What Causes Diarrhea After Eating?

Reasons You Might Be Having Postprandial Diarrhea Frequently

Woman holding her stomach in pain
Photo: Kondoros Eva Katalin/Getty Images

Do you experience diarrhea right after you eat? This is known as postprandial diarrhea. It may just have started occurring, in which case it is acute, or you may have been experiencing it for a long time and it is a chronic condition. Learning about the common causes of diarrhea after meals will help you be able to work with your doctor on an effective treatment plan.

Any new or ongoing digestive symptom should be brought to the attention of your doctor so that you obtain an accurate diagnosis and treatment plan.

Although diarrhea after eating may be the result of one of the health conditions described here, it can also be a sign of other serious diseases.

Causes of Acute Diarrhea After Meals

Acute diarrhea is a sudden onset of diarrhea episodes. Diarrhea due to any cause may occur after eating, as the simple act of eating stimulates muscle movement within your large intestine to empty your bowels. But when you have an underlying cause such as an infection, food poisoning, or IBS, these contractions may be stronger and more painful than usual and come with a sense of urgency. These may be causes of acute diarrhea:

  • Bacterial infections, such as Salmonella or E. coli
  • Food poisoning
  • Viral infections, such as are commonly referred to as the "stomach flu"
  • Parasites, such as Giardia
  • Medications, such as antacids, antibiotics, chemotherapy
  • Lactose intolerance (may also be a chronic cause)
  • IBS-D, irritable bowel syndrome with predominant diarrhea (may also be a chronic cause)

    What to Do For Acute Diarrhea

    1. Stay hydrated: You will need to replace the fluids and minerals that your body is not absorbing due to the rapid transit of stool through your system. Try to drink water and clear fruit juice and sip broth.
    2. Don't rush to use an over-the-counter diarrhea product such as Imodium or Kaopectate. These products should not be used if you are suffering from with fever or mucus or bloody stools. Pepto Bismol may be an option but check with your doctor first. None of these medications should be given to children without permission from the child's doctor.
    1. Be careful with your diet and only eat small meals. Check the lists of what to eat when you have diarrhea and foods to avoid when you have diarrhea. After your diarrhea has passed, learn what to eat when you are feeling better.

    When to Call Your Doctor

    You should call your doctor immediately if you are experiencing any of the following symptoms:

    • Blood in your stools
    • Dehydration: Symptoms include decreased urine, dry mouth, sunken eyes
    • Fever above 100 F or that lasts more than three days
    • Severe stomach pain
    • Worsening of diarrhea symptoms, or if diarrhea is still present two days later in an infant or child, and five days later for an adult.
    • Know the red flag digestive symptoms, which are especially dangerous symptoms to watch out for that call for an immediate medical consultation.

    Causes of Chronic Diarrhea After Eating

    An ongoing problem with diarrhea after meals may be due to a wide variety of health problems that have chronic diarrhea as a symptom. If you have one of these disorders, the simple act of eating a meal may serve as a trigger for diarrhea episodes.

    As you can see, the reasons behind the symptom of diarrhea can vary widely depending on your diagnosis. Addressing the underlying illness can help to bring about relief from the symptom of running to the bathroom after meals.

