Coffee is good for you—unless it’s not! | Chris Kresser
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Coffee is good for you—unless it’s not!

by Chris Kresser

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Numerous studies have linked drinking coffee with positive health effects like reduced risk of obesity, diabetes, and heart disease. However, recent research suggests that the effects of coffee on health aren’t the same for everyone, and may depend on genetics and other factors.

I love coffee—and I’m not alone.

Americans drink 400 million cups a day (yes, you read that correctly) and we spend $30 billion on it every year.

The good news is that there’s a lot of research that links drinking coffee with health benefits, including lower risk of cancer, Parkinson’s disease, obesity, diabetes, metabolic syndrome, and heart disease. I covered that research in detail in a recent podcast.

Here’s the bad news: while coffee is undoubtedly beneficial for some people, it may be harmful for others.

I talked about some of the factors, including sleep, stress, and intolerance to proteins in coffee beans, that determine individual response to coffee in another podcast a while back.

But there’s another important factor to consider: genotype.

Coffee is the primary source of caffeine for Americans. Caffeine is metabolized by an enzyme in the liver that is encoded for by the CYP1A2 gene. Unfortunately, about 50 percent of the population has a variant in the CYP1A2 gene that leads to slow processing of caffeine.

For these “slow metabolizers,” drinking coffee:

  • Is associated with a higher risk of heart disease (1)
  • Is associated with a higher risk of hypertension (2)
  • Is associated with impaired fasting glucose (3)
  • May not have the protective effects against some cancers that it appears to for “fast metabolizers” (45)

That said, in some cases coffee appears to be beneficial even for slow metabolizers. For example, caffeine is neuroprotective and reduces the risk of Parkinson’s disease in both slow and fast metabolizers. (6) Other studies have even shown that fast—not slow—metabolizers of caffeine may be at higher risk of bone loss. (7)

Is coffee good for you? That depends.

Adding to the confusion, many of the large, observational studies I reviewed in my podcasts found that the overall effect of coffee intake in the populations studied was positive. If 50 percent of people are at higher risk of disease from drinking coffee because of their genotype, then why isn’t this showing up in these epidemiological studies?

What are we to make of these conflicting data?

The most obvious conclusion is that it’s impossible to make a general statement about the health impacts of coffee. The answer to the question, “Is coffee good for me?” is: “It depends.”

This shouldn’t come as a surprise. If you’ve been following my work for any length of time, or you’ve read my book, you’ve probably heard me say, “There’s no one-size-fits-all approach when it comes to diet.”

The most recent research on nutrition, including these studies on coffee and caffeine, confirm that this is true. While we share a lot in common as human beings, we also have important differences: genes, gene expression, metabolic activity, gut microbiome, lifestyle, activity level, and numerous other factors will differ from person to person, and all of these will impact how we respond to a particular food (or beverage, like coffee).

For example:

  • There is wide variation in post-meal blood sugar among people eating identical meals, and diets that are personalized on the basis of dietary habits, physical activity, and gut microbiota are more successful than “standardized” diets. (8)
  • Response to low-carb and low-fat diets in overweight people varies considerably and may depend on their insulin sensitivity and other factors that are not yet fully understood. (9)
  • Caffeine consumed in the afternoon or evening significantly disrupts sleep in some people, but not in others. (10)

These studies represent the future of nutrition research. In fact, I’m quite sure that in a relatively short period of time we’ll consider the current notion that there’s a single, optimal diet for everyone as an outdated and ignorant idea.

Another conclusion that we might infer from the conflicting data on coffee is that even within a particular genotype the effects are variable. In other words, some slow metabolizers might be adversely affected by caffeine where others aren’t, and the opposite might be true for fast metabolizers. This also makes sense because there are a huge number of factors above and beyond the CYP1A2 genotype that would influence how coffee and caffeine affect an individual, from their baseline diet to their stress levels and sleep to their gut microbiota. It’s also true that being a fast or slow metabolizer of caffeine isn’t binary (i.e., two possible speeds: fast or slow), but more of a spectrum (ranging from very slow to very fast).

Now that we’ve established that coffee and caffeine can be both beneficial and harmful, how do you know how it affects you? Here’s what I suggest:

  1. Listen to my podcast called Is Drinking Coffee Good for You? in which I discuss some of the non-genetic factors that determine individual response to coffee.
  2. If you haven’t already done this, titrate yourself off coffee (reduce your consumption slowly until you’re off it completely) and other sources of caffeine for at least 30 days. Then add it back in and see how you respond.
  3. Find out whether you’re a “slow” or “fast” metabolizer. You can get this kind of genetic data through companies like 23andme and SmartDNA. If you’ve done 23andme, log in, go to “My account,” select “Browse raw data,” and type “CYP1A2” into the “Jump to a gene” search box. Once on the search results page, find the rs762551 SNP. In the far right column, it will give your variant of that SNP. If you are AA, you’re a fast metabolizer. If you are AC or CC, you’re a slow metabolizer (with CC being slower than AC).

We live in exciting times. At some point in the future, we’ll be able to create much more precise nutritional recommendations based on our genotype and epigenetic factors, in addition to all of the other factors I’ve discussed in my book—such as health status, lifestyle, physical activity, and goals.

Right now, we’re only scratching the surface and still have a lot to learn. But we already know enough to stop asking questions like “Is coffee (or carbohydrate, fat, etc.) healthy” and start asking questions like “Is coffee (or carbohydrate, fat, etc.) healthy for me?”

Now I’d like to hear from you. How do you respond to coffee and caffeine? Do you know whether you’re a fast or slow metabolizer? If not, what do you suspect? Let me know in the comments section.


Join the conversation

  1. Chris –
    You didn’t really get into whether we should use paper filters or no filters. My understanding is that paper filters remove the terpenes which give the cognitive boost but may raise LDL. Do we want to consume the terpenes or filter it out? Is it true that fats like MCT oil and butter help the terpenes cross the blood-brain barrier?

    Also, which roast is healthier: dark or light? From my research, I found dark roast coffee, such as French or Italian Roast, or roasts used to make espresso or Turkish coffee, are typically higher in neuroprotective agents. One study in Molecular Nutrition & Food Research ( found that dark roast coffee restored blood levels of the antioxidants vitamin E and glutathione more effectively than light roast coffee. The dark roast also led to a significant body weight reduction in pre-obese volunteers, whereas the lighter roast did not. Another study ( showed that dark roast coffee produces more of a chemical that helps prevent your stomach from producing excess acid, so darker roast coffee may be easier on your stomach than lighter roast coffee.

    So, is dark roast healthier?

    • What are your thoughts on Purity coffee? It seems to be one of the healthiest coffees on the market. They tested their beans against 49 other coffees, including Bulletproof coffee, and they were the highest in antioxidants and lowest in toxins. They apparently tested for 60 different mold toxins and contained zero detectable levels of these molds.

      If anyone is interested in testing Purity out, I used code EVOLVEDNS for 30 % off ($62 for the 5lb bag).

      I notice a difference in how I feel after drinking it (energy levels are very stable) and am able to drink it black. I’m wondering if it is because it’s higher quality or just placebo effect. Their decaf and pods are really good too.

  2. What about the non-dietary/ nutritional aspects of coffee?

    I ‘cured’ myself of my year-long daily GERD (severe reflux) through much trial and error, super strict diets (fish, hemp protein, sweet potatoes, olive oil, broccoli sprouts) … countless supplements, etc.

    What actually worked turned out to be a certain kind of probiotics (cough Garden of Life) – though I’m sure there are similar ones out there, just compare the strains on the back. At least I think that helped, who knows.

    Anyway back to coffee … that was one of the few consumables GUARANTEED to trigger my GERD back in the day (I can drink it fine now, though am trying to get off it again).

    Coffee was worse than alcohol, fried food, hot peppers (actually spicy/ capsaicin food had no effect despite common knowledge). My biggest triggers were coffee and refried beans (my GERD was related to intestinal gas somehow, either a cause or compounding symptom).

    It’s extremely acidic on the teeth and in the stomach in general. I can’t speak necessarily to throwing acidic food in the stomach, I’m not sure it would appreciably raise the actual pH of the large highly acidic stomach acid. In fact adding HCl digestive aids might help GERD in some cases. But coffee seemed to wreak havoc on my system when I was in this sick “GERD” state (I was never overweight either, oddly enough, that was not a cause — 6 feet 170).

    Now that I’m healthy, have rebalanced gut flora … coffee does not wreak any havoc, other than being a laxative of course. But it seems the potential is there. There seem to be some unique properties to coffee, moreso than just caffeine. Anyone susceptible to reflux is wise to steer very clear of it.

  3. I read this article ( and was inspired to quit drinking coffee after learning it is depleting the magnesium in my already magnesium deficient body. I can’t tell you enough the tremendous results I gained by avoiding this substance which does more harm than good.

