Poop is normally brown in color. This is due to the processes and chemical reactions that take place in your gut when your food is digested.

A variety of factors, such as health conditions, some types of foods, and certain medications, can change the color of your poop.

In this article, we’ll help explain why poop is usually brown, what can cause it to be a different color, and when this may be a sign of a health issue.

What makes poop brown?

About 75 percent of your poop is made up of water. The remaining 25 percent is a mixture of

• undigested carbohydrates and fiber
• fat
• protein
• bacteria
• mucus
• old red blood cells
• secretions from your intestines
• chemicals from your liver, including bile

Poop’s brown color is mostly due to bile and bilirubin.

Bile, which has a yellowish-green color, plays many roles in your digestion process. Your liver makes about 500 to 600 milliliters of bile every day, which is stored in your gallbladder.

When you eat, your gallbladder contracts, to send bile into your duodenum, the first part of your small intestine. One of the main jobs of bile is to break down fats from the foods you eat.

Another factor that contributes to poop’s brown color is bilirubin. This is a yellow-colored substance in your blood. It forms after red blood cells break down and are excreted through your liver and gallbladder and into your digestive tract.

When you mix your digested food with yellowish-green bile and yellow-colored bilirubin, the result is brown. It can range from dark brown to a pale brown. But sometimes, for a variety of reasons, poop can be a different color.

What can cause poop to be other colors besides brown?

Most shades of brown, even a greenish-brown, are considered normal and healthy for poop. The shades of brown can vary from one day to the next, based on the foods you eat and the amount of bile in your system.

But if your poop’s color is significantly different than it’s normal brown, it could also be caused by a health condition or medications. Let’s look at what the different colors could mean.

Green

Green poop can be the result of several causes. For example, eating a lot of dark green vegetables, such as broccoli or kale, can result in greenish-colored poop. There’s no health issue or cause for concern in this case.

Other causes of green poop may be due to:

• Antibiotics. Antibiotics may kill the bacteria that help turn your poop brown. This is usually a temporary condition. Once you’re off the medications, your poop should return to its normal color.
• Bacterial infections. Some bacteria, such as salmonella, that don’t usually reside in your gut, can change the color of your poop from brown to green or other colors. Viral infections and parasites can do the same thing. With a serious infection, you’ll have other symptoms too, such as abdominal pain, fever, or diarrhea.
• Gastrointestinal disorders. Conditions such as Crohn’s disease and celiac disease can cause green poop, depending on what you’ve been eating.

Black

When your poop turns black, it could be a sign that there’s bleeding in the upper portion of your digestive tract. This could be due to a stomach ulcer or some other bleeding issue. Blood mixing with bile and other digestive fluids can make your poop black and tarry.

Less serious causes of black poop could be due to:

• taking iron supplements
• eating large quantities of black or dark food, like licorice
• taking Pepto Bismol, which contains the active ingredient bismuth subsalicylate that’s known to cause poop to be black or grayish in color

If you have repeated bowel movements of black, tarry poop, it’s important that you follow up with your doctor as soon as possible.

Yellow

Yellow poop can have many causes. Disorders that affect your liver, gallbladder, or pancreas can all play a role in yellow poop. That’s because conditions that affect these organs can interfere with the amount of bile that’s used for digestion.

In infants, yellow poop can also be a sign that digestion is moving too fast, and not all the fat from food is being absorbed by the body.

Other potential causes of yellow poop include:

• celiac disease
• orange or yellow foods in your diet
• stress, which can speed up the digestive process

Red

The sight of red poop can be especially alarming.

If you’re experiencing diarrhea and your poop is red, it could be a sign that you have a viral or bacterial infection, like an E. coli infection, or rotavirus, which is sometimes called the stomach flu, or a stomach bug.

Red poop may also be the result of bleeding in the lower part of your digestive tract. This could be due to:

• diverticulosis
• inflammatory bowel disease
• colonic polyps
• hemorrhoids
• anal fissures
• intestinal infection

Food coloring, like that found in fruit punch, red candy, or Jell-O, may also turn poop red temporarily.

Pale or gray

Pale poop or clay-colored poop is typically a sign that your body isn’t producing healthy levels of bile. It could also be a sign that there are blockages in the bile ducts of your gallbladder, liver or pancreas. This could be due to conditions such as:

• biliary cirrhosis
• cholangitis
• structural defects in your biliary system

Pale or clay-colored poop can also be a warning sign of:

• viral hepatitis
• alcoholic hepatitis
• gallstones
• cysts or tumors in the biliary system

Medications, such as nonsteroidal anti-inflammatory drugs (NSAIDs), birth control pills, some antibiotics, and anabolic steroids may also cause your poop to be a pale color.

What makes poop smelly?

Bacteria and the waste products that collect in your intestines during digestion cause poop to have a smell. But the foods you eat, especially those that are high in sulfur, can also contribute to the odor and make it worse.

Some examples of high-sulfur foods include:

• meat
• garlic
• dairy
• broccoli
• cabbage

When poop smells especially foul, it may be an indication of an underlying issue such as:

• a bacterial or viral infection
• celiac disease
• inflammatory bowel diseases such as Crohn’s disease or ulcerative colitis
• chronic pancreatitis
• cystic fibrosis
• food allergies
• dairy protein intolerance

Taking antibiotics or too much of a certain vitamin or multivitamin may also cause foul-smelling poop.