    • Irritable bowel syndrome (IBS): Just the simple act of eating can be enough to set off the symptom of diarrhea in some people who have IBS. It is not clearly known why there is such a hyperreactivity of the digestive system in this disorder.
    • Bile acid diarrhea (BAD): Researchers are starting to find evidence that some people who are diagnosed with IBS actually have BAD. Bile acids are secreted by your gallbladder in order for your digestive system to digest fats. When these acids are not reabsorbed properly, they serve to stimulate contractions in your large intestine, resulting in diarrhea. Sometimes the cause of BAD is unknown; other times it occurs following surgery or illness involving your digestive organs (your gallbladder, pancreas or your small intestine, for example).
    • Gallbladder removal: Without a gallbladder, some people experience a problem with poor regulation of bile acids into the small and large intestines, causing similar symptoms as BAD. Although for most people, this symptom resolves itself quickly after the surgery date, for others it remains an ongoing problem.
    • Lactose intolerance: People who have lactose intolerance lack sufficient amounts of the enzyme necessary to break down lactose, a sugar found in milk and milk products. This can cause the symptom of diarrhea after consuming dairy foods. Lactose intolerance can be identified through the use of a breath test or an elimination diet.
    • Sugar malabsorption: In addition to lactose, some people are unable to digest the sugars fructose and sorbitol. Fructose is found in many fruits and high fructose corn syrup. Sorbitol is also found in some fruits as well as artificial sweeteners. Like lactose intolerance, fructose or sorbitol malabsorption can be identified through the use of breath testing or an elimination diet.
    • Celiac disease: People who have celiac disease experience an autoimmune reaction in response to ingesting gluten, a protein found in wheat, rye, and barley. Diarrhea from celiac disease is often odorous, and stool may be more likely to float rather than sink. Celiac disease has serious health consequences, so if you are experiencing chronic diarrhea after eating, you should speak with your doctor about being screened for the disease.
    • Inflammatory bowel disease (IBD): The two forms of IBD—Crohn's disease and ulcerative colitis—can both cause the symptom of diarrhea after eating. Unlike any of the above health problems, the diarrhea of IBD may include signs of blood in the stool. Any sign of blood in the stool needs to be immediately brought to the attention of your doctor.
    • Dumping syndrome: This syndrome is most commonly experienced by people who have undergone bariatric surgery for weight loss. Dumping syndrome is also known as rapid gastric emptying because the contents of the stomach empty too quickly into the small intestine. Eating (particularly meals with a high sugar content) can trigger symptoms such as diarrhea.
    • Microscopic colitis: This type of colitis is a distinctly different illness than ulcerative colitis. With microscopic colitis, inflammation in the cells lining the intestines can only be seen when tissue is looked at under a microscope. The cause of microscopic colitis is not well known. Its symptoms include persistent or intermittent episodes of watery diarrhea.
    • Colon cancer: Chronic diarrhea is not typically a sign of colon cancer (constipation may be more likely), however any change in the frequency of bowel movements has been associated with the presence of cancer. Other symptoms of colon cancer include blood in or on the stool, fatigue, anemia, and unexplained weight loss. If you have any of these symptoms alongside chronic diarrhea, you need to see your doctor immediately.

    What to Do for Chronic Problems with Diarrhea After Eating

    1. Tell your doctor. Any unusual symptom should always be brought to the attention of your doctor. This helps to ensure that you receive a proper diagnosis and therefore a helpful treatment plan can be developed.
    2. Follow your doctor's orders to best manage your underlying health problem.
    3. Eat small meals throughout your day and avoid fatty foods, such as fried food, fatty meats, and thick gravy. Large meals and fatty foods can increase the strength of intestinal contractions and thus prompt a diarrhea episode.
    4. Use relaxation exercises to calm your body. Due to the close connection between your brain and your gut, stress can be a trigger for diarrhea. Most of us deal with a lot of stress in our lives, not to mention the fact that having diarrhea after your meals is stressful! Both deep breathing exercises and progressive muscle relaxation skills can be effective in calming your body and therefore offer the potential for slowing down the emptying of your bowels.

    Emerging Theories on Postprandial Diarrhea Syndrome in IBS

    New theories are emerging to suggest that something else might be going on for some patients who have been diagnosed with diarrhea-predominant irritable bowel syndrome (IBS-D). This work is certainly in the preliminary phase, but these theories may open the door for some novel and effective treatments.

    Two IBS researchers, Drs. Money and Camilleri, have proposed three possible causes for what they call "postprandial diarrhea syndrome." They acknowledge that diagnostic markers are limited, and suggest that positive response to treatment of the theorized problem might serve as confirmation of the diagnosis. Here are the three diagnoses they believe should be considered:

    1. Bile Acid Malabsorption (BAM)

    • What it is: During digestion, bile acids are secreted into the small intestine, where they are responsible for the digestion of fats. It is theorized that when these bile acids are not well absorbed, excessive amounts will be flushed into the large intestine. When this happens, these acids promote fluid secretion, which can contribute to the watery stools associated with diarrhea. There are a wide variety of health problems that can cause BAM, including many of the digestive diseases, congenital defects, and post-surgery consequences.
    • Diagnosis: Although there is a procedure called the 75SeHCAT scan for diagnosing BAM, it is not available in the U.S.
    • How to treat: BAM can be addressed through the use of medications known as "bile acid binders." These include Questran (cholestyramine), WelChol (colesevelam), and Colestid (colestipol).
    • Support for the theory: A review of studies using the 75SeHCAT scan on IBS-D patients found that idiopathic BAM may not be as rare as was once thought and that a high percentage of these patients do indeed suffer from mild, moderate or severe BAM. The review authors would like to see an assessment regarding BAM included in the workup of all IBS-D patients. I-BAM and IBS-D will be an ongoing subject of research. As an aside, BAM may be what is behind the findings of Dr. Habba, who coined the term "Habba Syndrome."