  4. I think coffee doesn’t make a bad affect on me, or it may take a long time to see the result. Thank you for the post. For me, because I’m not a coffee lovers, but I will drink when I need to work and choose another drinks when I don’t need them.

  5. Very surprised to learn I’m a fast metabolizer. I wonder if that is related to my high sensitivity to medications? I usually need a much smaller dose than recommended for someone my age and size.

  6. Chris, you’ve talked about coffee quite a bit now but i don’t recall you mentioning the concern around mineral depletion and absorption, which is surprising considering how much you bang on about nutrient density and absorption.

  7. I think moderation is key. I know plenty of people who have become dependent on caffeine to make it through the day. It’s a bad idea to get your body to the point that it relies on a stimulant. Lucky for me, I despise the taste of coffee so I’ve never had to worry about it!

  8. I love coffee. It took me a year to get off of it when I was going through health coach training. Now I am back on and realizing I want back off. Tea is just not coffee, but my personality is very different on tea vs. coffee,,,,,,meaning tea= more calm, coffee= more frantic and energetic (which I like–I could build a pyramid). I CANNOT drink coffee in the late afternoon or evening or it will disrupt my sleep.! I love coffee and I hate it. (plus once I have a cup, I want another)!

  9. I have never been a coffee fan and honestly I don’t understand why so many people are addicted to it. I don’t mind having a cup occasionally, but what I’d really love is a cup of hot green tea with a spoon of honey! That has become my healthy addition.

  10. I tested as a fast caffeine metabolizer. If I drink late in the day, it does make me sleepy but not like alcohol. Alcohol knocks me out–best way for me to sleep. I can feel my glucose levels decrease whenever I drink coffee or eat chocolate. I don’t need coffee like other people, but I do occasionally drink it. For sure, I can feel its effects. I drink it for its taste and antioxidants, not for stimulant effect. Nikola Tesla considered stimulants including caffeine bad for your health, and he was extremely smart. It’s possible he was a slow caffeine metabolizer and could sense its effects.

  11. Hi Chris,
    Thanks for explaining how to check to see what category we fit into. I understand the caffeine is the kicker in this, but what about teas? How do they fit in with the coffee?

  12. Interesting topic. I went cold turkey and quit coffee in 2012. I was drinking 2 to 3 cups of coffee daily with a lot of added milk and sugar, which increased my weight. I was also drinking at least 2 Diet Cokes daily which combined with the coffee would sometimes make me jittery. Caffeine can affect your central nervous system over time.

  13. Chris,
    Very interesting, as always! When you sent your genetic data to your friend, I hope she sent it back! I’d hate to lose that. 😉

    As for my coffee habits, I seem to be just like you – really sensitive. I backed it off to just one cup per day in the morning, made in a nice vacuum pot. If I have a cup past 3PM, I may be in for it.

    I know someone who absolutely insisted on drinking coffee right up to bedtime. She did indeed fall asleep, but in her chair, and would wake up repeatedly through the night, and wouldn’t have the strength (or lucidity) to actually get to bed. I explained that cutting out the coffee may greatly benefit her sleep, She shut that conversation down right quick. Oh well.


  14. Hi Chris,
    Thank you for show us this research tool for 23 and me. When I looked at my “caffeine consumption report” on 23andme it states that I am more likely to consume more caffeine than others (9 mg more). How is this possible if I am a slow metabolizer (my results showed C/C). Wouldn’t someone who metabolizes caffeine slowly tend to drink less than the average person? I drink mostly Swiss water processed decaf now b/c regular consumption left me with headaches when I didn’t drink it daily and then monthly migraines around my period. It seems like the caffeine report contradicts what my gene variant data shows.

    Also, to get to the report you go under Tools, then scroll down to browse Raw Data. There isn’t a my account tab anymore.

  15. A word of caution about coffee. I don’t have the references to hand any more but when I was researching neuroprotective agents last year I found many articles through Google Scholar which made it clear that, although neuroprotective for men, coffee consumption was not so for women – quite the contrary in fact – at least post-menopause. Worth checking.
    For myself, I love everything about coffee but sadly it doesn’t love me. Incidentally, when I was pregnant the smell alone would make me feel quite ill. Worth listening to your body I think!

    • Oh wow, me too! That is how I always knew I was pregnant. I love coffee and I am down to one cup a day, I drink only organic. Anything over that 1 cup and I feel terrible for hours. I know I need to get off it but I have to have sharp focus at work. Retirement is coming soon so I think then I can get rid of it then.

  16. I live on coffee some days having 6 cups I have not done any genotyping but was wondering am I a fast coffee metabolizer since the caffeine does not affect me or keep me awake at nights. I can drink a cup of coffee and go to bed and have no affect on my sleep.

  17. Hello Chris,

    Great article! I am writing on behalf of FitnessGenes and we test individuals for the caffeine metabolizing gene you have mentioned in your article (rs762551 SNP, the same as 23andMe). As you have mentioned, individuals can be separated into those who carry ‘fast’ and ‘slow’ caffeine metabolizing genes.

    At FitnessGenes, we also agree with your statement that fast and slow caffeine metabolism speeds are more likely to be on a spectrum than just two speeds. This is because we have found, when doing our research, that caffeine metabolism in fast metabolizers is inducible. That is, someone with the AA genotype may only start to metabolize significantly faster than someone with AC or CC if;

    They live in a polluted area (air pollution)
    They drink more than 3 cups of coffee a day
    They smoke
    They eat lots of leafy, green vegetables.

    Interestingly, the studies we reviewed showed this but also showed that eating lots of leafy green vegetables increased the speed of caffeine metabolism for both AC and CC individuals too! This is probably why there are some individuals who are AA who feel they are slow and maybe some who are AC and CC who feel they are fast or unaffected by caffeine (some allude to this in your comments section).
    We give our customers this information with quoted studies. The diseases you have mentioned (heart disease, hypertension, impaired fasting glucose, cancer) can be caused by a wide combination of both genetic and lifestyle factors which makes some studies on caffeine metabolism and disease risk hard to disentangle. Also, FitnessGenes is a fitness DNA testing company, we do not advise on disease risks, and we focus primarily on fitness advice designed to get people into the best shape of their lives!!

    Feel free to get in touch to find out more!

    Dr Dan Reardon, CEO of FitnessGenes

    • Any specifics on the greens or reasons for it? Any links to the studies that back up those conclusions? Love to read about it in detail.

  18. Hi Chris,

    Thanks for all the wonderful things you do!

    Started the diet 5 months ago and have lost 43 lbs. and have never felt better.

    Regarding the coffee issue, I used to practically pass out 10 minutes after I had a cup. I cut out coffee completely for the diet. Now I’ve reintroduced it and have no ill effects. I realized when I Used to have coffee I’d always have it with a teaspoon of raw sugar.

    I can drink coffee now without feeling jazzed up or passing out, and I think it’s because the sugar gave me all those ill effects, not the coffee necessarily. So when someone is trying to determine what effect coffee has on them, maybe they should have it black, without cream or sugar. It may not be the coffee, but what you put in it, that’s the problem.


    Very Best,


  19. Hey Chris,

    I’ve been a coffee drinker my whole life. My family is Portuguese and we sure love our coffee! Over the last two years, however, I noticed that I would get chest pain on the left side all day. Sudden little jabs that would take my breath away. Anyway, a friend of mine was telling me that his friend drank too many coffees and landed up in hospital, thinking he’d had a heart attack, so I decided to switch to organic Swiss water decaf (because I love the taste so much). The chest pain went away after I made this change. I occasionally get the decaf mixed up with my husband’s coffee and if I do this more than once in a row, the pain returns. It’s very strange, considering I was quite fine with coffee for so many years beforehand.

  20. It’s not only how you metabolize coffee, it can be the long term effects you experience. I’ve never been a big coffee drinker but I had been using it for several months when I noticed I didn’t have the energy I use to have. I stopped drinking coffee and about a week later I was back to normal. I don’t believe the hype about how good it might be. I think there is a lot a marketing going on with it.

    • I so agree on the marketing hype around so many “food substances” that are supposed to be good for us. Hype sells when the food is raised to a “superfood” level.

      I never have been a coffee drinker (as I do not tolerate caffeine well) and then at 45 or so started drinking occasionally with my partner. Little by little it became a daily habit. I found myself suffering from low level muscle, bone, joint, (all over body aches), low energy, and a host of other ill symptoms that made me wonder about Lyme disease, rheumatoid arthritis, etc.

      Stopped coffee and all is fine again.

      Slow metabolizers of caffeine are creating a back up of toxins in the body when they use caffeine regularly. The liver can only detox so much before it gets over loaded. Toxins in the system make for ill health symptoms.

      Some people thrive on a coffee, others do best avoiding it.

  21. Serious question: I drank five cups of coffee yesterday afternoon, last one about 5pm. Worked till 9pm, then watched some tube. Went to bed at 11pm and slept like a baby. Can I reasonably infer that I’m not a slow metabolizer? I kinda hate the thought of weaning myself off for a month, if I’m not having any issues.

