IBS and Diarrhea After Eating

Postprandial Diarrhea Syndrome Proposed

Woman suffering from abdominal pain, France

Have you noticed that you are more likely to experience diarrhea episodes after you eat? This type of diarrhea is called postprandial. In general, this symptom is attributed to the fact that the act of eating prompts colon movement. Thus the traditional recommendation is to eat small, low-fat meals to minimize the activation of the colon.

However, 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.

Possible Causes of Diarrhea After Eating

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":

Support for the theory: A recent 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 work-up of all IBS-D patients.  The following article provides a deeper discussion of the role of BAM in IBS:  I-BAM and IBS-D. 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: Drs. Money and Camilleri theorize that patients with postprandial diarrhea could benefit from pancralipase (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: Drs. Money and Camilleri propose that amalase, 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 more recent 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

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. See more about Diarrhea After Eating.


Dave, B. & Rubin, W. "Inhibition of Gastric Secretion Relieves Diarrhea and Postprandial Urgency Associated with Irritable Bowel Syndrome or Functional Diarrhea" Digestive Diseases and Sciences 1999 1893-1898.

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.

Monnikes, H., et.al. "Randomised Clinical Trial: Sustained Response to PPI Treatment of Symptoms Resembling Functional Dyspepsia and Irritable Bowel Syndrome in Patients Suffering From an Overlap with Erosive Gastro-oesophageal Reflux Disease" Alimentary Pharmacology and Therapeutics 2012 35:1279-1289.

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