Everyone poops, and it’s never exactly fragrant. But sometimes, your bowel movements might have an unusually strong, foul odor. This can be alarming, leaving you wondering if something is wrong.
Often, the culprit is simply something you ate – nothing to worry about, according to Daniel Freedberg, MD, a gastroenterologist at New York-Presbyterian Hospital and Columbia University Medical Center. “Diet affects stool odor by changing gut bacteria. Different bacteria produce different gases, and those are the (unpleasant) smells we notice.”
However, there are other potential reasons for foul-smelling stools. Let’s explore some common causes.
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Alcohol Consumption
Heavy drinking can lead to particularly smelly bowel movements the next day. “High blood alcohol levels can impact organs like the stomach and intestines, affecting motility, intestinal wall permeability, and the balance of gut bacteria,” explains Christine Lee, MD, a gastroenterologist at Cleveland Clinic.
This disruption can cause loose stools, diarrhea, and changes in stool odor. “Alcohol also contains significant amounts of sulfate,” adds Dr. Lee. “More sulfate means more sulfide gas production by colon bacteria, leading to a strong stench.”
Medication Side Effects
Certain medications can also alter stool odor. Antibiotics and hormones can disrupt gut bacteria, change the speed of digestion, or cause malabsorption of nutrients, leading to smelly diarrhea, according to Dr. Lee.
Lactose Intolerance
If you’re lactose intolerant, consuming dairy products can result in foul-smelling stools. “Lactose passes undigested through the intestines, causing malabsorptive diarrhea with a nasty smell,” says Dr. Lee.
Supplements High in Sulfate
While beneficial for overall health, some supplements can contribute to unpleasant stool odor. “Supplements like glucosamine, chondroitin, and garlic are high in sulfate, which gut bacteria convert into smelly sulfide gases,” explains Dr. Lee.
Sulfur-Rich Foods
Foods like broccoli, cauliflower, kale, dairy, eggs, and meat contain sulfur. Similar to alcohol and supplements with sulfates, these foods can increase sulfur gas production, making both stool and gas smellier, says Dr. Lee.
High-Fat Diet
A diet high in fat can overwhelm the digestive system. “Undigested fat passes to the colon, resulting in smelly, fatty diarrhea called steatorrhea,” explains Dr. Lee.
Underlying Medical Conditions
Steatorrhea, characterized by loose, bulky, pale, and foul-smelling stools, can indicate more serious issues if not caused by a high-fat diet. “Unabsorbed fat in stool could signal Celiac disease or pancreatic problems,” warns Dr. Freedberg. Intestinal infections, such as Clostridium difficile, can also cause distinctively foul-smelling diarrhea.
Sugar Alcohol Consumption
Sugar-free foods often contain sugar alcohols like sorbitol, which can worsen stool odor. “Sorbitol acts as a laxative, drawing water into the intestines and inducing diarrhea with a generally stinking smell,” says Dr. Lee.
When to Seek Medical Attention
“Extremely foul-smelling poop may indicate a serious problem,” cautions Dr. Lee. Red flags include blood in the stool (often black and sticky with a foul odor), fatty or oily stools, significant changes in stool consistency, color, or frequency, and pain during bowel movements. Consult your healthcare provider if you experience any of these symptoms.
