By Leah S. Dunaief

All of you devoted coffee drinkers, and that includes me, might like to know the information in an article in The New York Times headlined, “Why does coffee make me poop?” Written by Alice Callahan and published on Dec. 7, the story explains cause-and-effect, providing some understanding of what is happening in our bodies when we drink java. (That’s where it originally came from, hence the name.)

Not much is known about the precise mechanism of how coffee affects the gastrointestinal tract, but we do know that it can be a laxative.

“Coffee is a complex beverage containing more than 1000 chemical compounds, many of which have antioxidant and anti-inflammatory properties,” according to The Times. This is also why drinking coffee is generally encouraged since it is considered to be a healthy beverage in moderation.

A gut reaction to the intake of coffee can surprisingly happen in a matter of minutes. How does drinking coffee on one end stimulate the other end of the GI tract so quickly? The answer is that a signal probably goes through the gut-brain axis, meaning that the arrival of coffee in the stomach, which happens in 4 minutes, stimulates the brain to send a signal to the colon to empty itself. The coffee actually takes an hour to travel through the small intestine and reach the far end of the colon.

“This communication between the stomach, brain and colon [is] called the gastrocolic reflex [and] is a normal response to eating,” according to The Times. 

But coffee has an outsized effect, stimulating colonic contractions as if a full meal had been consumed. The messaging is thought to be caused by one or more of the chemicals in coffee, and may be aided by some of our own hormones. Examples of such hormones are gastrin and cholecystokinin, which can spike after coffee drinking. 

It is not the caffeine that is the stimulant, however, because those who drink decaffeinated coffee can experience the same stimulatory effect on the colon. This makes coffee a useful tool in dealing with chronic constipation, along with eating more fruits and vegetables, which are high in fiber, drinking more fluids and getting more exercise. Incidentally, a brewed cup of coffee contains a small amount of fiber, one gram for an 8-ounce cup. Fiber is necessary for good gastrointestinal activity.

I have always been a coffee drinker, although my parents wouldn’t let me have some, saying it wasn’t good for children. But I found the smell of it irresistible and began drinking it in college, especially to facilitate those late-night assignments. But right around the time my second child was born, I started getting migraines that were triggered by the caffeine in coffee. This would suggest that a heightened state of hormones plus coffee with caffeine were upsetting my colon and causing trouble along my gut-brain axis. I have satisfied my coffee desires with decaf, but I will tell you what many of you decaf drinkers know: the taste and the effect are not the same. I do miss that lovely surge of energy to start off the morning.

It’s surprising how little we know about how coffee affects us. The most valuable study of digestion, in general, was done between 1822 and 1833 by William Beaumont, an American Army surgeon, on the French Canadian, Alexis St. Martin, a boatman employed by a fur company. St. Martin was shot in the abdomen on Mackinac Island in a near-fatal accident, and the wound did not heal properly, leaving a hole in his stomach. This provided a window of sorts for Beaumont to watch the digestive process. He learned much about the stomach, gastric juices and how digestion works, and he published those observations. But he doesn’t seem to have advanced our understanding about coffee’s effects. Perhaps neither man drank coffee.

To this day, I still say that the best part of coffee, regular or decaffeinated, is its smell.