  22. I have avoided coffee for most of my life, but this summer on holiday in France, I started drinking a couple of cups every day (black, organic, strong). At the end of the holiday, I noticed that I had broken out in tiny little spots and ‘potential’ spots (ie, bumps) all over my chin. This is at the age of 43 when I’ve always had lovely clear skin.

    When we came back, my husband and I did the 14Four, so no coffee there, but I reintroduced it after the two weeks. Spots got worse.

    I searched the internet to find out whether coffee might be the culprit and came across this article, which seemed to indicate that it might well be.

    Since then I’ve cut back to one cup on a Sunday and the spots do seem to be slowly fading away.

    The whole episode slightly freaked me out as I have never had any issues with my skin at all, and it really knocked my confidence to start breaking out in spots at my age!

    The only other possible culprit might have been sudden high levels of animal fat in my food. In France, we ate lots of pate etc, and then we came back and did the 14Four with lots of traditional cooking fats.

    We’ve since moved to more coconut oil and less goose fat …

    I’d love to know if anyone else has found a connection between coffee and skin problems.

    • This was a long time ago but I thought I would share. I too have great skin. When I was in High school, I started getting pimples and my older co-worker told me to drink nothing but water for 2 weeks (I was drinking Pepsi). Pimples were gone and I was hooked on water. About 4 months ago I started drinking 1 cup of coffee in mornings, I noticed my skin does not look as good. I’m finishing up my last cup of ground coffee and plan on getting to bed earlier and drink homemade bone broth instead. Collagen in broth will probably be better for my skin than caffeine. Good luck!

  23. Hello Chris, thanks for the article. My mother had Parkinson, so wanted to make sure, as written in the article, that I will benefit from the caffeine, not from decaf. also, what is the minimum effective amount? I am probably a slow metabolizer, as caffeine keeps me awake for many hours. I was off coffee for about 6 months, not sure I can determine the effects on me. Thank you!

  24. I love coffee, not only the taste, but the relaxing feeling I get and the way it does away with the slight nausea I get when I wake up in the morning. However, here is the bad part: after a couple of hours, I get horrible heartburn and even acid reflux. It isn’t only coffee that gives me heartburn — so does meat and the very worst is red wine, followed by white wine, which l\hit my stomach like battery acid! This started about 5 years ago, and with every passing year something else is added to the list. Poultry, for example. Fish, so far, is fine. Acid vegetables like tomatoes and sour fruits cause instant pain. What, if anything, does coffee have in common with these things?

    • Hi Esther,

      Coffee is acidic as well, so that might be what’s common among these foods. Red wine is also quite acidic, while white wine is somewhat less. Do you also drink black tea? If you do and the effects are similar, that’s probably the reason. Maybe you could try to drink your coffee with some fats, cream if you tolerate it, or with coconut milk, coconut oil, or ghee.

  25. I love coffee! But I do not love caffeine- it makes me “bouncing off the wall” jittery! I am looking forward to my next cup of rich, dark DECAF coffee… unfortunately it will be a long while before I can have it, as I am struggling with Candida and adrenal fatigue. Still love the smell when I brew it for my family.

  26. My love affair with coffee has taken a dive over the past 12 months. I backed right off from 1-2/day to 1-2/week in response to fatigue problems and found that it negatively affects my mood. I get “blood boiling” angry, flipping out at the most trivial things. Its like my body can’t handle the stress that the coffee seems to put me under. It only seems to have become a problem since having fatigue issues. I’m not sure if its the coffee, caffeine or both.

  27. The bottom line for me is how I feel or intuitively expect to feel from any food or beverage. If it supports me I consume it, if not I don’t. I prefer not to dwell on the science and theories, only the results.

    Science is great when it is accurate 100% of the time. Unfortunately this is rarely the case so it can only be used as a guide.


    • That is good advice. That’s how people found out what to eat in the first place. The way we are made to operate. We should be in the woods too and we’ve lost so much common sense.

  28. I hope people are hearing you and perhaps also thinking that their animals don’t have one-size-fits all nutritional needs. Our animal friends need us to create the best and most personalized nutrition for them. We have fed our dogs, cats and horses custom, fresh, organic, homemade diets for years and they live a long time with very few health issues. Thanks Chris for your great work!

    • What do you feed your cats? I want to cook for mine but am unsure how to do it. I tried once and the meat was too dry I think and he would only eat some of the juice.

  29. Great article! I think I’m one of the sensitive ones as well. If you are still wanting to get the benefits of coffee, check out the supplement EHT on my website!

  30. Always great to read your stuff, first class info, that is so profound ,yet simple to understand ,thank u so much for being such a great educator with real heart integrity,,,keep in on

  31. i’ve never liked coffee much, then 5/6 years ago i gave up all tea and coffee and only drank herb tea due to liver issues that were bettered, i think , mostly by cutting out sugar.
    a few months ago i had some coffee to stave of an impending migraine.
    i did this a few more times and since have become someone who enjoys coffee every day.
    i used to get a huge buzz, not so much anymore.
    it#s a really weird development but as i believe in going with my body’s cravings/intuition i am quite comfortable.
    it seems to help with my tendency to headaches/migraines and somewhat with my fibro fatigue.

  32. It is an interesting subject, coffee! This has been my experience. Whenever I drank regular caffeinated coffee, and then tried stopping, I would always get a “detox” effect of headaches and a general sick feeling for at least a day. So I decided to go decaf and not worry about “running out” of caffeinated coffee. This is the interesting part for me, when I went organic, and began drinking “organic” regular french roast coffee (strong), when I ran out of it, I DIDN’T have a “detox” reaction or sick day. In fact, nothing happened. I was so taken by this, I ran out a few times more, just to see, and nope, no “sick day” of any kind. So, I also have to ask, is the food in question grown organically or not now. Then, go from there. Of course, caffeine is caffeine, so, not sure what different effect it would have. I don’t “jump off the walls” after regular coffee. I could actually have it at night and sleep. But, then it’s “organic” so, really, I can’t say. Anyway, something else to add to the problem I guess 🙂

    • Coffee can be highly sprayed with pesticides, and it can get mold if not kept properly. I think you are right. Organic is the only way to go. Weirdly I find espresso at a good coffee shop makes me feel well as opposed to drip coffee anywhere else. Of course that’s not organic, but I’ve never seen organic sold at a cafe, just the beans you can make at home.

  33. This was fascinating! I’d love to get some of that testing done and find out whether I’m a fast or slow metabolizer.

    I’m particularly interested in the effect of coffee on migraines–any good info on that? I think too much coffee may be a trigger for me overall, but when I already have a migraine an extra cup seems to make it go away faster.

    Over the past four months I’ve reduced my coffee from 3 large mugs per day to 1 actual 8-ounce cup per day. I’m sleeping better and I lost some weight without really trying, which usually happens when I reduce or give up coffee. In the past when I’ve given it up entirely I’ve switched to green tea, but now I’m contemplating giving up all caffeine for 30 days and seeing how it goes…

  34. On top of the above issues mentioned, another spanner in the works here is for those of us who have been severely injured by fluoroquinolone antibiotics, & now suffer from what is commonly known as fluoroquinolone toxicity.
    Fluoroquinolone antibiotics ( Cipro , Levaquin Avelox etc ) inhibit the liver P450 enzyme pathway to varying degrees, the enzymes used to metabolise caffeine, therefore coffee ( & also the majority of drugs which enter the body ). This inhibition by fluoroquinolone antibiotics lasts for varying amounts of time & the timeline seems somewhat dependent on the severity of reaction.

    Having been severely damaged myself, prescribed these so called antibiotics many times before I realised what had really happened to me & why I was so very unwell, I now find I can no longer tolerate coffee at all, even in the smallest amounts. Coffee in any amount makes me feel extremely ill.
    For those of us who have been injured by these DNA mitochondrial damaging chemo drugs that masquerade as antibiotics, ( a situation known as floxed ) this is unfortunately a very common scenario.

    Many of us who are injured by fluoroquinolone ‘antibiotics ‘, find we now have another issue, as well as being intolerant to caffeine we often find we are also unable to tolerate various allopathic drugs, both those we might have taken with no noticeable problems whatsoever in the past before we were hit, & many of us also are finding the same issues with various allopathic drugs we might have no choice but to take in the future, depending on our own personal situation, the genetic implications etc as mentioned above etc, & on how the particular drug prescribed is metabolised.
    I personally have been in this situation for many years & I do often wonder if these enzymes will ever fully recover in my case, as I have not been able to tolerate any allopathic drug I have been prescribed since my most severe reaction, including other classes of antibiotics, I try very hard indeed now to avoid allopathic drugs when humanely possible.

