Can Coffee Make You Poop?

Coffee is known as a stimulant that helps people stay alert and awake, mainly because of the caffeine that it possesses. But for many people, it can act as a type of laxative and can cause them to have a bowel movement quickly after consuming the coffee. It can induce motor activity in the colon and causes many people to have the urge to defecate within minutes to an hour after drinking it. In layman's terms and to put it bluntly, coffee can make some people poop. For a small number of people it can even cause diarrhea, though this effect isn't nearly as common as the effect of having a regular bowel movement is. Some people who are affected by coffee may wonder if it's normal or if it's a sign of a serious underlying illness or problem. It can be, but for the vast majority of people it's completely normal to feel like you have to go to the bathroom after drinking coffee or consuming any products made from coffee seeds (also known as coffee beans).

Many people who don't feel any effects on their bowel movements from it sometimes say it's a myth or "all in your head" to those who do feel it. The people who say or think that are simply wrong. Just because something doesn't affect them, that doesn't mean that it's a delusion of those who are affected. There are many credible studies on coffee's effect on the bowels and the colon of the human body. Majority of the studies have concluded that there is a large percentage of people in the general population that have to defecate (poop) after drinking it. So below I've covered just a few of the most prominent studies on it to serve as proof that coffee does send some of us straight to the toilet after all.

In the first study, scientists wanted to see if warm water, nicotine, or caffeinated coffee had any effects on a person's bowel movements. If any of these did have an effect, they also wanted to establish which ones had the greatest or least effect. They recruited 16 people and split them up into two groups and studied them on two different days. On the first day they gave half of them coffee and the other half warm water. On the second day they gave half of them nicotine and the other half a placebo. They measured the effects of these things on the body by measuring each person's rectal tone after consumption. What they found was that both warm water and coffee caused people to have bowel movements, but they didn't notice much of a difference between the two, with coffee only having a very slight difference in rectal tone compared to the warm water. Nictone, on the other hand, showed no effect on bowel movements in any of the people who participated.

Scandinavian Journal of Gastroenterology. 2005 Jul;40(7):808-13.
Stimulation of defecation: effects of coffee use and nicotine on rectal tone and visceral sensitivity.
Department of Gastroenterology and Hepatology, Erasmus Medical Centre, Rotterdam.

In the second study, researchers asked ninety nine people who were in their late teens to late 20's what types of drinks caused them to have bowel movements. About 29% of them said that coffee was the main culprit for them which caused them to defecate (poop) after drinking it. The researchers then recruited fourteen people, eight of which were some of those who said on the questionaire that coffee affected them. They evaluated all fourteen of these people by testing their rectal and colon responses using multiport manometry and by having them drink caffeinated black coffee (without any sugar or sweetener) on one occasion and decaffeinated black coffee on another. They found that with both types of coffee, all eight people who said that it affected them showed responses on the rectum and colon tests in less than four minutes. These responses continued for at least a minimum of 30 minutes after the people drank both types of coffee. The researchers then tested the same fourteen people on a different occasion and in a similar way but with warm water instead of coffee. They found no significant response in any of the fourteen people when it came to water.

Gut 1990 Apr;31(4):450-3.
Effect of coffee on distal colon function.
Subdepartment of Human Gastrointestinal Physiology and Nutrition, Royal Hallamshire Hospital, Sheffield.

In the third study, the researchers aimed to not only establish if caffeinated coffee causes more of a colon response than decaffinated coffee and regular water, but also whether it has more of a response on people than eating a 1,000 calorie meal. They used manometry devices in the colon on 12 people and tested them with the three different types of drinks and the 1,000 calorie meal. They did this over a 10 hour period to give the people some time in between each drink and the meal, and all the drinks were at the same temperature of 45 degrees. The results showed that caffeinated coffee, decaf coffee, and the 1,000 calorie meal all caused increased movement in the colon as well as more contractions, and all three of the drinks had different levels of effects. Caffeinated coffee and the 1,000 calorie meal had similar effects on the colon, but they were both 60% greater in impact than the water and 23% greater than the decaf coffee. What they also found was that most of the effects of both types of coffee and the meal occured in the upper colon (transverse and descending colon) compared to the lower colon or rectal area (rectosigmoid colon), which may explain why the first study found little differences between coffee and warm water when checking rectal tone.

European Journal of Gastroenterology & Hepatology. 1998 Feb;10(2):113-8.
Is coffee a colonic stimulant?
Rao SS, Welcher K, Zimmerman B, Stumbo P.

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