How sensitive are you to Caffeine?

If you are anything like me, I love caffeine. I love the taste of a good coffee, but I also love caffeine in other forms such as pills (e.g. NoDoz, Vivarin) and especially chocolate.  I love how it makes me feel.  The highs, the positive change in mood, and the attitude that I can take on the world! 

Unfortunately, not everyone feels...or in this case reacts the same way that I do when I consume caffeine.    

So why the difference? Just plain old genetics. Yes, your genetics determines how sensitive your body is to caffeine.  Remember the person you talked to last week and she said caffeine does nothing for her?  And then you look at her like she has three heads?  Well, maybe that is not your experience but it has certaily been mine on a number of occasions.  I've come across a number of people who have stated that caffeine has little to no effect on them. 

So what is happening here?  Just like many things that we consume, caffeine is metabolized in the liver and is broken down by an enzyme CYP1A2.  But not all people can produce the same amount of this enzyme because production of this enzyme is regulated by the CYP1A2 gene.  Yes, there is a gene for that. 

But not so fast.  Another gene, the AHR gene also plays a role in caffeine sensitivity.  This gene regulates the turning on and off of the CYP1A2 gene.  

And taking up the rear are the adenosine receptors in the brain which also play a role in caffeine sensitivity.

Caffeine has an average life span of approximately 4 hours.  Depending on how a person's body metabolizes the caffeine determines the effect that the caffeine may have.  

Have you ever seen a person drink a cup of coffee within a few hours of going to bed and this person still gets a full night's sleep?  This person would be considered hyposensitive to caffeine or fast metabolizers.  People who fall into this category can consume two to three times the amount of caffeine the average person consumes with minimal effect.  

In the report published by Coffee and Health, Genetics, metabolism and individual responses to caffeine, sensitivity to caffeine is broken down into three groups:

High Sensitivity 

Slow-metabolism in the liver and high binding in the central nervous system. Even small amounts of caffeine will cause a stimulating effect and higher doses may cause sleep problems, as seen in a minority of people.

Regular sensitivity

The balance between caffeine inactivation in the liver and binding in the central nervous system means that the individual can typically drink 2–5 cups of coffee during the day but without adverse reactions or sleep disturbances. Caffeine is normally not recommended in the evening, but individual differences prevail, as seen in most people.

Low sensitivity 

Fast-metabolisers of caffeine. Higher intakes can be consumed, (although healthcare professionals should advise that they still stay within the EFSA guidelines of no more than 5 cups of coffee per day13). Coffee drinking before bedtime does not typically disturb sleep.

So what category are you?

There are a number of tests that a person can take including in-home caffeine tolerance tests, which can help you to determine your caffeine sensitivity level. The price range for these tests range from $25 to $160 (or you can get one on eBay for $10).  The higher priced tests usually test for other food and non-food sensitivity items. 

Test yourself.  We'd love to know what you find out.  Add comments below. 

Kallmyer, T. (2018, July 2). Caffeine Sensitivity. Retrieved November 12, 2019, from https://www.caffeineinformer.com/caffeine-sensitivity.