  35. I am very sensitive to coffee, and even one cup in the morning can keep me wired all day, and have trouble sleeping that night. I think this may be atleast partly to do with having fibromyalgia, which apparently makes my nervous system very sensitive already. My mum has recently stopped drinking caffeine, and she’s says it must have been slowly ‘poisoning’ her for years, as she has double the physical energy now and much better wellbeing. So maybe my sensitivity is genetic too. I actually am using coffee ATM though to alter my sleep pattern, as due to my chronic fatigue, I go to bed at 6pm, which causes problems with night eating and early waking. So I’m drinking a cup of coffee now in the mornings to try to stay awake later. Thank you for these excellent articles.

  36. Chris, have you heard of Your article could have been a advertisement for that program. I’d love to have you do an article or podcast about it. I don’t think it’s all 100% correct, but it’s definitely the future of diet and overall health.


  37. Coffee has almost no effect on me. I drink a couple of strong cups every morning, and sometimes another in the afternoon, and my husband and I drink espresso every night after dinner, never with any problem sleeping. Also, if I drink coffee in the afternoon I can immediately lay down and take a nap… No effect! I just like the taste, especially with heavy cream!!!! Must be a very fast metabolizer. I do notice that I always have to pee exactly three times within an hour of my coffee in the morning!

    • It does not mean that you are necessarily a fast metabolizer of caffeine. You may simply have developed a caffeine tolerance, i.e. your brain is not reacting to caffeine. However, silently, the caffeine may attack your heart and the damage may be slowly accumulating until it will show up later in life. This happened to me. I used to drink a lot of coffee like you without having a problem and without knowing that I am a slow metabolizer (CC genotype). At the very beginning of drinking coffee I felt some stronger heartbeat but did not pay attention too much. Continuing drinking coffee it disappeared but returned after my 50! One can not be sure without the genetic test results. If I knew before, I would certainly avoid drinking too much coffee if any…

    • Coffee is a diuretic and can also have a laxative effect. It’s always recommended to drink water after having coffee. Most cafes in France and Italy serve espresso with a glass of water 🙂 – how considerate!

  38. I recently switched to tea – green, oolong or black. I find tea to be very different from coffee not only in terms of caffeine content but also in terms of the quality of the stimulating effect. Apparently there are some components in tea like theobromine and L-theanine that work synergistically with caffeine and create a more balanced buzz without the jitters. A kind of alert relaxation.
    I’m in a process of healing my adrenals and tea works great for me right now.
    I wrote more about it here:

  39. I am definitely a slow processor of coffee. I had never been a coffee drinker until a few yeas ago. When I consistently drink coffee every day this is what I notice: sleep disturbances, blood sugar and digestive upset, muscle / bone / joint aches (truly I wake up every day feeling like every cell in my body aches), and poor exercise recovery time (a 1 1/2 hour yoga class would leave my body seriously aching for 4-5 days and I have been doing yoga for 16 years). I stop coffee and it all ends.

    Bummer I say as a hot cup of coffee with lots of full fat (pasture raised) goat’s milk is a delightfully creamy way to start the day.

    I have tried all of the coffee substitutes, and many are yummy, but they do not taste like coffee.

  40. Chris, you talk about ‘slow metabolizer’ of coffee; if one is AC or CC does this make them a slow matabolizer in general? E.g., metabolize food slowly, difficult to lose weight, slow to move, etc? Thanks!

    • The metabolism of caffeine happens in the liver and it’s the detoxifcation of that caffeine that we’re talking about when we say “caffeine metabolism”. So if the detoxification process is slow, we say someone has slow caffeine metabolism. Having fast or slow caffeine metabolism does not mean someone will have fast or slow metabolism in general.

  41. I am an ‘ultra fast metabolizer’ according to my genetic data. Accordingly, I can drink a cup and fall asleep instantly. Currently I am only drinking tea, as the acidity of coffee bothers me. 2 cups green tea, 2 cups black during the day. I have been off of caffeine for long periods due to HPA axis issues, but I generally feel better on it.

  42. 23 and Me results show that I am a slow metabolizer of coffee. It has been so hard for me to give up my morning cup because I enjoy it so much. I sometimes get sick due to the acid on my stomach. It is part of my morning time to myself. I tried to replace it with green tea which is beneficial for my O blood type but I am allergic to green tea. Also allergic to red wine! Try to limit myself to one cup. Eat mostly a Paleo diet. My results also showed that a low fat diet would make me fat. I followed a low fat diet for almost 20 years. I was a skinny fat. Now with Paleo diet I have noticeably less fat. My husband is blood type A and a fast metabolizer. A low fat diet with vegetable protein benefits him. It was our 23 and me results that led us to realize there is an individual diet for everyone. I believe the day will come where each person can get an individual diet for their optimal health. It will be their decision to follow it!

  43. I’m sure I’m in the “fast” category – I am always a good sleeper and can drink a cup after dinner without if bothering me…pretty much got off of coffee with my “reset” month – am happy to have coffee back in my life?

  44. I stopped drinking coffee when i was studying for my final exams in high school (1984). While studying, i switched to eating more fruit and felt better. I didn’t really go back to drinking much of it after that. However, years later (in my 30s), i developed insomnia – lots of stress – and one day i had a cup of coffee. My heart starting beating so wildly i thought i was going to have a heart attack!. I remember having that coffee some time in the early hours of the afternoon, but i still couldn’t sleep at all that night. The only time that coffee hasn’t effected me since then is when i drank a couple of cups of decaffeinated organic coffee made locally in Melbourne, Australia. In the past i tried decaf, but had pretty similar effects to regular coffee. This organic brand tasted so mild and delicious i simply couldn’t stop at one, and I didn’t care about the lack of sleep it was going to bring me. To my surprise, i had no effects whatsoever. I didn’t push my luck – i stopped there, but will try it again out of curiosity – one day in the near future.

  45. I have become somewhat desensitized to caffeine. Even tea after 2:00PM used to keep me awake. Now its just if I have sugar with the coffee. Since I’ve started to spike my coffee with
    coconut oil and some protein powder, I notice that the jitters are gone.

  46. I was one of those people who had no problem with caffeine: coffee in the morning, lots of black tea during the day, and chocolate at night. About a year ago, I did Chris’s 30 day reset and then went on a moderately low carb paleo regimen, on which I feel great and have lost weight. But a few months in, I developed a severe reaction to caffeine. Once cup of coffee and half and hour later my heart pounds and misses beats. It’s scary! I was wondering if going off a low-fat, high-carb diet and onto a paleo one, can affect caffeine tolerance? Has anyone else had this experience?

  47. I’ve never drunk coffee in my life – can’t stand the taste or the smell. Especially, I can’t tolerate standing next to someone with coffee breath. However, I used to drink iced tea (I’m from the South) all day. I can’t/don’t do that any more because even tea now makes me jittery to the point that I feel as though I’m having panic attacks. Chocolate makes my stomach hurt and I love it – I just allow myself one little piece once in a while knowing that I will just spit it out – not worth the discomfort but I still get the taste. Strange, huh?

  48. That’s odd. It turns out I’m AA and yet I have been off coffee tea and anything else caffeinated for most of my life because it affected me so much. This makes no sense yo me at all.

  49. I’m following an autoimmune protocol but LOVE coffee and think it is my only true vice, in that I find it very difficult to completely eliminate from my diet. Eliminating grains, legumes, dairy, and greatly reducing sugar has been much easier than trying to manage my coffee craving. I allow myself one black coffee a day, and never past 2pm as I know even that will have me awake til midnight. I used to find I ‘burned out’ on coffee and would become emotional and jittery. I’ve found supplementing with a good quality magnesium has helped enormously with this.

  50. I have been diagnosed ADHD (suspect it’s actually ASD though), and appear to metabolize caffeine and even medicines quickly! I used to go grab a 20 oz coffee at 9 pm (I worked days, and started work at 8 am), and would have people ask if I planned on sleeping. I was, for a long time, curious why they would say that! I would head home and hit the hay at 11 pm and fall asleep before my head hit the pillow. Great sleep all night too. I’m trying to not use it now because I think I may have adrenal problems. I miss it though. I noticed I do have a problem with sleeping with alcohol though. Wine make me wake up a lot when it leaves my system.

  51. I gave up caffeine about 4 months ago and after 5 days of awful headaches started to feel so much calmer, my menopausal flashes and night sweats have disappeared, except for slight flashes if i eat too much chocolate. Never really tolerated it well but got less tolerant after my hypothyroidism diagnosis at age 29 and even less tolerant when diagnosed with type 1 diabetes at age 36. I will never consume caffeine on a regular basis again as I am feeling so chilled but energetic at the same time and no more frightening palpitations

  52. I love coffee, and I love caffeine. I must be a fast metabolizer because it doesn’t disrupt my sleep even if I drink it in the evening. However, I did give up coffee (VERY gradually) this year because of a positive IgG ELISA test. I realize this test is controversial, but I figured it would not hurt to give it up for 2 reasons: (1) possible weak adrenals, and (2) I become so highly dependent on caffeine that I will get a severe headache if I don’t get my fix.

