Caffeine Sensitivity

genes and caffeine sensitivity

Caffeine sensitivity is determined by the efficiency of the human body to process and metabolize caffeine.

This shouldn’t be confused with caffeine tolerance, which describes how the body responds to caffeine over time.

Sensitivity has more to do with a person’s unique genetic makeup as this determines to what degree a given amount of caffeine will affect a person.

Genetic Link to Caffeine Sensitivity

Caffeine is metabolized by the liver using the enzyme CYP1A2. The ability to produce this enzyme is regulated by the CYP1A2 gene. Slight changes in the DNA sequence of this gene determine how efficiently a person can metabolize caffeine and thus eliminate it from the body.¹

Some people genetically produce very little of this enzyme while others produce a large amount. The majority of humans are somewhere in the middle.

The AHR gene also plays a role in caffeine sensitivity in that it regulates the turning on and off of the CYP1A2 gene. 10% of the population are rapid caffeine metabolizers and thus not very caffeine sensitive. ²

The third genetic link to caffeine sensitivity involves the type of adenosine receptors a person has in his/her brain. Those lacking the correct adenosine receptors in their brain are unresponsive to the awakening effects of caffeine because the caffeine molecule cannot properly bind to the receptors. ³

6 More Genetic Links

The most recent research from The Harvard School of Public Health found 6 new genetic variants associated with the way people metabolize and form addiction to caffeine.4

The 120,000 person study revealed:

  • 2 genes related to how caffeine is metabolized.
  • 2 genes associated with how we feel rewarded from caffeine.
  • 2 genes that regulate fat and sugar in the bloodstream as a response to caffeine.

More research in Italy and the Netherlands has shown the gene PDSS2 may also be responsible for speed of metabolism. People with a specific variation drink less coffee than others. It is thought that the PDSS2 dictates sensitivity at lower levels of consumption, while CYP1A2 determines consumption at higher caffeine levels.

Three Levels of Caffeine Sensitivity

Based on the genetic data we have to date, we can identify people with 3 distinct levels of caffeine sensitivity, which in turn determines to what degree the effects of caffeine will be realized.

1. Hypersensitive to Caffeine

These people react to very small amounts of caffeine. Even at amounts less than 100 mg, people who are hypersensitive to caffeine can experience overdose symptoms such as insomnia, jitters, and an increased heartbeat.

For these people, it can take as much as twice as long for caffeine to metabolized. 

2. Normal Sensitivity to Caffeine

People who show normal sensitivity to caffeine can usually have 200-400 mg of caffeine daily without any adverse reactions. These people have no trouble sleeping as long as the caffeine is consumed early enough in the day.

The majority of humans fall under this category and this group is what the recommended daily safe dose of caffeine has been established for. 

3. Hyposensitive to Caffeine

About 10% of the human population are hyposensitive to caffeine. They process caffeine so efficiently that these people report taking large doses ( >500 mg) without much effect at all. Those hyposensitive can also consume caffeine shortly before bedtime and still get a good night’s sleep.

These people are more prone to consuming large doses of caffeine in order to get the desired effects. 

Determining Your Level

3 levels of sensitivity
In order to safely use caffeine, it’s important to understand your level of caffeine sensitivity.

Based on the three descriptions above, you should be able to identify your level of caffeine sensitivity and then follow our recommendations below.

  1. For those hypersensitive to caffeine, we recommend that they cautiously consume caffeine and avoid highly caffeinated beverages like coffee and energy drinks. Black tea or green tea is probably a wise choice for this group.  Quitting caffeine altogether may be an even better option.
  2. Those with normal sensitivity should be aware of how much caffeine they are consuming and keep this within the daily safe dose guidelines of between 300-400 mg. This equates to 2-3 cups of brewed coffee (not Starbucks), two 16 fl.oz. energy drinks, 7-8 cups of black tea.
  3. Hyposensitive people should evaluate the necessity of caffeine. If large amounts of caffeine do not create the desired effects such as wakefulness, alertness, and productivity, then we would question the benefits of consuming it. Since caffeine is toxic, large doses daily could be doing damage over time, which isn’t yet fully understood.

Caffeine Sensitivity Isn’t Exactly Black and White

While the above guidelines and caffeine sensitivity levels may apply to many, there are some that could fall somewhere in the middle.

Some people could be normal but lean toward the hypersensitive category or learn toward the hyposensitive category. Human genetics are complex and people are unique with many subtle genetic variations.

Also, some people can develop caffeine hypersensitivity over time instead of from having it from birth.

If you don’t align perfectly in one of the sensitivity categories above, it’s okay!

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  • boo

    done jdghasdh baannnanasss

  • Beatrue

    What an amazingly informative site. Thank you for putting this together.

    I think I’ve developed hypersensitivity as my body feels shagged after just a mouthful of dregs! My poor body has grown hypersensitivite, probably extra care is needed – I had thyroid cancer 3 years ago and I no longer have a thyroid, so my adrenals are likely to be overworking.

