CYP1A2 – Breaking down caffeine and more


Liver DetoxGenesThis is part of an ongoing series on the genes involved in detoxification.

The CYP1A2 enzyme is involved in the metabolism of xenobiotics (caffeine, aflatoxin B1, and acetaminophen) and is induced by the polycyclic aromatic hydrocarbons (PAH’s) that are found in cigarette smoke.  It metabolizes some PAH’s into carcinogenic intermediates.

CYP1A2 is also induced (activated) by cruciferous veggies such as cabbage, cauliflower, and broccoli.  It is inhibited by cumin, turmeric, peppermint, chamomile, dandelion, and St. John’s wort.  There is a list of drugs, inducers, and inhibitors of CYP1A2 on Wikipedia.  Popular drugs that are metabolized, at least partially,  by CYP1A2 include Wellbutrin, Zyprexa, and Cymbalta — as well as caffeine.

In looking at CYP1A2, some polymorphisms increase activity and some inhibit activity.  So what are the consequences of inhibition or increased activity?  Well, it depends…   CYP1A2 metabolizes some pro-carcinogens from tobacco smoke into carcinogens.  It also is involved in turning aflatoxins (mold found on grain) into active compounds involved in liver cancer.  So the rate at which the toxins are metabolized, in conjunction with how well Phase II detoxification is doing at moving out the metabolites, all affect the risk of certain cancers.  For example, slow or inactive CYP1A2 is thought to decrease the risk of liver toxicity from aflatoxin B.

One of the fun things to find out from your CYP1A2 genes is whether you are a fast or slow metabolizer of caffeine.  (Of course, you probably already know how you react to caffeine, but it is nice to see the science behind it :-)

Check your 23andMe results for rs762551 – CYP1A2 gene:

  • AA: Fast metabolizer of caffeine – increased enzyme activity
  • AC:  medium caffeine metabolizer [study]
  • CC: slower caffeine metabolizer (CYP1A2*1F)


Other polymorphisms have also been shown to decrease the activity of this gene as well:

Check your 23andMe results for rs12720461:

  • CC: normal
  • CT:  decreased activity (carrier of one CYP1A2*1K allele)
  • TT: decreased activity (CYP1A2*1K )


Check your 23andMe results for rs56276455:

  • AA: decreased activity (CYP1A2*3)
  • AG:  decreased activity (carrier of one CYP1A2*3 allele)
  • GG: normal


Check your 23andMe results for rs28399424:

  • TT: decreased activity or inactive (CYP1A2*6)
  • CT:  decreased activity (carrier of one CYP1A2*6 allele)
  • CC: normal


Check your 23andMe results for rs72547517:

  • AA: decreased activity or inactive (CYP1A2*8)
  • AG:  decreased activity (carrier of one CYP1A2*8 allele)
  • GG: normal


Check your 23andMe results for rs72547515:

  • AA: decreased activity or inactive (CYP1A2*16)
  • AG:  decreased activity (carrier of one CYP1A2*16 allele)
  • GG: normal


Diet and Supplements:

Though polymorphisms do play a role in CYP1A2 enzyme activity, interactions with environment and foods that you eat are also very important here.  If you are taking a drug that is metabolized by CYP1A2, you should look at both your genetics and at what you are eating and/or smoking.

Curcumin is an inhibitor of CYP1A2 in humans and in animals.  A recent animal study found that curcumin prevented liver damage from aflatoxin B exposure.  A potent carcinogen, aflatoxin B is a toxin produced by mold (Aspergillus) and sometimes found in peanuts, corn, and other grains.  Curcumin can be found in supplements and in the spice, turmeric.

More to Read:


Updated 5/2017

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