  53. Do you think it is possible for coffee compounds and/or caffeine to cause elevated CPK (muscle breakdown) in certain individuals?

    I read this book last year “Welcome to the Dance: Caffeine Allergy – A Masked Cerebral Allergy and Progressive Toxic Dementia” in which author Ruth Whalen discusses her experience with unexplained health issues (Physical and Mental) including elevated CPK and ultimately links it back to coffee/Caffeine consumption.

    I too have had labs with slightly elevated CPK levels for unknown cause that seem to return closer to normal when decreasing caffeine. I can’t find too much other information to support this online.

    I am a slow metabolizer and have found discussions on caffeine’s negative effects on sleep and anxiety but not much related to the idea of caffeine/coffee compounds causing a cumulative toxic effect overtime that could induce CPK muscle breakdown and other psychosis systems in susceptible individuals.

    Thanks for another great article Chris!

    • i am addicted to caffeine and it raises my blood pressure and swells my legs and eyes as well as making me more hungry. However I dont want to get out of bed without it so I struggle. Once off coffee and its a 5 day of depressions to do it I feel better but so calm I could put myself to sleep any hour of the day in 3 minutes. Not a useful way to live. Week adrenals and metabolic syndrome is encouraging me to give it up . I am a slow metabolizer and methylator as my liver considers it toxic . So why did I have it today ?
      Perhaps not tomorrow

  54. This is a little bit off topic, but I’m one of those people who has a problem with the protein in coffee so I had to give it up. But I’m wondering, what about coffee enemas? I mean, do you absorb any protein from that or does it somehow get into your system? I realize your colon isn’t your gut, but you do absorb thru your colon. Coffee enemas are on the Gershon protocol for liver detox and every time I’ve done them, I feel really bad afterwards.

    • I just came across this and am wondering if u ever found an answer, and if u would mind sharing some links if u did. I too would like to know about coffee enemas. According to my DNA I don’t do well with coffee, and when I do coffee enemas I don’t really feel a difference. I have a friend who can’t function w/o coffee enemas and my mom says they make her feel so much better! I’m wondering if the genetic thing is what makes the difference!? BTW: my mom doesn’t have the gene for it (so I must get it from my dad). Thanks!

  55. I have always known that I can’t ‘handle’ caffeine. Most recently, I had a pot of white tea (2 cups) at 3pm and was awake with a pounding heart until after midnight. 23andme confirms: I have the CC variant of the gene in question! So cool. My husband can’t handle caffeine either, so I’ll be warning my children away from it.

  56. After I got my 23 and me test done, it validated what I had already assumed on my own…

    Which is that I have the genetic mutation where I metabolize caffeine very slowly. There are some of my clients that metabolize caffeine so slow, they could have a cup at 6am and still have trouble sleeping 18 hours later.

    It’s a double-edged sword that’s really not worth it…

    Despite the antioxidant effect, it’s caffeine…

    It wears out the adrenals and contributes to adrenal fatigue. I’ve seen enough adrenal profiles to make the correlation.

    Try Matcha tea since it has the perfect balance of caffeine and L-Theanine to calm the nervous system by supporting GABA levels.

    • I LOVE matcha. Depending on the brand, variety, it has a wonderful soothing alert yet calming affect for me. Since I have adrenal issues from stress it will continue to be an occasional treat.

  57. Thanks for showing us how to find the answer to that, Chris! Caffeine has never given me that extra burst of energy like it does for others. I remember in college, I would drink triple lattes to stay awake in class and I would still end up falling asleep! My results show that I’m A/A. I can drink coffee at night and still fall asleep without a problem.

    • Falling asleep after triple latte’s as an AA fast metabolizer says more about adrenal overwhelm followed by exhaustion (little adrenal reserve at that time) than fast metabolizer genetics.
      Cortisol may have even been perfect (or not), but when stressed by the brewed coffee etc, adrenals may have become overwhelmed and temporarily “crashed.”

  58. No caffeine after 1 PM and no chocolate after 6. Prefer dark roast . The larger issue for me is to drink organic or I get a stomach ache. Am a celiac on a cnsistent gf diet for 11 years with other sensitivities. Even non organic GF processed food can be a problem. Caffeine became better tolerated after eliminating gluten and all non-organic processed food that stressed my digestion and body. I am very thankful for your functional health info. 81 yo and this info helps to comfortably maintain the body I live in. Blessings from your work and on your work! JBH

  59. Now that I think about it the bags under my eyes that I get from drinking coffee are not from the proteins because I did not test positive on the Cyrex test for cross reactivity to gluten(and I am highly gluten sensitive. Even when I drink cold brewed, organic, swiss water de-caf I still get the bags under my eyes, sometimes even worse from the cold brew, actually.

  60. Interesting article! I don’t handle coffee well as much as id like to believe I do. On top of the fact that it makes me jittery and ravenously hungry, it completely disrupts my gerd and acid reflux (not immediately by the way… If I drink coffee in the am I’m plagued with acid reflux in the late afternoon). For some people you don’t need DNA testing to prove that coffee isn’t good for you!

  61. Being in London I don’t think I will be able to check my type but I do enjoy two mugs of organic coffee each morning with no other caffeine for the rest of the day. I have stopped using coffee but love the smell and don’t feel better without it. Six months ago I gave up milk products and drinking black coffee really makes me aware the taste, this is definitely linked to the quality.

  62. I don’t know the type of metabolizer I am, but coffee works for me very well. On workdays I take two full cups (strong, but not expresso-strong) in the morning, on weekends one.
    I have also experimented with not taking it for a while and don’t get withdrawal symptoms like some people.

    It is pm now here in the office, not my usual time for coffee but after i do this post I am going to make coffee, this conversation has made me do it!

    For me coffee is like the spice in Dune!

  63. I checked DNA data and I am a fast metabolizer. That’s good news:)

    But coffee has been very problematic for me for other reasons. My digestion is upset easily by drinking it (whether it’s caffeinated or decaf). I often end up with diarrhea after drinking coffee, especially on an empty stomach. I believe it’s got a very complex chemical profile so I could be reacting adversely to any number of compounds in it.

    I do love it…and appreciate the stimulating “boost” I get from it. But I have to be very careful in the frequency and amount I drink.

    • I get a bad case of diarrhea after even one cup of fairly weak coffee. I assume this is an allergy or intolerance to one of the many chemical compounds in coffee.

  64. If I have any coffee or tea, even decaf – I will not sleep that night. I may fall asleep for a few hours but I will wake up at 1 or so and that will be it for the night. I also have high blood pressure, so coffee is just not my cup of tea. 😉

  65. I have been diagnosed as suffering from acid reflux. Apparently this condition is extremely common. The symptons for me are hoarse and tired voice and occasional swallowing problems. My doctors and the NHS website state that coffee is a major factor in encouraging acid reflux and have advocated giving it up as a life style change to combat my problem without resorting to the standard anti acid medications. Decaff is apparently just as bad as non decaffinated.

  66. I love coffee BUT! If I have coffee one day my body needs it the next day to get started. Presently I have been off coffee since May as part of an allergy elimination program. Had it one time recently against my intuition and my body did not like it.

    I wonder about the affect of the roasted oils? I find with nuts I can have many types of raw nuts but do not do well with the same nuts roasted. Wonder if it might be the same issue with roasted coffee beans. Of course I do not drink the beans raw so will not find out unless; I wonder if the beans raw in another form ground into raw food would provide a smoother caffeine benefit.

  67. I barely, rarely ever feel the effects of caffeine. No matter the source. I have to be on a fast of some sort to feel the slightest buzz. Drinking it is more ritual and comfort then for the lift.

  68. I don’t know if I’m a fast or slow metabolizer, but I am definitely a non-responder. Caffeine does not keep me awake. When I was a security guard I drank red bull and ate chocolate covered coffee beans and thought to myself, “Is this even doing anything? Because this stuff tastes like cat wee.” For a while I had to get up every morning for 7 AM, which is NOT what I like to do, so I was drinking coffee like water. It wasn’t helpful.

    Now, I can drink four pot-cups – two real cups – then take a nap. I don’t drink past 4 just in case it disrupts my sleep, but when I go to a restaurant and have coffee with the dessert, it seems to have no effect on me later. So yeah… no real response at all as far as I can tell.

  69. Great topic Chris, thanks for going into depth on this. I am AA, (a fast metabolizer of Caffeine), but also carry poor copies of COMT…so while the caffeine doesn’t bother me…the excess catecholamine release does and so I’m still sensitive to excessive caffeine indirectly.

    • I’m rs762551 SNP AA too. Reading your reply makes me curious about the COMT catecholamine connection. Can you please point me to more information about that? Thank you. What do you mean “poor copies”?

