Why Does My Poop Smell So Bad? 9 Possible Reasons

We spoke to gastroenterologists to understand when smelly poop is from something you ate or drink and when it might be a reason to see your healthcare provider.

We all poop and it never smells good. But sometimes, your trip to the bathroom can seem smellier than usual. It may freak you out, and you may wonder if you should be concerned.

Chances are it's probably something you ate—and nothing to worry too much about, Daniel Freedberg, MD, a gastroenterologist at New York-Presbyterian Hospital and Columbia University Medical Center, said. "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 why your stool smells so bad. So Health talked to gastroenterologists about the possible culprits for stool that smells worse than usual.

Man sitting in public restroom

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You Drank a Lot of Alcohol

The bathroom the morning after a night out can smell especially bad. "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," Christine Lee, MD, a gastroenterologist at Cleveland Clinic, said.

This effect on other organs can cause loose stools, diarrhea, and a change in the smell of your stool.

"Furthermore, alcohol has significant amounts of sulfate," Dr. Lee said. "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 Medications

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

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

You're Lactose Intolerant

Lactose intolerance is a condition where your body cannot break down the sugar lactose, commonly found in dairy. It can cause several symptoms in your digestive system, including diarrhea and gas. If you're lactose intolerant and eat dairy, 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," Dr. Lee said.

You're Taking Certain Supplements

Your supplements could be benefiting your body, but they might also 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," Dr. Lee said. Sulfide gases stink, and when it's released from your stool, they can be a reason your stool smells so bad.

You're Eating a Lot of Foods With Sulfur

Sulfur-containing foods include cruciferous veggies (examples are broccoli, cauliflower, and kale), dairy, eggs, and meat.

But similar to how drinking alcohol or taking supplements with sulfates can make your stool smell, so can sulfur-rich foods. "Sulfur is a necessary element in our diet, and certain foods high in sulfates increase sulfur gas," Dr. Lee said. So while sulfur-containing foods are part of a healthy diet, they can make both your stool and gas smelly.

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 smelly diarrhea with a very high-fat content, called steatorrhea," Dr. Lee said.

You Have a Gut Disease or Infection

According to StatPearls, updated in May 2022, steatorrhea produces stools that are loose and large in volume. They may also be paler in color and produce a smell that seems smellier than normal. If you don't eat a high-fat diet but still find yourself with steatorrhea, something more serious could be happening.

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

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

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

If you find yourself experiencing diarrhea you are concerned about; it is a good idea to check in with your healthcare provider.

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 stool smell a lot worse. This is because many sugar-free foods contain a type of sugar alcohol called sorbitol. Sorbitol is also commonly found in chewing gum.

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

When To See a Healthcare Provider

"Vile-smelling poop may indicate a serious problem," Dr. Lee said. In addition, certain red flags warrant a call or a visit to your healthcare provider.

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

Also, if you do notice fatty or oily stools, you may want to talk to your healthcare provider about gut disorders like celiac disease or a possible gastrointestinal infection.

It's also worth a call or trip to your healthcare provider if your stool size, color, or frequency changes significantly or if you feel pain while pooping.

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