Causes of diarrhea after meals


Diarrhea that occurs right after eating is known as postprandial diarrhea.

It may have just started, in which case it is acute, or you may have had it for a long time and it is a chronic condition. By learning about the common causes of post-meal diarrhea, you will be able to work with your doctor on an effective treatment plan.

Any new or persistent digestive symptoms should be brought to your doctor’s attention so that you can get an accurate diagnosis and treatment plan. Although diarrhea after meals can be the result of one of the health problems described here, it can also be a sign of other serious illnesses.
Causes of acute diarrhea after meals

Acute diarrhea is a sudden onset of diarrhea episodes. Diarrhea, regardless of the cause, can occur after eating because the simple act of eating stimulates muscle movements in the large intestine to empty the bowels. 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.

  • Bacterial infections such as Salmonella or E. coli
  • Food poisoning
  • Viral infections (commonly called “stomach flu”)
  • Parasites such as Giardia
  • Medications such as antacids, antibiotics, chemotherapy, etc.
  • Lactose intolerance (can also be a chronic cause)
  • Irritable bowel syndrome with predominant diarrhea (IBS-D), which can also be a chronic cause.

What to do in case of acute diarrhea?

  1. Stay hydrated. You will need to replace fluids and minerals that your body is not absorbing due to the rapid transit of stool through your system. Try to drink water, clear fruit juice and broth in sips.
  2. Don’t rush to take an over-the-counter diarrhea medication like Imodium or Kaopectate. These products should not be used if you have a fever or if there is mucus or blood in your stool. Pepto Bismol may be an option, but check with your doctor first. None of these medicines should be given to children without the permission of the child’s doctor.
  3. Pay attention to your diet and eat only small meals. See the lists of what to eat when you have diarrhea and what to avoid when you have diarrhea. Once the diarrhea is gone, learn to eat when you feel better.

When to call your doctor?

If you have any of the following symptoms, call your doctor immediately:

  • Blood in your stool
  • Symptoms of dehydration, including decreased urination, dry mouth, sunken eyes
  • Fever over 100 F or lasting more than three days
  • Severe stomach pain
  • Worsening symptoms of diarrhea, or if diarrhea is still present two days later in an infant or child, and five days later in an adult.
  • Know the red flag digestive symptoms, which are particularly dangerous symptoms to watch for that call for immediate medical attention. These include rectal bleeding, vomiting, lack of appetite, significant weight loss, fever, abdominal pain and cramps at night and anemia.

Causes of chronic diarrhea after eating

An ongoing problem with diarrhea after meals can be caused by a wide variety of health problems that have chronic diarrhea as a symptom. If you have one of these conditions, simply eating a meal can trigger episodes of diarrhea. Managing the underlying disease can help relieve the symptom of running to the bathroom after meals.


  • Infection: As with acute diarrhea, there are infections that can cause chronic diarrhea,5 including Clostridium difficile, Giardia lamblia and amoeba.
  • Irritable Bowel Syndrome (IBS): Eating alone may be enough to trigger the symptom of diarrhea in some people with IBS. It is not clear why the digestive system is so hyper-reactive in this disorder.
  • Bile Acid Diarrhea (BAD): Researchers are beginning to find evidence that some people diagnosed with IBS actually have BAD.6 Bile acids are secreted by the gallbladder so that your digestive system can digest fats. When these acids are not reabsorbed properly, they serve to stimulate contractions of the large intestine, causing diarrhea. Sometimes the cause of BAD is unknown; other times it occurs as a result of surgery or disease affecting your digestive organs (your gallbladder, pancreas or small intestine, for example).
  • Gallbladder removal: Without a gallbladder, some people experience a problem with poor regulation of bile acids in the small and large intestines, causing symptoms similar to BAD. Although this symptom usually resolves quickly after the procedure, for some people it remains an ongoing problem.
  • Lactose Intolerance: People who are lactose intolerant do not have enough enzymes to break down lactose, a sugar found in milk and milk products. Lactose intolerance can be identified with a breathalyzer test or an elimination diet.
  • Sugar Malabsorption: In addition to lactose, some people are unable to digest fructose and sorbitol. Fructose is present in many fruits and in high-fructose corn syrup. Sorbitol is also present in some fruits and in artificial sweeteners. Like lactose intolerance, fructose or sorbitol malabsorption can be identified by breath tests or an elimination diet.
  • Celiac Disease: People with celiac disease have an autoimmune reaction to the ingestion of gluten, a protein found in wheat, rye and barley. Diarrhea caused by celiac disease is often odorous and stool may be more likely to float rather than flow. Celiac disease has serious health consequences and you should be screened for it if you have chronic diarrhea after eating.
  • Inflammatory bowel disease (IBD): Both forms of IBD – Crohn’s disease and ulcerative colitis – can cause the symptom of diarrhea after eating.8 Unlike the health problems mentioned above, diarrhea caused by IBD can include signs of blood in the stool. Any signs of blood in the stool should be brought to your doctor’s attention immediately.
  • Dumping syndrome: This syndrome is most often experienced by people who have had bariatric surgery to lose weight. Dumping syndrome is also known as rapid gastric emptying because the contents of the stomach empty too quickly into the small intestine. Eating can trigger symptoms such as diarrhea, especially when eating high-sugar meals.
  • Microscopic colitis: This type of colitis is a very different disease from ulcerative colitis. In microscopic colitis, inflammation of the cells lining the intestines can only be seen when the tissue is examined under a microscope. The cause of microscopic colitis is not well known. Its symptoms include persistent or intermittent episodes of watery diarrhea.9
  • Colon cancer: Chronic diarrhea is not usually a sign of colon cancer (constipation may be more likely), but any change in stool frequency 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 in addition to chronic diarrhea, you should see your doctor immediately.
  • Exocrine Pancreatic Insufficiency: In this case, the pancreas does not produce enough insulin to keep the body functioning.