      The recent CK podcast with Ben Lynch and the reference to PEMT and GAMT got me digging around in some of my results wherein a came across a reference to bananas and citrus (and vanilla) also triggering catecholamine release. Did not know that. Trying to piece things together.

      • COMT SnP’s (cause slowed COMT actiivty, not necessarily a “bad copy” as I introduced it) keeps your catecholamines in your system longer. (example norepinephrine/epinephrine/dopamine), It can be a good thing when it comes to focus and so forth, but it can be a bad thing when it comes to anxiousness, addictive tendencies, OCD, etc. So the coffee leads to extra norepinephrine/epinephrine release…and so even though the caffeine gets processed for me…the other hormone stay around and I get anxious and irritable – made worse if you’re adrenal fatigued in the first place.

        You can have poor synthesis, but you can also have poor degradation too…which copper is involved with.

        This is why I feel it’s important to do Organic Acids with your genetics so you know what’s active for you at this moment, as opposed to what is “potentially” active based on your genetics. With just genetic information you can think you should be on 20 different supplements…but you take the organic acid testing and the rest of your history, and you may realize that out of the 20 potential supplements, 3-5 of them may give you 80% of the results.

    • On COMT genetics in relation to catecholamine neurotransmitters and coffee, COMT homozygous variants (that have the effect of keeping catecholamines and to some extent estrogen in in the system 3-4x longer than wildtype genetics) may not result in high catecholamines (and estrogen) if synthesis of these is poor. Synthesis of catecholamines and estrogen can be seen through genetics but need to be cross-referenced to functional testing as complementary.

      I too carry the COMT homozygous variants across all key COMT snp’s, but my dopamine and estrogen are low due to low synthesis, so COMT helps me by keeping what little I have in the system longer. Too often it’s automatically assumed that COMT homozygous variants result in high catecholamines — not necessarily!

  70. This is interesting…I have had a somewhat paradoxical reaction to caffeine for several years now. My eyes get incredibly tired, I can’t breath, yet I feel anxious and wired internally. Can you explain the possible physiology behind this?

  71. Very interesting. I looked it up an I’m CC. I love coffee but did quit for 8 months and felt great. I started drinking it again in June and now I’m tired all the time, I get angry more easily, my skin is wrinklier and my thyroid antibodies that had gone down from > 1000 to 500 have gone back up to 800. So it’s clear that coffee isn’t good for me. Guess I have to quit again.

    • Yes, I’m with ya. It appears I metabolize it quickly, but it doesn’t make my gut feel well over time. Bloating and bladder issues come along with it. I’ve taken it out for about 6 months and discovered this. And then a few weeks at a time during other “experiments”. So sad.

  72. Coffee does not seem to have any noticeable effects as long as I don’t drink it later in the day. And I do like a bit of half & half plus some sugar in it as well.

    For while I did 3 cups. Now, I rarely go over two 8 oz. cups.

  73. Coffee makes me feel slightly nauseous if I have more than 1 – 2 cups per day. It also makes my neck ache for 4 days. I used to drink coffee once or twice per week – which meant my neck hurt all the time. It took four days for the pain to go away. I’ve never drunk coffee since I figured that out.

    Coffee also causes headaches in lots of people – I’ve had quite a few clients whose headaches have stopped when they stopped drinking coffee.

  74. In the last six months my LDL has increased from 101 to 154. That is when I started drinking coffee. I have factor 5 and hypothyroidism as well. I find it odd that my LDL has increased since i started drinking coffee. I have normally 1 cup a day during the week and 2 cups a day on the weekends.

  75. I am A/C on 23&me a slow metabolizer. If I drink regular coffee it upsets my gut. Espresso is fine as it has less acid. I drink 3/4 decaf shot of espresso and get lots of energy for several hours. I have to be homeopathic about it and do this not every day. I guess given I’m a slow metabolizer that’s why a mostly decaf shot gives me such a boost. I’m about to try bulletproof again making it with mostly decaf and small amount of caff to see if the “crash” coming down part is easier. It’s hard to resist the energy boost. I didn’t drink coffee for 10 years before I found this formula that works for me

  76. Does anyone else get nighttime leg cramps from coffee and/or chocolate? I can generate cramps by consuming these things, especially if I take them in the evening, and can stop the cramps by going off them. The more nice, dark chocolate I eat, the worse the cramps. Just curious, as I have found little mention anywhere that others experience this cramping from chocolate or coffee. I have recently learned that I am a ‘slow metabolizer’ of caffeine.

    • I would guess your body is not getting enough magnesium. Most people get it through via their water supply. I’m retired but still enjoy putting in full days of very physical work that depletes my magnesium. I began to take Epson Salt baths and cramping would stop in 10-15 minutes. Now I take these baths regularly 1-3 times a week and cramping is a thing of the past.

      • Supplemental magnesium works amazingly well for restless legs also. Take some before bed, and after one or two nights, RLS will be a thing of the past.

    • After a serving or two of chocolate I get a crampy, “restless” leg thingy at night. I don’t drink coffee because of this and other sensitivities. Thanks for posting!

  77. I feel that I need coffee just to get up to the speed of non-caffeinated humanity. I drink about a cup after each meal, even dinner. It helps my digestion and seems to keep me from eating more. But I’m also careful, paying attention to how different roasts and brands affect me. I don’t like to feel too hyped up and always use cream (preferably) or half and half, and I always consume coffee with a meal that includes adequate protein and fat. A friend of mine, who knew someone in the coffee roasting business, once said that the darker the roast of the beans, the lower the caffeine. I have found this to be true and prefer darker roasts. It’s important to try different brands and then stick with the ones that make you feel good and not crazy. Feeling too nervous just doesn’t seem like a good thing for our bodies.

  78. For me, it seems that even different brands of coffee affect me differently. I could drink Folgers like water and never feel anything from it, but some of the Starbucks varieties are almost too strong and give me stomach problems. Its interesting to tinker and find what works.

    • Yes, Becky, I also get strong stomach reactions from some brands/blends. Consuming coffee with cream or half and half helps. I used to use 2% milk back in the old days of my low fat life, and I experienced far more problems, but still, I must continue to be careful and always have a meal first.

  79. Thank you very much for explaining the 23&me site. I took an introduction MOOC on DNA a while ago which helped me for a time, but I’ve forgotten what I learned and your article helped me get back there.

  80. From dbSNP, about 53% of persons of Euro ancestry are “fast” metabolizers on rs762551, which is used as a marker for both caffeine clearance and for phase 1 liver detox taken as a whole. 38% are “intermediate” and 9% are “slow” on metabolizing caffeine and on phase 1 liver detox generally.

    Compare genetics to actual function of phase 1 vs. phase 2 liver detox in present time with Doctor’s Data lab’s Hepatic Detox Profile, which can be gotten through health professionals or direct-to-consumer at

    Genetically I’m a fast metabolizer on CYP1A2, rs762551, but very fast (99%ile) on phase 1 liver detox per the DD lab report. Fortunately my phase 2 is faster than average both genetically and functionally.

    Genetic and functional testing are complementary and, in my opinion, should be done together for best perspective.

    • HI Carol. Can you tell me how you’ve become so “gene literate”? I have my 23 and me raw data and some “translations” from Livewello and Nutrahacker. Would love to buy a book which could help me to understand.
      I am a slow metaboliser. Because I have been very ill, when I gave up caffeinated coffee, I totally crashed. Have spent 3 weeks in bed. Hard to believe that coffee is that powerful a drug!

      • The population/ethnic percentages in dbSNP for any given SNP, are linked in the 23andme raw data browse.

        I’ve been an avid student of genetics for 6 years now, autodidact, using pubmed, google (where you’re limited only by your imagination), genecards, entrez gene for gene aliases, snpedia, wikigenes, dbSNP and canonical biochemical pathways (I sometimes question these), and lots of observations. I came to biochemistry via genetics, at age 60. I like to cross-reference genetics with functional testing as a reality check. I think it’s dangerous to recommend based on genetics alone without relevant functional testing.

        Your own genetics are good place to start. Then begin to expose yourself to some of the topical SNP lists in LiveWello and comments in Promethease, for example. Survey the supplementary information in 23andme’s raw data browse feature for each gene and SNP.

        Most medical-related genetics reports and education should be considered historically preliminary and are nearly always inadequate, often misleading, with key information omitted, but these reports and education are the beginning of getting exposure to genes and SNPs. Don’t believe everything you hear and read. Rather, step back and reserve judgment until you’ve made enough of your own observations over time. Consumers are used to having everything handed to them on a silver platter, in a nice package all tied up with a bow. Don’t look for that with genetics, it’s a simplistic trap, but will appeal to most people.

