Causes of Diarrhea After Eating

Experiencing diarrhea right after you eat is known as postprandial diarrhea. It may just have started occurring, in which case it is acute, or you may have had 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. 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 (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)
Irritable bowel syndrome with predominant diarrhea (IBS-D), which may also be a chronic cause

What to Do For Acute Diarrhea

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.
Don't rush to use an over-the-counter diarrhea product such as Imodium or Kaopectate. These products should not be used if you have a fever or there is mucus or blood in your 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.
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 including 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. These include rectal bleeding, vomiting, lack of appetite, significant weight loss, fever, abdominal pain and cramping at night, and anemia.

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. Addressing the underlying illness can help to bring about relief from the symptom of running to the bathroom after meals.

Infection: As with acute diarrhea, there are infections that can cause chronic diarrhea. These include Clostridium difficile, Giardia lamblia, and amoeba.
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 this symptom usually resolves itself quickly after the surgery date, for some people 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 and you should be screened for this disease if you are experiencing chronic diarrhea after eating.

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 can trigger symptoms such as diarrhea, especially eating meals with high sugar content.
Microscopic colitis: This type of colitis is a distinctly different illness than ulcerative colitis. With microscopic colitis, inflammation of 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.
Pancreatic Exocrine Insufficiency: In this condition, the pancreas does not produce enough digestive enzymes to fully digest the foods that you eat. 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. Research in this area is quite limited. A review found one study that showed a small percentage of IBS-D patients do suffer from pancreatic exocrine insufficiency. In another small study, IBS-D patients who were given pancrelipase, a form of pancreatic digestive enzymes, reported a reduction in episodes of postprandial diarrhea.

What to Do for Chronic Problems With Diarrhea After Eating

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.
Follow your doctor's orders to best manage your underlying health problem.
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.
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. Many people deal with a lot of stress in their 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). Research on postprandial diarrhea is quite limited. Here are avenues that preliminary research has identified:

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 positive response to treatment of the theorized problem might serve as confirmation of the diagnosis. They believe three diagnoses should be considered: bile acid malabsorption (BAM), pancreatic exocrine insufficiency, and glucosidase deficiency.
Excessive Gastric Acid: Excessive amounts of gastric acid have long been associated with the development of gastroesophageal reflux disease (GERD). A small study found that GERD medications given to a group of IBS-D patients resulted in a significant decrease in symptoms of diarrhea and postprandial urgency. However, this finding has not been replicated.
Small Bowel Water Content: A group of researchers found that, compared to healthy control subjects, IBS-D patients have lower amounts of water in the small intestine and it passes through quicker to the large intestine, which may contribute to postprandial diarrhea. This research dovetails with the FODMAPs theory for IBS as foods with high osmotic value (meaning they produce higher volumes of fluid) are particularly troublesome for people with IBS. If true, the development of medications that would slow transit time and thus better regulate the flow of liquid into the large intestine may be of value.

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

When diarrhea 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.