Why might your poop float?
There’s a wide range here. Poop that floats could be nothing—or it could be something for your doctor to look into.
Gas: “The most common reason for floating stools is your diet and, typically, gas within your diet,” says Rudolph Bedford, MD, a gastroenterologist at Providence Saint John’s Health Center in Santa Monica, California. “People on a high-fiber diet may have floating stools.” For most people, if you cut back on the fruit and veggies for a few days, your poop may start sinking to the bottom again.
Malabsorption: Floating poop can also be a sign that your body isn’t absorbing nutrients as well as it should, especially if your BMs are particularly stinky or have an oily sheen, says Ellen M. Stein, MD, associate professor of medicine in the division of gastroenterology and hepatology at Rutgers Robert Wood Johnson Medical School. “One cause of oily, floating stools is malabsorption from lack of pancreatic enzymes,” she says. “Patients with a history of pancreatitis, cystic fibrosis, or pancreatic enzyme insufficiency can have not enough pancreatic enzymes in their guts.”
Those enzymes help digest proteins and fats and, without those enzymes, the nutrients are quickly shuttled through the gut and aren’t absorbed as well as they should be, Dr. Stein says. In this case, the nutrients are digested a little by gut bacteria, which leads to a “foul smell,” she says.
“The fat and oil tends to float to the surface of the water—because oil and water don't mix and oil and fat are lighter than the water,” Dr. Stein explains.
Nutrient intolerance: Having a lactose intolerance or other intolerance to certain nutrients can also cause floating poop, Dr. Stein says. “The rapid transit doesn't provide enough time for the enzymes to work on the food and the same types of fatty floating stools happen—usually without an oily sheen,” she says.
Olestra: Eating a lot of olestra, which is a fat substitute in some potato chips and other products, can also cause poop to float, Dr. Stein adds. “This is a deliberately designed non-absorbable fat, and it will cause this type of oily, watery stool,” she says.
Giardia: Something else to consider: The parasite giardia, which can be picked up from drinking from freshwater lakes and streams, can also cause foul-smelling, greasy poop that floats, per the Centers for Disease Control and Prevention.
Possible cancer symptom: While unlikely the cause of your floating poop, it’s important to mention that floating, greasy BMs may also be a symptom of pancreatic cancer, the American Cancer Society says. It may also be a sign of colon cancer, Stein says.
How common is this?
In general, it’s more common for poop to sink instead of float, Dr. Bedford says. Exactly how common floating BMs are is tough to say for sure, though. A 1972 study published in The New England Journal of Medicine looked at the poop of 33 healthy subjects, and found that nine had poop that floated, while 24 had poop that sank. But this is an old study that was small, making it hard to take too much away from it.
As for potential causes of health conditions and illnesses that may impact your poop, it varies. “It’s relatively uncommon to get pancreatic enzyme deficiency,” Dr. Stein says. “It’s very common to experience lactose intolerance. Giardia sometimes happens.”
When should you see a doctor?
If your poop floats once or twice and this isn’t a consistent thing for you, Dr. Bedford says it’s probably related to your diet. But if this is regularly happening for you, Dr. Stein recommends that you check in with your primary care physician.
“If you have a change in bowel habits, your doctor will ask for a sample of stool to be sent to the lab to check for infections or other causes,” Dr. Stein says. “If you continue to experience symptoms beyond a few weeks, a colonoscopy with biopsies may be recommended to make sure there are no concerns for colitis (inflammation of the colon), cancer (colon cancer), or other issues that could be contributing to your symptoms.”
Is there anything you can do about poop that floats?
There’s nothing about floating poop on its own that’s harmful. But if you notice you’re regularly having floaters, it’s a good idea to talk to your doctor to make sure you’re not dealing with an underlying health condition. They can help determine the likely cause and, from there, can suggest a personalized solution.
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