        In my opinion, the subject of genetics is for natural systems thinkers, geeks who are also very patient over time, have learned how to be comfortable with ambiguity, devoid of habits like jumping to conclusions and emotionalism, who see information about a system as having intrinsic value with possible applications at some point or maybe never in their lifetime. In other words, surveying a system doesn’t necessarily have to be “actionable” to have value. The average consumer, doctors, and medical insurance companies want “actionable” items, else they see no value and so can’t justify the cost or time. There are more actionable items to be found in functional testing and personal experience. You can learn a lot about genetics from functional testing, finding where these mirror each other and where we find what we might expect to find, vs. where they don’t mirror each other and something else is contributing to a functional or experiential result.

  81. Have not done the gene thing but I’m well aware of drinking coffee after 10 a.m does a number on my sleep as does the consumption of white sugar or high fructose corn syrup products. My brother has the same problem. I can take or leave the coffee but it’s a social activity in the morning and I don’t like tea. As for the sugar once I get started on cookies, cake or sweets of any kind it takes a lot of discipline to knock it off again. I also feel rude when declining deserts when dining at friends. They should look at fast and slow metabolizing of sugars the way they did for coffee. We can do without both.

  82. I am CC, so slow metabolizer. So it comes as no surprise that even a cup with only an inch of coffee in it will get me jacked up. I have given up coffee except for decaf and even that has an effect. If I do indulge, even with decaf I awake with big bags under my eyes. Have not been able to figure out why, but maybe its due to the proteins you mention that some people have trouble with? Its like taking an aging pill, not pretty!

  83. Caffeine has absolutely NO effect on me. I drink tea usually, because I like it and its health benefits, and coffee occasionally, but I also don’t have any negative effects of suddenly going a few days without it. I’d love to know what it feels like to experience the “pep” and sharpness coffee gives people! And I’ve yet to meet anyone else like me. I must be a super-fast metabolizer? I did a little research myself and came to the conclusion that I must be high in an enzyme called CYP1A2 isozyme, which can be raised by eating lots of certain vegetables (which I do) but then why wouldn’t I meet a ton of other people with the same thing? I know loads of vegetarians, for example. What gives?

  84. Hi Wonderful Chris Caffeine inhibits COMT Therefore the suggestion is If you have SLOW COMT Limit coffee intake to one per day or preferably avoid caffeine all together esp if being treated for any Mood Disorder.
    Its all so complex and inextricably linked.We are glad to have people like you and Ben Lynch helping us. Thank you so much.

  85. I have been wondering about this since getting my 23andme results back, great article! I’m A,C. I was a moderate caffeine addict for years–I would brew a 4 cup moka pot of espresso every day, using half for an Americano in the morning, and the rest for an iced latte in the afternoon. However, my coffee consumption dropped to almost zero about a year ago while going through a period of stress. I just didn’t want it, and when I tried drinking coffee later, it made me jittery. Sometimes I even have a paradoxical effect from caffeine–I’ll brew a cup for a pick-me-up, and instead I feel completely fogged and lethargic before I even finish it.

  86. I have never been able to tolerate caffeine. It affects me for the next 3 days (following consumption of even just a 1/2 cup of regular coffee – not even Starbucks super caffeinated coffee). The affects that I have include intense migraine headaches for 2-3 days unless I have more caffeine) and/or jitters for that amount of time as though I am on speed (or imagine that it what it is like anyways!) I have always avoided caffeine. I will check into the DNA – so fascinating. And all these years I have been seen as an outcast!

  87. I must be a fairly slow metabolizer; pretty sure my ex is a fast m. though. He always has to eat the minute he gets out of bed. No idea if that is related to genetics but…if I try to eat, I’d probably throw up – have to be up for at least a couple of hours before eating. Of course, I feel quite addicted to one modest cup in the morning (first thing I do upon waking almost) – fresh-ground dark roasted coffee made in an Aeropress. Having said all this, coffee makes me anxious esp. if I am already experiencing anxiety…..and this differs with the season. In spring, I have had to go to half or all decaff otherwise i can get pretty disregulated. And that’s from only ONE cup of coffee in the morning, with cream. The anxiety can last for hours. Especially if there are a lot of things “undone” like just before Xmas.. My two cents.

  88. I guess I must be a fast metaboliser as I can drink coffee at any time of the day or evening. In fact it has the effect of putting me to sleep in the evening, so if I cannot sleep on occasion I get up and make a small cup of coffee. Having said that I do only drink half strength coffee as never having used a sweetener – cannot keep sweet coffee down – I do not like the bitterness full strength coffee has. People are surprised when I tell them this as almost all say the opposite.

  89. I’ve found coffee useful in some situations. I’m prone to low periods around mid afternoon, and in winter this includes deep coldness and shivering not easily resolved by room temperature or adding clothing. I’ve started using a cup of coffee (organic, very dark roast) most afternoons in cold weather, and this seems to help combat the lethargy and cold. It’s also occasionally helpful for migraines. Interestingly I suffer from anxiety and sleep disturbance, but coffee doesn’t seem to aggravate either (although I don’t drink coffee after about 4 pm to help prevent further sleep disturbance).

  90. For me it seems that coffee itself is the trigger, not caffeine. I.e, it doesn’t matter if I drink caffeinated or decaf, I have the same uncomfortable response. On the other hand, I can drink tea and even natural sodas with caffeine.

  91. I went without coffee for a few months, but I got so depressed I couldn’t function. Coffee is the only effective anti-depressant I know of, and I’ve tried all the pharmaceuticals. I’m sure I’m a slow metabolizer because I can’t drink it past noon and expect to sleep that night. Other than that, no obvious side effects, and it restores my energy and desire to get things done. My one cup in the morning, regardless of risks, is totally worth it to me.

  92. Great article. I am A/A (fast metabolizer), which I have always known this because for the most part I can tell no difference from drinking a single cup of coffee to drinking an entire pot of coffee. I’ve always thought that was odd.

    Additionally, I can stop drinking coffee cold turkey (I drink several cups a day) and I never get headaches or have any other discernible symptoms of withdrawal either.

    We have a lot to learn.

  93. I have never felt the focus or wakefulness coffee is supposed to give. But ive felt the anxiety.
    Is this possible? To react to one and not the other?

  94. Chris,

    I am very interested in having genetic testing done. However, I noticed that 23andme had terrible reviews on Amazon in part because of their privacy policies. Smart DNA does not have any reviews, other than on their Facebook page. Have you been fairly satisfied with both companies?

    Thank you for your posts. They are always interesting.

  95. Diagnosed with hypoglycemia in the 1970s and advised to avoid caffeine. I was not able to give it up entirely for the next 30 years. Can’t help wondering if hypoglycemics, generally, are slow metabolizers of caffeine.

  96. I probably drink too much coffee: usually 5 cups a day. I am 73, and I have never experienced any bad reactions to coffee. I sleep as a child at night, whether or not I have had a cup just before bedtime (I like to finish my day sipping coffee).

    But if for some reason I do not have any coffee at all during the day, I get headaches towards the evening and find it less easy to concentrate. This makes me think that maybe I am a coffein addict, and that I should benefit from stopping the habitual coffeedrinking after all.

  97. I had one cup of cafe au lait (1/2 milk, 1/2 coffee) when I was 10. I remember that it was delicious. I could not sleep for one moment the entire night. At times that night I couldn’t even lie down. I have NEVER drunk coffee since! Black tea keeps me up 1/2 the night so none for me. Chocolate does the same but sometimes I indulge anyway; always sorry when I do. Green tea makes me sleep 4 hours a night but feel good in spite of it, lol. As much as I adore green tea, I avoid it.

  98. Back around 2009, at the age of 55, I was actually prescribed coffee by a chronic fatigue doctor. I had never been a coffee drinker until that point. He wanted to give me Provigil but I refused. At that point in time, I had pretty much no caffeine intake. I started putting coffee in smoothies and gradually developed a taste for it and drink 3 to 4 cups daily. I never get energized by it but I do feel more awake and can think more clearly. I could drink coffee at 10PM and go to sleep by midnight. When I did 23andme, found out I’m a fast metabolizer.

  99. I am a slow metabolizer (CC) and I seem to be ok with 1 espresso but if I drink drip coffee I am set for a disaster. Bloating, pain, jitters and disturbed sleep. Same thing happens if I drink a lot of “Yerba Mate”. Seem to be ok with green tea though.

    Thanks for the article!

  100. I have a feeling I’m a slow metabolized of caffeine. If I have it even in the am it makes it hard to sleep. I also find for me drinking caffeinated tea is even worse.

  101. There is research that shows coffee increases LDL cholesterol levels. This may or may not be a bad thing depending on your views of the lipid hypothesis. My personal experience however has been that over two periods when I consumed coffee my LDL spiked and when I went back on Green tea (research suggests this lowers LDL), it came back down. I am an AA gene for coffee by the way.

    • I have extremely high cholesterol and I have quit drinking unfiltered coffee as in espresso. A filter helps with cholesterol issues.

    • I’ve heard about the ldl-raising effects being due to oils in the coffee that are present in French press coffee but not when poured through a paper filter.

