Coffee is good for you—unless it’s not! | Chris Kresser
Interested in becoming an ADAPT Certified Functional Health Coach? Enrollment is open now and closes September 30th Learn More

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


Last updated on

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.

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?”


Join the conversation

  1. 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!

  2. 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.

  3. 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.

  4. 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.”

  5. 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

  6. 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.

  7. 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!

  8. 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.

  9. 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!

  10. 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.

  11. 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. 😉

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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!

  17. 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?

  18. 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.

  19. 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.

  20. 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.

[if lte IE 8]
[if lte IE 8]