The Real Reasons Behind Why Alcohol Can Cause Strange Bowel Movements, According to Experts

If your adult beverages are leaving your digestive system in distress, there’s one simple explanation: Alcohol is an irritant to the GI system, and it can inflame the lining of the digestive tract, from the esophagus to the large intestine, explained Dr. James H. Tabibian, a board-certified gastroenterologist at Adventist Health in Glendale, California. “This, in turn, disrupts the normal functions of the GI system, which regulate bowel movement production,” he added.

Specifically, alcohol increases gut motility, or how fast contents move through your gastrointestinal system, Sohi explained. Since your body is trying to remove the alcohol quickly, the colon — which is responsible for pulling water out of the digestive tract and reabsorbing it in the body to prevent dehydration — doesn’t have enough time to do its job, added Dr. Lauren Bleich, a board-certified gastroenterologist with Gastro Health in Acton, Massachusetts. 

With more liquid in the large intestine and increased motility, you may end up with softer, more urgent stools, according to the experts. “If the body’s trying to go super fast and eliminate this toxin, it’ll just dump, and so you’ll see loose stools,” Bleich added.

How quickly you feel the urge to use the restroom while drinking — or if your bowel movements change at all — varies from person to person, according to the experts. “No one’s body reads like a textbook,” Bleich said. “It can be an hour or so later … but it can sometimes be the next day.” Still, folks with chronic gastrointestinal conditions such as irritable bowel syndrome, inflammatory bowel disease or celiac disease may experience symptoms in a more heightened and urgent way, Sohi added. 

While soft stool and diarrhea are the most commonly experienced GI side effects, some individuals may suffer from constipation after a night of drinking, according to the experts. Alcohol suppresses the secretion of vasopressin, a hormone that regulates the body’s ability to retain water, Sohi said. Specifically, the hormone decreases water excretion by the kidneys and increases water reabsorption, leading to antidiuretic effects. “That [suppression] is why people will pee more when they drink,” Sohi explained. For the folks who feel backed up after a wine night, “the alcohol is making them pee out all the water in their body, and so they get dehydrated and then constipated because of it.”

With chronic alcohol use comes additional, often more severe, GI effects. “Alcohol can alter the balance of intestinal bacteria and lead potentially to bacterial proliferation, or overgrowth, which can cause diarrhea, as well as other symptoms like bloating,” Tabibian said. This bacterial imbalance (known as intestinal dysbiosis) is generally the result of chronic, frequent alcohol use, though occasional drinking can cause some temporary changes, too, he explained.

Drinking frequently can also cause permanent damage to the digestive tract, which can lead to frequent bouts of diarrhea, Sohi said. Chronic pancreatitis is possible; the condition inhibits your ability to absorb nutrients (particularly fat) and can cause chronic diarrhea, she noted. Of course, excessive alcohol use can lead to a host of other health problems, too, including cancer, high blood pressure, heart disease, stroke and liver disease, among others. 

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