  102. I think it has to do with Coffee or caffeine as a diuretic. I have the same issues with coffee as many post here. By being a diuretic, your purging your body of minerals, and if you drink coffee all the time, daily in the AM or anytime for that matter, your depleting minerals all the time. An example of this is when doctors prescribe for the elderly diuretic drugs to reduce swelling in legs. This is typically because of heart or diabetic issues. But when they get diuretics it massively depletes minerals, especially Potassium and sodium, so likely many more minerals are depleted like Magnesium. Then these elderly have issues with balance and falling. I have had three family members with these issues the last few years, and all were mineral deficient. Recently it was my MIL. Fell twice.

    So IMO the reason for possible sensitivity to caffeine even me, Is loss of minerals. Just my observation.

    • Chris, I need to know this…. I’d heard that coffee pulls out minerals, years back. Is that proven by research or is it just a belief? If you drink it with heavy cream as I do, and a little mineral rich palm sugar, would that change this? Should one up their magnesium and/or multi-mineral when drinking coffee?

    • I’ve read the diuretic effect of coffee is temporary – only an issue when one begins drinking it initially, but then the body becomes accustomed to it and adjusts to the effect in such a way that it no longer acts like a diuretic.

  103. I’ve always been very sensitive to caffeine and am unable to tolerate coffee (sadly, as I love the flavor and ritual). Similarly, I find black tea to be too much caffeine (in French this is called “theine”) for me; it makes me jittery and then my blood sugar will crash.

    I do drink green tea though I usually balance this with food. Are there other markers for people who are sensitive to other types of caffeines, like those found in tea? I really enjoy green tea and the light buzz I get from it—but sometimes I wonder if it taxes or invigorates my system. On the other hand, I find that the caffeine in dark chocolate is a non-issue to me unless I eat it late at night; the larger factor seems to be the sugar content. I would love to continue to drink green tea but would love to know if I’m better off without caffeine at all? Or more likely it’s a question of timing and moderation… Any thoughts appreciated!

  104. AA here. I drink 4 cups of coffee a day. I try not to drink any after 4pm generally – I prefer bone broth after that.

    However I have been able to drink a double espresso as late as 11pm and still get to sleep no problem by a little after midnight. I can clearly drink as much coffee as I want, anytime, without issues at all.

    But I was just raised that there are certain good manners around food & drink. Like you don’t drink alcohol before noon, you know? 😉 And you don’t drink wine without eating. And you don’t have candy for breakfast. 😉 I suspect most of us were raised the same way.

    So unless I’m in Italy, I won’t drink coffee in the evening. But in Italy I will take a tiny shot of espresso after dinner if the rest of the group does. 😀

  105. I never used to be a coffee drinker until I had kids, and then started drinking 1 cappuccino per day, in the morning. Then my sleep went down the drain, even after my 9 month old started sleeping through the night. It was only after completely giving up coffee and alcohol that my ability to sleep came back. Now I feel jittery even with a cup of decaf. And can’t sleep if I have even half a cup of wine.

  106. This article is right on time for me. In recent months, I have found myself extra sensitive to coffee. I have always known an afternoon cup would affect my sleep that night. Yesterday, I started a coffee taper. Every other day, I step down a little until I am coffee-free by 12/31. I plan to stay off for all of JAN then reintroduce later to see how I do. I may not even reintroduce it if I feel good. Reading your article has me convinced I made the right decision. Thank you!

  107. I used to be more sensitive to coffee, in a bad way.. a cup might punish me later in the day with greater chance of nausea, unstable blood sugar… and during perimenopause, one cup in the morning might wreck my sleep that night. Oddly, in the past few years I have become a regular, happy morning coffee drinker (only organic and freshly ground) and find that it positively affects my brain function, both as an anti-depressant and an anti-fog measure, and doesn’t disrupt my sleep if I have it before 2pm. (And I do badly with black tea!) Coffee even seems to help my digestion, if I drink a dark roast. Lighter roasts can provoke reflux, and it took me a while to figure that out and find a couple of favorite varieties that don’t. How’s that for a lot of specifics? 🙂 Also, I rarely see this mentioned– but I understand that coffee is heavily pesticided, so that one should always choose organic.. do you agree? Shouldn’t this variable be factored into all the research? Otherwise we could make the same mistake as the meat researchers, counting organic pastured beef as the same product as factory farmed. (Same with organic wine, etc…)

    • Oh also I discovered that French press coffee triggers reflux for me, probably because you get some of the sludge of the beans. I drip mine through a brown paper filter and am good to go. I share these things with the hope that it will help others.

      • I agree, Carey. I think it is very important to clarify whether the coffee used in these tests is organic, free trade or commercially produced. In addition the source (country of origin) should be indicated too. All of these I think will make a significant difference in the results.

  108. I have been on and off coffee for the past few years, figuring out if it works for me. At this point I have determined that regular drip coffee does not agree with me at all. It makes me bloated and full, sometimes nauseous, on top of being jittery. Espresso seems to be fine though, and if I have coffee I will have an Americano (espresso with hot water). Any thoughts on why this could be?

  109. My naturopath recently told me that coffee (not caffeine) has a negative effect on women’s hormones. Is this something that has come up in your research?

  110. I’m ‘AA’ on rs762551 but even a single cup at 8AM gives me jitters, muscle twitches and disturbs my sleep. The effect seems to accumulate over 2-3 days at which point I just can’t drink anymore.
    I’m 36 now and developed this ‘intolerance’ over the past 3 years. I used to drink 2 double espressos per day before this.
    Blood work is normal, including liver enzymes.
    Any ideas what can it be?

    • I think this highlights something I mentioned in the article, which is that there’s still a lot of individual variation even within a given genotype. There are likely many other genes that play some role in caffeine metabolism that we’re not looking at, and of course general liver function and detoxification capacity, sleep, HPA axis function, etc. will have an impact.

      • On my 23andme variant report that I ran through MTHFR Support I am AA which is ‘normal’. But you list that as a fast metabolizer. Shouldn’t AA be the average (neither slow nor fast) metabolizer since it is the common variant?

      • I have had similar experience, not with coffee, but with dark chocolate.
        In my 30’s, I started to become very sensitive and seemingly intolerant of it and I suppose due to the stimulants. I will get heart arrhythmias, impaired sleep, irritability (after some hours, if too much) etc. It is also cumulative: after a few days of having it, it seems to build up. An ounce or two spaced out doesn’t seem to have side effects. I also notice correlation with menstrual cycle (worst in last week), which it exacerbates, unfortunately when it is most craved!

        A few years before this, I suddenly developed intermittent insomnia, which I am guessing is related to HPA axis dysfunction; anxiety suddenly increased as well. The main symptoms are almost like caffeine, which I am assuming are adrenaline/stress hormones; I have had several salivary cortisol tests timed throughout the day, however, which all looked with in ‘normal’ limits. However, the symptoms feel like I had a shot of espresso and always occur early morning, about 4:30-6:00am: strong, increase pulse, feeling hot, wired/wide awake, and restless.

        Any insight or shared fellow experience is greatly appreciated!


      • I’ve heard that other genes may play a role but ruled that out since I used to be a casual coffee drinker before.
        I suspect liver because the same intolerance to alcohol seems to cripple.
        How can I measure my liver detoxification capacity if liver enzymes are in range? Had slightly elevated fibrinogen but doc said it wasn’t the liver as enzymes were ok.

      • Article of Molecular Psychiatry (2012) 17, 1116–1129; doi:10.1038/mp.2011.101. Genome-wide association analysis of coffee drinking suggests association withCYP1A1/CYP1A2 and NRCAM has listed many more possible variants affecting caffeine metabolism. Even this one was naturally done in cell lines.

        There still (to my knowledge) are no studies were genotyped people were given standardized dose of caffeine and measured for caffeine metabolism for a day as these kind of studies are expensive and no profit to anyone.

  111. Every time I drink coffee I get anxious, almost depressed, and feel like I’m coming down with a cold. My Mom is the exact same way and it’s been like this my whole life.

  112. because i know i am hetero for comt i think i am a fast and slow metabolizer. taking methylcobalimin really helps but i have greatly reduced my consumption to one half cup bullet proof in the am and i am fine. but generally i stay away from it. could check my CYP1A2 but i am fine with this protocol. not ready to try the month off yet…..

    love your work, chris.

    many thanks, nancy, monterey, ca

    • I am a fast metabolizer of caffeine according to 23andme. If I drink too much coffee (more than 2 cups in morning and 1 early afternoon only) I don’t sleep well. I usually do 2 cups of strong coffee before 9:00 am and green tea in afternoon and do just fine. I can also take a nap around 11:00 if I want to. And I LOVE coffee: the smell, the ritual in the morning, the bitterness of it. I have titrated off caffeine many times just to “reset” and I can totally tell the difference in flavor in decaf – it tastes flat to me. (And I buy the good, locally roasted dark beans).

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