, non-fatal myocardial infarction, and impaired glucose tolerance. Fast metabolizers (AA) may benefit from moderate coffee for cardiovascular and metabolic health. Caffeine sensitivity, sleep disruption and afternoon-crash patterns are practical signals.

## Variants
- rs762551 (CYP1A2*1F (A→C)) — risk allele C; C allele reduces enzyme inducibility; slower caffeine clearance. (frequency: C allele ≈30-40%)

## Genotypes
- **AA (fast metabolizer)** (~40%): Caffeine cleared rapidly (half-life ~3-4h). → Moderate coffee (2-4 cups/day) often cardioprotective and metabolically neutral. Stop caffeine ~6h before sleep.
- **AC or CC (slow metabolizer)** (~60%): Caffeine lingers (half-life ~6-10h). → Cap caffeine at 200 mg/day (~1 cup of coffee). No caffeine after noon. Track resting BP if you drink daily.

## Conditions
- **Hypertension** — Increased risk in slow metabolizers with high intake: Slow metabolizers drinking 2+ cups/day have ~50% higher hypertension risk.
- **Non-fatal myocardial infarction** — Increased risk in slow metabolizers: Cornelis 2006 JAMA: slow metabolizers showed dose-dependent MI risk; fast metabolizers showed protection.
- **Impaired glucose tolerance** — Increased in slow metabolizers: High-dose caffeine impairs insulin sensitivity acutely; effect more pronounced in slow metabolizers.
- **Drug metabolism** — Affects clozapine, olanzapine, theophylline, melatonin clearance: Relevant for psychiatry and pulmonology dosing.

## Diet
Rationale: Diet can modestly tune CYP1A2 activity, but the main lever is caffeine dose itself, matched to genotype.
Prioritize: Cruciferous vegetables (broccoli, brussels sprouts, cabbage) — induce CYP1A2 modestly; Adequate protein (supports phase-I detox); Water and electrolytes (mitigate caffeine diuresis)
Limit: Char-grilled and blackened meat (CYP1A2 substrates → carcinogenic intermediates); Excessive caffeine (especially if slow metabolizer); Energy drinks (combination of caffeine + other CYP1A2 substrates)

## Lifestyle
- Track resting blood pressure if you drink coffee daily (>1 cup).
- Set a caffeine cutoff: noon for slow metabolizers, 2 PM for fast.
- Smoking strongly induces CYP1A2 — quitting can transiently raise caffeine and clozapine levels (medical relevance).
- If you take psychiatric medications metabolized by CYP1A2, discuss caffeine timing with your prescriber.

## Supplements
- **L-theanine** — 100-200 mg with each caffeinated drink, form: Suntheanine. Smooths caffeine response; reduces jitter without blunting alertness.
- **Magnesium glycinate** — 200-400 mg/day, ideally evening, form: Glycinate. Counteracts caffeine-induced magnesium loss; supports sleep.
- **Sulforaphane (broccoli sprout extract)** — 10-30 mg/day, form: Standardized extract. Induces phase-II detox enzymes downstream of CYP1A2.

## Contraindications
- Slow metabolizers on hormonal contraceptives — estrogen further inhibits CYP1A2; caffeine effects amplified.
- Pregnancy — CYP1A2 activity drops, caffeine half-life can triple; limit to <200 mg/day regardless of genotype.

## FAQ
**Q: How do I know if I am a slow caffeine metabolizer?**
A: Beyond a DNA test, signs include feeling jittery for many hours after one coffee, disrupted sleep from afternoon caffeine, racing heart from a single espresso, or persistent afternoon energy from morning coffee.

**Q: Is coffee bad for slow CYP1A2 metabolizers?**
A: 1 cup/day or less is generally fine for most slow metabolizers. The risk signal appears at 2-4+ cups/day, especially with hypertension or family history of cardiovascular disease.

**Q: Does CYP1A2 affect tea the same as coffee?**
A: Tea contains less caffeine and adds L-theanine, which buffers the response. Slow metabolizers often tolerate moderate tea (2-3 cups) better than equivalent coffee.

**Q: Should slow metabolizers drink decaf?**
A: Decaf is a reasonable swap if you enjoy the ritual. Note that decaf still contains 5-15 mg caffeine per cup — meaningful if you drink several.

**Q: Why does my partner handle coffee fine but I don't?**
A: Likely a CYP1A2 genotype mismatch. AA fast metabolizers clear caffeine 2-3x faster than CC slow metabolizers. Genetic testing makes the difference visible.

## Citations
- Cornelis et al., JAMA 2006 (PMID 16522833): Slow CYP1A2 metabolizers had dose-dependent MI risk with coffee; fast metabolizers showed inverse association.
- Palatini et al., J Hypertens 2009 (PMID 19451835): Slow metabolizers had increased hypertension risk; fast metabolizers did not.
- Guessous et al., Mol Nutr Food Res 2012 (PMID 22504888): Review of CYP1A2 polymorphisms and coffee-disease associations.

Disclaimer: Informational only — not medical advice.