Coffee Makes You Poop
A small study in 1990 found that 29% of people reported that they poop after drinking coffee, and people who reported this also had increased movement in the distal colon (the last part of the colon) for at least 30 minutes after they drank coffee. So for some people, coffee makes things ~move along~ more quickly.
"Basically coffee stimulates the contractions of the stomach and intestinal tract, and it stimulates bile excretion, which itself is a propellent of food particles because the intestines know that when there is bile there is food," says Alden. "Coffee also helps to release gastrin, a hormone that plays a role in the motility of the intestinal tract."
TL;DR: All this movement means that your colon is hard at work to push out whatever's in there.
It could just be that your gastrointestinal tract is waking up after being inactive all night. That's called the gastrocolic reflex, which happens when food or drink enters an empty stomach.
"When you have coffee first thing in the morning, it triggers the gastrocolic reflex, which is a hormonal message sent to the colon that it's time to contract to make room," says Chutkan. This reflex could be more pronounced in people with bowel disorders like IBS.
Regular, decaf, espresso, pumpkin spice lattes — they can all have this effect on some people, but not others. According to the study we mentioned earlier, this effect was reported with regular and decaf coffee. Plus, it's not something people typically notice with caffeine-containing drinks or supplements, says Alden.
But if you take your coffee with cream or milk and you’re sensitive to dairy, that could also explain some mid-morning crapping.
Try drinking it black or with non-dairy creamer to see if that helps.