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

Coffee Is Good for You—Unless It’s Not!

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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.

slow caffeine metabolism
Many feel that coffee is an important part to the start of their day. istock.com/kyoshino

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.

177 Comments

Join the conversation

  1. 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?

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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!

  8. 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.
    Marcia-Roscoe,IL

  9. 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.

  10. 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.

  11. 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!

  12. 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. 😀

  13. 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.

  14. 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!

  15. 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.

  16. 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?

  17. 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?

  18. 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!

        J.

      • 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.

  19. 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.

  20. 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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