Why Does Poop Smell? Doctors Weigh In

It's probably something you ate—but it could be one of these other potential causes of stinky poop.

We all poop. And quite frankly, it never smells good. (Thank heavens for air freshener!) But sometimes your trip to the bathroom can produce a particularly rancid dump. It may freak you out—and have you asking yourself, “What the hell is going on?!”

Chances are it’s probably something you ate—and nothing to worry too much about, says Daniel Freedberg, MD, a gastroenterologist at NewYork-Presbyterian Hospital and Columbia University Medical Center. "The way diet affects odor of stool is by changing the stool bacteria. Depending on which stool bacteria are present, they make different gases, and those are the (not-so-pleasant) gases we smell."

Still, there could be other reasons poop smells. Health talked to gastroenterologists to find out all the possible culprits for extra-smelly poop.

You drank a lot of booze

The bathroom the morning after a night out can smell toxic. "High blood alcohol levels can affect other organs—like the stomach and the small and large intestines—altering motility, the permeability of the intestinal wall, and the pre- and probiotics of the intestinal flora," says Christine Lee, MD, a gastroenterologist at Cleveland Clinic.

This can cause loose stools, diarrhea, and a change in the smell of your poop.

"Furthermore, alcohol has significant amounts of sulfate," says Dr. Lee. "The more sulfate consumed, the more it is available for colon bacteria to make sulfide gases, and sulfide gases can have an offensive stench."

You're taking certain meds

Some prescriptions can also mess with the smell of your poop.

Medications like antibiotics or hormones can mess with gut bacteria, speed up or slow down the way poop moves through your intestines, or cause "malabsorption of certain nutrients, thereby causing smelly diarrhea," says Dr. Lee.

You're lactose intolerant

If you're lactose intolerant and eat dairy, you know it will eventually send you running for the bathroom—and it could be extra stinky.

"If you are lactose intolerant, lactose gets passed along the intestine, causing a nasty, smelly, malabsorptive diarrhea," says Dr. Lee.

You're taking certain supplements

They could be benefiting your body, but they might make the bathroom smell terrible.

"Certain supplements like glucosamine, chondroitin, and garlic are high in sulfate, which the bacteria in the colon converts into sulfide gases," says Dr. Lee.

You're eating a lot of foods with sulfur

These include cruciferous veggies, dairy, eggs, and meat.

But just like booze or supplements with sulfates can make poop smell, so can sulfur-rich foods. "Sulfur is a necessary element in our diet, and certain foods high in sulfates increases sulfur gas," says Dr. Lee.

You have a high-fat diet

A high-fat diet may overwhelm your digestive system, and your gut may not be able to break down all the fat consumed.

"The 'unbroken down' fat cannot be absorbed, and thus it’s passed to the colon in its undigested state. This results in a smelly diarrhea with a very high fat content, called steatorrhea," says Dr. Lee.

You have a gut disease or infection

If you don't eat a high-fat diet but you still find yourself with steatorrhea, it’s possible something more serious could be going on.

"Unabsorbed fat in your stool could signal Celiac disease or pancreatic diseases," says Dr. Freedberg.

"Steatorrhea can produce uniquely malodorous diarrhea that’s often described as loose and oily," says Dr. Lee.

Intestinal infections may also be to blame. "Infections in your colon, like Clostridium difficile, can cause a very distinctive foul-smelling diarrhea," she says.

You eat a lot of sugar alcohols

You might be opting for sugar-free foods to save on calories, but they can also make your poop smell a lot worse.

"Sorbitol in particular works like a laxative by drawing water into the large intestine and inducing diarrhea, and it generally has a stinking smell," says Dr. Lee.

When to see a doctor about smelly poop

"Vile-smelling poop may indicate a serious problem," says Dr. Lee. Certain red flags warrant a call or a visit to your doctor.

The first is if you see blood in your poop. "Blood in the GI tract tends to be distinctively foul-smelling and may appear black in color,” Dr. Lee says. “The texture may also be ‘sticky’ like fresh asphalt on a hot summer road."

If you do notice fatty or oily stools, talk to your doctor about the chances you may have a more serious gut disorder or infection.

It’s also worth a trip to the doctor if your poop size, color, or frequency changes significantly or if you feel pain while pooping.

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