When certain poop colours are red flags, according to experts

Stock image of man on his phone sitting on the toilet with jeans around his ankles
Some poop colours can be a cause for concern. Photo credit: Getty Images

By Kristen Rogers of CNN

There isn't a one-size-fits-all answer for how often you should poop, but when it comes to what colour your stool should be, expert consensus is much narrower. And deviations from it can be a cause for concern.

"The most common colour is brown, shades of brown," said Dr Mark Corkins, division chief of paediatric gastroenterology at the University of Tennessee Health Science Center.

The brown comes from the breakdown of bilirubin, a pigment created when old blood cells break down in the liver, and bile, which is typically dark brown or green and is made by the liver to aid in fat digestion, according to McGill University's Office for Science and Society. When bilirubin and bile are secreted in the small intestine during digestion, they ultimately turn the poop brown.

This physiological process is also the reason why green is the second most common poop colour.

Green stools can mean food moved through the GI tract rapidly, so the green bile in the poop is still in its original form and hasn't broken down into brown, according to Dr Rena Yadlapati, professor of medicine in the division of gastroenterology at the University of California San Diego.

"We do see that sometimes with diarrhoea or infections," Yadlapati added. "But if there's good bulk to the stool and it's green, it's generally going to be attributed to more of the dietary factors or maybe taking some iron (supplements)."

Since poop colour is influenced by what you eat and drink as well, experts said, a good rule of thumb for determining the cause of any unusual poop colours is recalling what you ate or drank within the last 24 hours before you panic and call your doctor. Eating a lot of tomato juice, beets or red gelatin or drinking a lot of energy drinks with red dyes could make poop red, Corkins said.

Some medications and supplements can affect the colour of your poop as a side effect. But if what you've consumed likely isn't the cause, here's what you should know - and when to see a doctor.

The meaning of yellow or orange poop

Yellow or orange stools can signal excess fat, especially if they also look greasy or oily, Yadlapati said.

"Some people will note that they're associated with a bad smell, as well," she added. The colour "could indicate that there's a poor absorption of fats, and that could be from celiac disease, pancreatic conditions or certain infections."

Celiac disease is a chronic immune and digestive disorder in which eating the protein gluten - found in breads and cereals - leads to damage in the small intestine.

Young children tend to prefer orange and yellow vegetables - such as carrots - over others, so their poop might be these colours for that reason, Corkins said. "It's not dangerous," he added. "Keratin is the yellow-orange pigment in there. Beta carotene is a nutrient, but it just freaks everybody out when the stools come out yellow or orange."

When your stools are black

When patients report having black poop, "from the doctor's perspective, what we're always looking for is that tarry black look, because that's a warning sign," Yadlapati said. "That could mean that a patient is having melena."

Melena is a symptom of internal bleeding in typically the upper GI tract - the oesophagus, stomach and first part of the small bowel.

"When you lose blood from there, as the blood is travelling along the digestive tract, it turns black," Yadlapati said. "That could be from things like ulcers (or) inflammation that's leading to bleeding polyps. What we don't see as much, but what we worry about, is some type of stomach cancer."

Supplements such as iron, or diarrhoea medications with bismuth subsalicylate, can also make stools black.

White stools or lack of colour

If your poop is white or very pale, there might not be enough bile reaching your digestive tract, Yadlapati said.

"This could maybe indicate a more serious cause, like some kind of condition in the liver, the bile ducts or the pancreas," she added. "At the same time, certain medications like, for instance, barium - which is the chalky fluid that patients drink when they're getting certain X-rays - that also can change the colour of the stool to a pale white colour."

Red poop can be a red flag

Red poop is a bigger concern because "there's maybe some bleeding from lower down, so the colon or the rectum," Yadlapati said. Usually, gastroenterologists think blood in poop is coming from lower in the colon or rectum because poop red from blood would indicate the blood hasn't yet had time to change colour.

"That could be in the form of, sometimes, haemorrhoids, present with bright red blood in the toilet paper or bright red blood in the toilet bowl, but not necessarily mixed in with the stool," she added.

Other causes can include ulcers in the gastrointestinal tract produced from medications or conditions such as ulcerative colitis or Crohn's disease, or arteriovenous malformation (AVM) polyps, which are little blood vessels that tend to bleed, Yadlapati said. Colon cancer is a less common cause, but it's still a concern.

"If you have red poop because of blood in the stool, honestly, that's usually not the only symptom you're having," Corkins said. Red poop unassociated with anything you recently consumed may also come with stomach pain or fatigue.

"For all these reasons," Yadlapati said, "if you see red in the stool and it's not something that's linked with something you just ate or medications that you took, it is a reason to talk to the doctor."