Unusual Stool Colour

The small intestine absorbs food nutrients. The waste is pushed into the large bowel where water is removed. The resulting faeces are temporarily stored in the rectum before being expelled from the body via the anus. The medical names for the expulsion of faeces include defecation and egestion. Water makes up about three quarters of faecal content, while the rest is composed of solids including undigested fibre, intestinal bacteria and dietary fats. Many illnesses and events can affect the colour and texture of faeces.

Changes in the color, consistency, and frequency of bowel movements is known as a "change in bowel habits." Most people have experienced infrequent bouts of diarrhea, constipation, or a strange discoloration of their stool at one time or another.

In some cases, an unusual stool color is harmless and can be attributed to a particular food or medication—but not always. Changes in bowel habits that persist can be a serious matter and should always be investigated by a physician. Black or red stools can indicate internal bleeding somewhere in the gastrointestinal tract.

Causes of black coloured stools (known as melena)

• acidified blood
• blood from higher in the digestive tract
• iron supplements or foods high in iron
• Pepto-Bismol or other medicines containing bismuth
• black licorice
• large amounts of spinach or other greens
• blueberries
• aspirin
• other foods dark in color such as chocolate sandwich cookies (Oreos)

Causes of red coloured stools (known as hematochezia)

• blood
• hemorrhoids
• red gelatin, popsicles, or Kool-Aid
• tomato juice or soup
• large amounts beets

Causes of pale or clay coloured stools

• lack of bile salt (bile salt gives stool its brownish color)
• antacids containing aluminum hydroxide
• barium from a recent barium enema test
• hepatitis

Causes of green stools

• large amounts of green, leafy vegetables
• green or purple artificial coloring (popsicles, Kool-Aid, gelatin)
• iron supplements
• rapid transit or decreased colonic transit time

Causes of orange colored stools

• some medications (such as beta-carotene and rifampen)
• foods high in beta-carotene: carrots, sweet potatoes, apricots, winter squash, pumpkin, cantaloupe, and mangoes

If a change in stool color cannot be attributed to a dietary reason, or is accompanied by any other symptoms (such as diarrhea, constipation, weakness, or dizziness), a doctor should be consulted. Always see your doctor if you experience changes in bowel motions that don’t resolve within a day or two. Seek urgent medical attention if your stools are bloody.