    Good to listen to our bodies. We’re all different and we change over time. What was once good is now unbearable for me.

  • Linn

    I first starting drinking Diet Coke in college 25 years ago and one can would give me the jitters. I gradually added coffee and have become a 1-2 cup every morning person with an occasional afternoon DC. With the relatively small amount I drink I figured it couldn’t be that much of a problem, but now I think I am on the hypersensitive side. I switched to one cup of half-caff almost a week ago and I already feel more peaceful and less anxious and more steadily awake all day rather than awake in the morning and crashing in the afternoon. I’m also less hungry and feel that my blood sugar is steadier. I do have fatigue at night but I think this is withdrawal. So I think it is true that everyone’s tolerance is different. I’m going to keep stepping down, in a couple of weeks I’m going to switch to black tea and I may try stopping it altogether in the new year.

  • David Hughes

    I only started drinking coffee about ten years ago but like it although unknowingly it was the root cause of my GERD and possibly liver problems. Stopping all caffeine; coffee, tea and energy drinks cured my GERD no more nuclear powered heartburn. I guess I’m in the hypersensitive category.

  • Josh Speer

    I can drink 2 monsters before bed and have no ill effects….coffee at night is a norm…runs in my family. Now…I will get a headache if I am consuming 300mg of caffeine a day and then go cold turkey.

  • Guest

    Thats what i did from age 17-24 until i got a heart attack at age 24, now i just barely drink cup of coffee a day.. Good Luck !!

  • poo poo pee pee

    haha I find that hard to believe

  • Josh Speer

    Blame your caffeine for the bad diet…that’s fine. I don’t agree with you. Caffiene is consumed by millions of consumer and they never give medical consideration in the area of “heart attacks”…headaches in withdrawal symptoms “yes”. I would argue that this could actually help prevent heart attacks by stimulating the heart muscle. I have grandfather that has had a triple bypass and several heart attacks and he drinks coffee…it is actually healthy for him.

  • Glenn

    Is it normal to have rapid heartbeats at the beginning of the withdrawal process? I have hypocalcemia, because I used to drink coffee and now I can no longer tolerate it. Even a small cup of coffee makes my heart go crazy. I’m quitting but I still have those uncomfortable palpitations and I wonder if it’s related to the detox.

  • Ted

    It could be, if it doesn’t clear up in a day or two you really should see your doctor.

  • Aidan MacLeod

    I started drinking coffee in highschool, and have been drinking tea at night since I was quite young. I never had any adverse effects until my senior year of high school, when I got a concussion. Afterwards, and still to this day, I am unable to drink caffeine without it affecting me for hours afterwards. Even 12 hours later, a cup of coffee will prevent me from sleeping, and I often get jittery, which never happened before. Is this a common side effect of concussions?

  • Ted

    Probably not related to your concussion but your age. As we age certain genes can turn on or off, some of which influence the way we metabolize caffeine.

  • Alliya

    I have always been super hypersensitive to caffeine. The minutest amount of caffeine affects me negatively. I cannot even have Jasmine tea! This is so annoying, I lose out on the benefits of amazing teas. Both my parents were coffee drinkers without any ill effects. Anything I could do to change this?

  • Ted

    Unless you can change your DNA, I’m afraid not.

  • Max

    I’m sensitive too! It’s quite easy change this! Just drink your favorite caffeine beverage every day. If you drink caffeine one day and one not, you risk to become more sensitive. I’ve tried this and it works! have fun with caffeine! 😉

  • Ted

    I’m not sure that’s great advice, some people really can’t process caffeine because of their genetics and will not build up a tolerance to it as you did.

  • su

    Hi. Perhaps in your withdrawl process your sensitivity to caffeine is altered. However, if you regularly take caffeine with milk this may contribute to hypocalcemia. Try eating a banana as well. Perhaps you have a caffeine allergy? Check a doctor!

  • Kacey

    Redbush tea is naturally caffeine free, as is green tea. Green tea can now come in a range of flavours such as gingerbread, caramelised apple and mango and strawberry. Redbush tea is a really lovely one that you can drink with milk for a very standard cuppa, just with a nice earthy taste. You can also buy flavoured redbush, such as vanilla, which is nice. 🙂

  • Rich

    I don’t think it’s accurate to say that tea-sourced caffeine would be more beneficial than coffee sourced caffeine. Although tea is typically made weaker than coffee and therefore has a smaller amount per serving, the caffeine itself is different and may be tolerated less than coffee-based caffeine.
    For me, tea-sourced caffeine (which I believe is used heavily in Coke products, based on my own reaction) is much more poorly tolerated than naturally roasted and ground coffee. Even steeped tea will give me jitters and mental disconnects that I don’t get from coffee.
    Note that “herbal tea” is not actually tea at all. It is called “tea” because it is packaged and prepared in a manner similar to tea. Any real “tea” has caffeine.
    Green Tea does have caffeine, though it may be chemically different and therefore more tolerable than other teas.

  • Ted
Last Modified: August 30, 2016

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