A person's poop can say a lot about his or her health. How often you go to the bathroom, and how much waste you expel, can indicate your general digestive health.

"The digestive tract contains more bacterial cells than there are cells in the entire body," said Dr. Jean-Pierre Raufman, a gastroenterologist at University of Maryland School of Medicine. "It's very important that our bowels work well to absorb necessary nutrients but also keep out any foods, chemicals and germs that could do us harm."

While most people probably don't want to put much thought into pooping, it's an essential body function that can tell them if something is wrong. A change in bowel movements could be due merely to a change in diet, but it could also mean the body is fighting an infection or dealing with a serious condition.

Here are five hints that your poop could be giving you about your health.

Color

Stool color is often a reflection of what you eat. While various shades of brown are considered normal, some colors like black or yellow are not.

"Black stool could indicate bleeding in the stomach or the first part of the small intestine," Raufman said.

Iron supplements can darken the stool to more of a dark green, he added. Taking bismuth-containing medicines, such as Pepto-Bismol, or eating black licorice or blueberries also may cause black stools.

Bright red stool usually suggests that blood is coming from the lower part of the digestive system, such as the large intestine, rectum or anus.

Pale white or yellow stool also can mean a problem.

"The reason why stool is brown is because of our normal production of bile," Raufman said. "If there's a problem with bile flow, that may mean a problem like cancer of the bile ducts, or pancreatic cancer or hepatitis."

Shape

A change in stool shape also could be cause for concern. Stools that are narrow and pencil-thin are thought by some experts to be a symptom of colon cancer.

"It could be a sign of obstruction in the lower part of the colon," which means the bowel is partially blocked, getting in the way of the fecal matter that is passing through, Raufman said.

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Another sign of a potential problem is soft stool. Stool that sticks to the side of the toilet bowl, or is difficult to flush, could indicate the presence of too much oil.

"Oil floats, so you'll see it in the water," Raufman said. "They look like fat droplets, which can mean the body isn't absorbing the fats properly." Diseases such as chronic pancreatitis block the body from properly absorbing fat.

Whether stool floats depends on how much gas is in it. "Generally, stool that sinks or floats don't mean there's a problem," he said.

Smell

Though the smell of poop can be rather unpleasant, smells that are particularly strange or foul shouldn't be ignored.

"It's hard to tell people that stool can smell even worse, but it can," Raufman said. "If there is a change in your stool that persists or is unusual, you should see your doctor."

Stool is made up of undigested food, bacteria, mucus and dead cells. It usually smells bad because of the bacteria and parasites, but it also can have compounds that produce an especially unpleasant smell.

"If you have blood in your stool, that usually comes with a particular strange odor," he said. "Also, stool with a lot of fat can smell particularly bad."

Reasons for a foul smell could include certain medications, having food that's been stuck in the colon for too long, or having an infection, he said.

Constipation

Dry, hard stools that are hard to eliminate are a sign of constipation. People who are constipated may have bowel movements fewer than three times a week.

Constipation is a common complaint, and most people experience it at least once in their lives. More than 4 million Americans have frequent constipation, according to the National Institute of Diabetes and Digestive and Kidney Diseases.

Constipation could be caused by a number of factors, including a poor diet, lack of exercise, certain medications, lack of fluids or various bowel disorders.

If ignored, constipation could lead to complications such as hemorrhoids or rectal bleeding. The best way to relieve symptoms is to follow a well-balanced high-fiber diet, drink plenty of water, try to exercise regularly and go to the bathroom when you feel the urge.

Diarrhea

Diarrhea happens when loose, watery stools pass through your bowels too quickly. Generally it lasts one or two days and goes away on its own.

"It's a normal way for the body to get rid of toxic substances, like bacteria or viral infections," but it also can lead to dehydration, Raufman said.

Parasites found in water and food can enter the body and disrupt the digestive system, causing diarrhea that can last several days.

Diarrhea also can suggest a more serious problem. Diarrhea that lasts for at least four weeks may be a sign of a chronic disease, such as irritable bowel syndrome or Crohn's disease.

But diarrhea also could be a sign of chewing gum that contains sugar alcohol, such Xylitol or sorbitol. Raufman said, "Someone who chews one or two packs of sugar-free gum a day could also get diarrhea."

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