A recent study looked at the effects of coffee on the microbiome of the gut. First, the researchers determined the bacterial composition of bacteria in coffee drinkers and non-coffee drinkers, and found they were different.

    Next, the coffee drinkers stopped it for two weeks, and their microbiome changed. Finally, the coffee drinkers started drinking it again, but half were given decaffeinated coffee, half regular. The scientists found that coffee has an effect on the microbiome independent of caffeine. Coffee contains a wide variety of polyphenols that are now known to be a part of the gut microbiome’s diet.

    This study interested me for a few reasons. Like many in the medical field, I made it through the sleep-deprived years of my training by drinking coffee. Back then, I wondered what the point of decaffeinated coffee was. But it turns out that other things in coffee besides caffeine contribute to its effect on mood and cognition.

    The main way I use coffee, both personally and in my practice, is as a coffee enema. I am frequently asked whether coffee enemas affect the gut microbiome. Not surprisingly, no one has ever studied this. From a theoretical point of view, drinking coffee provides all the components of coffee to the gut bacteria for a long period of time. Coffee enemas are retained only briefly, so the gut bacteria would not have long to work on it.

    I am also frequently asked how far into the intestinal tract the liquid in an enema actually goes. I did find a few studies discussing this. The participants in one study had ulcerative colitis, making their gut abnormal. The enema liquid traveled at most to the sigmoid colon.

    In another study, prior to the enema, patients had done an intestinal cleansing preparation such as is commonly done for colonoscopy. This means that the liquid could travel upwards more easily. Even so, for most patients, the liquid did not travel the length of the colon without special efforts.

    My conclusion is that coffee enemas do not travel high enough in the colon to affect the reservoir of bacteria present in the cecum, the section of colon farthest from the anus.

    What difference does all this make? Right now, none at all. But should the medical world ever get interested in studying coffee enemas, articles like this could provide a springboard for testing ideas.