    2. Pancreatic Exocrine Insufficiency

    • What it is: Pancreatic exocrine insufficiency refers to a condition in which the pancreas does not produce enough digestive enzymes to fully digest the foods that we eat.
    • Diagnosis: Although there is a test for pancreatic exocrine functioning that involves measuring the amount of fat in stools, researchers have theorized that this test may not be accurate in detecting a mild insufficiency that causes postprandial diarrhea.
    • How to treat: Money and Camilleri theorize that patients with postprandial diarrhea could benefit from pancrelipase (PES), a form of pancreatic digestive enzymes.
    • Support for the theory: Research in this area is quite limited. One study found that a small percentage of IBS-D patients do suffer from pancreatic exocrine insufficiency. In another small study, IBS-D patients who were given PES reported a reduction in episodes of postprandial diarrhea.

    3. Glucosidase Deficiency

    • What it is: Glucosidases are substances that help us to digest carbohydrates. A severe genetic form of glucosidase deficiency is a rare condition. Drs. Money and Camilleri have proposed that a more mild deficiency in the a-glucosidases, glucoamylase, maltase, isomaltase or sucrase, may result in the symptom of postprandial diarrhea. They theorize that such a deficiency may explain the difficulties that many IBS patients have with certain trigger foods.
    • Diagnosis: As of now, there is no non-invasive diagnostic test for glucosidase deficiency.
    • How to treat: Money and Camilleri propose that amylase, a component of PES, may help to increase production of glucosidases.
    • Support for the theory: To date, there is scant research as to the role that glucosidase deficiency plays in contributing to the symptoms of IBS-D.

    Other Theories on Postprandial Diarrhea

    As stated above, research on postprandial diarrhea is quite limited. Here are a couple of more avenues that preliminary research has identified:

    1. Excessive Gastric Acid

    Excessive amounts of gastric acid have long been associated with the development of gastroesophageal reflux disease (GERD), a condition which results in heartburn. A small study found that medications given to a small group of IBS-D patients for the treatment of their heartburn symptoms resulted in a significant decrease in symptoms of diarrhea and postprandial urgency.

    This finding has not been replicated, but a study did find that GERD patients who were treated with a PPI experienced a decrease in their IBS symptoms. It is unclear whether these symptoms included postprandial diarrhea.

    2. Small Bowel Water Content

    Another group of researchers has theorized that postprandial diarrhea in IBS-D patients could be related to fluid levels in the small intestine following meals. Their small study found that IBS-D patients have lower amounts of water in their small intestines—both during times of fasting and following meals—than healthy control subjects. Water also passed more quickly through the small intestine in the IBS-D patients as compared to controls. These findings led these researchers to propose that perhaps an excess of water leaving the small intestine and entering the large intestine contributes to the symptom of postprandial diarrhea.

    This research dovetails with the FODMAPs theory for IBS. As one aspect of the theory, FODMAPs researchers have identified foods that have high osmotic value, meaning they produce higher volumes of fluid, as being particularly troublesome for people with IBS. This research also opens up hope for the development of medications that would slow transit time and thus better regulate the flow of liquid into the large intestine.

    The Bottom Line on Postprandial Diarrhea Research

    Clearly, research into the factors behind postprandial diarrhea in IBS is quite limited, and therefore no definitive conclusions can be drawn. In addition, despite the variety of plausible theories explaining the problem, data regarding treatments for this condition don't exist, so it's unclear thus far which treatments will help patients, and which do not.

    Hopefully, further research will shed more light on the subject and offer some effective treatment options. In the meantime, if you tend to experience urgent diarrhea episodes after eating, discuss the subject with your physician to see if any of the proposed interventions would be a safe option for you.

    A Word From Verywell

    Diarrhea is never pleasant, and when it frequently happens right after eating, it becomes hard to enjoy a meal. You may become wary of what to eat and anxious about eating anything at all. You are not alone. Many people have this symptom. Work with your doctor to find the underlying cause. You may be able to find solutions so you can enjoy your meals without fear of needing to rush to the restroom.


    DiBaise JK, Islam RS "Bile Acids: An Underrecognized and Underappreciated Cause of Chronic Diarrhea" Practical Gastroenterology 2012 36(10):32-44

    Diarrhea. National Institute of Diabetes and Digestive and Kidney Diseases. https://www.niddk.nih.gov/health-information/digestive-diseases/diarrhea/symptoms-causes.

    Marciani, L., et.al. "Postprandial Changes in Small Bowel Water Content in Healthy Subjects and Patients With Irritable Bowel Syndrome" Gastroenterology 2010 138:469-477.

    Money M, Camilleri M. "Review: Management of Postprandial Diarrhea Syndrome" The American Journal of Medicine 2012 125:538-544.

    Wedlake L, et.al. "Systematic review: the prevalence of idiopathic bile acid malabsorption as diagnosed by SeHCAT scanning in patients with diarrhoea-predominant irritable bowel syndrome" Alimentary Pharmacology and Therapeutics 2009 30:707-717.

    Continue Reading