Undigested Food In Stool: Causes

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A healthy body will consume food and eliminate waste products through stool and urine.

Sometimes however, bodies may not digest food correctly and this undigested food could end up in our stool. 

This can often leave us confused or panicked, but there are some explainable and rational reasons for undigested food in stool, such as diarrhea or irritable bowel syndrome. 

Causes Of Undigested Food In Stool 

Although there are a variety of reasons for undigested food in stool, perhaps the most common reason is consuming food full of fiber.

Fiber is fantastic for healthy stool as it bulks the stool (and is a fantastic help for those struggling to poop)!

That’s because stool with more bulk will make the wall of the intestines contract, effectively pushing food downstream to further aid digestion and expulsion. 

Fibrous food usually does not get digested entirely like other foods. One example of this is corn – you may have experienced this before or seen it in a movie – that there’s corn in the poop! Other foods full of fiber that don’t get digested can be: 

  • Seeds (such as sesame) 
  • Peas 
  • Grains (like quinoa) 
  • Beans 
  • Tomato skins and other vegetable skins 

Some of these foods have other reasons for their “refusal” to be digested in the same way.

Corn for example has an outer layer which does not get digested easily, due to its outside containing cellulose.

We cannot digest cellulose but we can digest everything else that corn has to offer! Weird right?

If I’m Seeing Corn In My Poop – Do I Need To Worry?!

It isn’t normally something to panic about. The fact is, our bodies don’t digest everything and certainly cannot break all fibrous foods entirely down.

There are ways you can assist in the breaking down of fibrous foods which might ease any worries you have. 

Steaming food or making these foods softer can help your body break them down.

Scientists debate whether or not this will increase the absorption of nutrients, but it’s something to think about if you’re concerned about this. 

If you’ve noticed that you’ve eaten corn yesterday and you already have corn in your stool – this might be due to a digestive problem as the stool is being passed faster than the usual 2-3 days from the time of ingestion. 

When Is It Time To See My Doctor?

Are you struggling to poop or noticed your stool is really hard or really dry? These could indicate problems. Always take note of how your stool appears too, as it should be brown and soft. 

There are a few problems that you should see a doctor about if you’re experiencing continuous or frequent bowel evacuation, blood in your stool, difficulty controlling your bowel habits or rapid, unexplainable weight loss. 

These symptoms might be an indicator of underlying issues far more serious than simply undigested fiber. We’re going to look at some of these serious causes and some less serious ones. 


As we said, if you’ve noticed undigested fiber (such as corn) in your stool quicker than expected, it could be due to stool passing faster than usual. One cause of this is diarrhea. 

Diarrhea is when you pass loose stool or stool more frequently than normal. It’s fairly common and normally not something to feel anxious about.

However, it can sometimes be an indicator of further problems, and diarrhea is also a problem due to its dehydrating effect on the body. 

It can be caused by a virus, a bacterial infection, spicy foods, medications, psychological issues and other problems, like bowel inflammation.

You should see a doctor if you notice the stool is changing color, with red, maroon, or black stool being a sign of possible gastrointestinal bleeding. Learn more about black specks in stool.

You should also see a doctor if you begin to feel lightheaded or very dizzy as this could be severe dehydration. 

Read more about Diarrhea After Eating Causes.

Lactose Intolerance 

Lactose intolerance is another fairly common condition.  In fact around 30 million Americans are lactose intolerant.

With lactose intolerance, the body cannot properly break down the sugar known as lactose, predominantly found in dairy products such as milk or cheese. 

Lactose intolerance can manifest itself with gastrointestinal symptoms such as bloating, excess gas or diarrhea because the lactose is not being digested properly.

This is due to the small intestine not producing the enzyme called lactase.  

If you’re producing stool quicker due to lactose intolerance, you can take steps to change your diet by eliminating dairy or using a lactase supplement like Lactaid to help get your bowel habits back to normal.

Avoid anything with lactose such as milk, ice cream or cheese. Instead, go for lactose free products. 

Irritable Bowel Syndrome 

Undigested food in your poop can be a sign of diarrhea predominant IBS.

It is difficult to know specifically, but it is a possibility, particularly if you’re showing other IBS symptoms such as abdominal cramping or pain associated with irregular bowel habits.

If your colon is sensitive, you may need to seek further help. 

Celiac Disease 

This condition is shown when your body cannot break gluten down. Gluten is found in a variety of common foods like barley, rye and wheat.

This can cause gastrointestinal issues including diarrhea and therefore can expel foods that aren’t fully digested. 

The only effective treatment for Celiac disease is a gluten free diet.

Inflammatory Bowel Disease

Crohn’s disease and ulcerative colitis are inflammatory bowel diseases which can cause abdominal pain, diarrhea, weight loss and even blood in the stool.

To diagnose inflammatory bowel disease, a colonoscopy will be done by your gastroenterologist to look at the lining of the colon and small intestine and obtain biopsies.  

There are many treatment options available for inflammatory bowel disease that are influenced by the extent and severity of disease.

Exocrine Pancreatic Insufficiency 

Your pancreas might not be producing the correct amount of enzymes to digest the food. This can occur in patients who have chronic pancreatitis or pancreatic cancer.  

A simple stool test can help determine if this condition is present.  Prescription enzyme supplements are available to help treat this condition.

Read about Pancreatitis Treatment at Home.

What Should I Do If I Recognize These Symptoms?

The bottom line is that you should always speak with your doctor or health professional when concerned about your health.

Your doctor may refer you to a gastroenterologist or other specialist for specific examinations such as stool tests, blood tests and/or colonoscopy. 

For more related articles on stool, check these out:

Written and Medically Reviewed By

  • Sheila Jennings

    Sheila Jennings is a 4th-year medical student and also freelances as a content writer on gut health, nutrition, and food. She lives with IBS and has learned how to keep her symptoms at bay through a healthy diet and exercise. She wants to educate others on what they can do to take back control of their gut health and live like they used to.

  • Julie Guider, M.D.

    Dr. Julie Guider earned her medical degree from Louisiana State University School of Medicine. She completed residency in internal medicine at the University of Virginia. She completed her general gastroenterology and advanced endoscopy fellowships at University of Texas-Houston. She is a member of several national GI societies including the AGA, ACG, and ASGE as well as state and local medical societies.