Find out how Coffee affects you: The CYP1A2 Gene

Disclaimer: This is an educational and informative post, nothing in it is meant to take the place of medical treatment, neither does it claim to treat, cure or diagnose any condition.


Ever wondered why some people can drink coffee right before bed and sleep like a brick, while others are bouncing off the walls all night?

This has to do with either being a Fast metaboliser or a slow metaboliser of caffeine.


The CYP1A2

Caffeine is mainly metabolized by the CYP1A2 enzyme in the liver.The status of your CYP1A2 determines how fast your body clears the caffeine you drink from your system.

It takes about 5 hours to lower caffeine levels by half, the half-life of caffeine. In other words, if you drink 4 cups of coffee (160g of caffeine) Half of that(80g) will still be in your system 5 hours later.

You may begin experiencing the effects of caffeine right after consuming it, and the effects will continue to last for as long as the caffeine remains in your body.


A fast Metaboliser

A fast metaboliser is someone who carries the AA allele. They have the ability to metabolize caffeine at a much faster rate and thus clear caffeine from their systems. In these people coffee is unlikely to cause high blood pressure and raise cortisol levels. Drinking coffee first thing in the morning is likely to make you feel more alert but without the jitters and spike in blood pressure.

A Slow Metaboliser

However, a slow metaboliser, (one who carries the C allele) has a much slower enzymatic activity and takes longer to metabolize caffeine. The result is that caffeine metabolisers take between 8-10 hours to drop caffeine levels by half.

Slow metabolisers have an increased risk of impaired fasting glucose, hypertension and disrupted sleep.


What is a moderate and safe amount of caffeine per day?

This is determined by your genotype. For AA alleles 5 cups a day (200mg) would be moderate but for a C allele this would be 2 cups (80mg).


Benefits of Caffeine in moderation:

  • Rich in Polyphenols, antioxidants found in plants (cancer protecting)
  • Studies show caffeine can protect against Parkinson’s Disease.
  • Can improve alertness,memory and overall mood.
  • Can increase sports performance and endurance.

Risks of Caffeine :

  • can spike blood pressure
  • can impair fasting glucose
  • can raise cortisol levels
  • can disrupt sleep and cause insomnia
  • can contribute to anxiety
  • can mess with your endocrine system (hormones)


  1. Postprandial glycaemic and lipaemic responses to chronic coffee consumption
    may be modulated by CYP1A2 polymorphisms, British Journal of Nutrition (2018)doi:10.1017/S0007114518000260
  2. How to Tell if You Are a Fast or Slow Caffeine Metabolizer by Dr. Aaron Gardner, BSc, MRes, PhD,March 1, 2023

  3. My own training as a genetic practitioner.

Interested in finding out what allele of this gene you carry? Contact me

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