When undigested food in the stool is accompanied by another change in bowel habits, weight loss, or diarrhea, this may signal an underlying condition that needs medical attention.

In this article, we look at the various causes for undigested food to appear in stool and when a person should see their doctor.

Everyday causes

There are some reasons why food might not be completely digested that do not cause concern.

High-fiber foods

Fiber refers to the indigestible part of plant foods.

When a person eats high-fiber foods, it is common for some undigested material to appear in the stool because the body cannot fully break down the tough material.

Fiber also speeds up a person’s bowel movements by adding bulk to the stool, which encourages the intestinal walls to move. This movement pushes food through the digestive tract.

If food moves too quickly through the digestive system, it is more likely that some foods will be less fully digested.

Certain foods are more likely than others to be partially digested and appear in the stool. These foods include:

  • beans
  • seeds
  • corn
  • peas
  • vegetable skins
  • leafy greens
  • certain grains
  • carrots
  • raisins
  • nuts

Food such as corn is a common offender. Corn has an outer shell made of an indigestible material called cellulose. The body digests the material on the inside of the corn and expels the hard outer casing in the stool.

A person who notices a lot of undigested food in their stool should not worry most of the time, as it is likely to be due to undigested fiber or eating too quickly.

If someone notices the following symptoms plus undigested food in their stool, they should see their doctor:

  • unexplained weight loss
  • blood in stool
  • changes in bowel habits
  • loss of control of bowels
  • chronic diarrhea
  • persistent abdominal pain or cramping
  • persistent bloating or gas

If a doctor suspects that a person has a digestive system condition, they may order the following diagnostic tests:

  • a stool sample to look for blood and other abnormalities in the stool
  • blood tests to look for nutritional deficiencies or inflammation markers
  • endoscopy to look inside the upper digestive tract
  • colonoscopy to examine the lower gastrointestinal tract
  • biopsy to check for microscopic inflammation


Most of the time, seeing undigested food in the stool is not a cause for concern. It may be the result of eating too fast or eating food with a high-fiber content.

In situations where a person has other symptoms, including abdominal pain, weight loss, or changes in bowel habits and movements, they may have an underlying medical condition.

A person who is concerned about certain symptoms or a change in their bowel movements should see a doctor to find out the cause.

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