What to do if you have chronic diarrhea problems after eating?

  1. Talk to your doctor. Any unusual symptoms should always be brought to the attention of your doctor. This ensures that you receive a proper diagnosis and, as a result, a useful treatment plan can be developed.
  2. Follow your doctor’s instructions to better manage your underlying health problem.
  3. Eat small meals throughout the day and avoid fatty foods, such as fried foods, fatty meats and heavy gravy. Large meals and fatty foods can increase the strength of bowel contractions and thus cause an episode of diarrhea.
    Use relaxation exercises to calm your body. Because of the close connection between your brain and your gut, stress can be a trigger for diarrhea.11 Many people deal with a lot of stress in their lives, not to mention the fact that having diarrhea after meals is stressful. Deep breathing exercises and progressive muscle relaxation techniques can be effective in calming your body and therefore slowing down the emptying of your bowels.

New theories about postprandial diarrhea syndrome in IBS

New theories are emerging to suggest that something else may be going on in some patients diagnosed with diarrhea-predominant irritable bowel syndrome (IBS-D). Research on postprandial diarrhea is quite limited. Some preliminary research leads include:

  1. Postprandial diarrhea syndrome: 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 a positive response to treatment of the theorized problem could serve as confirmation of the diagnosis. They suggest that three diagnoses should be considered: bile acid malabsorption (BAM), pancreatic exocrine insufficiency and glucosidase deficiency.
  2. Excessive gastric acid: Excessive amounts of gastric acid have long been associated with the development of gastroesophageal reflux disease (GERD). One small study found that GERD medications administered to a group of IBS-D patients resulted in a significant decrease in diarrhea symptoms and postprandial urgency. However, this finding was not replicated.
  3. Small bowel water content: A group of researchers found that, compared with healthy controls, IBS-D patients have less water in the small bowel and it moves more quickly into the large bowel, which may contribute to postprandial diarrhea. This research is consistent with the FODMAPs theory for IBS because foods with high osmotic value (i.e., they produce higher volumes of fluid) are particularly problematic for people with IBS. If this is true, the development of drugs that would slow down transit time and therefore better regulate fluid flow in the large intestine could be helpful.

Research findings on postprandial diarrhea

Clearly, research into the factors that cause postprandial diarrhea in IBS is quite limited and, therefore, no definitive conclusions can be drawn. Furthermore, despite the variety of plausible theories explaining the problem, there are no treatment data for this condition, so it is not yet clear which treatments will help patients and which will not.

Hopefully, more research will lead to a better understanding of the topic and effective treatment options. In the meantime, if you tend to have episodes of urgent diarrhea after eating, discuss the topic with your doctor to see if any of the proposed interventions would be a safe option for you.


When diarrhea occurs right after eating, it becomes difficult to enjoy a meal. You may be wary of what you should eat and anxious about eating anything. You are not alone. Many people have this symptom. Work with your doctor to find the underlying cause. You may be able to find ways to enjoy your meals without fear of having to rush to the bathroom.


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