Causes of Diarrhea After Eating

Having diarrhea right after you eat is called postprandial diarrhea. You might experience this for a few days, in which case it is acute, or it may be a chronic condition that you deal with for a long time.

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 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.

Diarrhea after you eat can be caused by many things, ranging from the stomach flu to a more serious disease. It's important to bring any new or ongoing digestive symptoms like this to your doctor's attention so that you be evaluated and can get any treatment you need.

This article discusses several reasons why you may be having diarrhea after you eat. It also provides some steps you can take to feel better and possibly prevent more bouts of diarrhea after eating in the future.

Acute Diarrhea After Meals

Acute diarrhea is a common problem that typically resolves on its own after one or two days.

The simple act of eating causes the muscles in your large intestine to contract and empty your bowels. When you have an infection, food poisoning, irritable bowel syndrome (IBS), or another underlying condition, these contractions may be stronger and more painful than usual.

Stronger contractions may also cause you to feel that you urgently need to empty your bowels.

Causes

Possible causes of acute diarrhea include:

• Bacterial infections, such as Salmonella or E. coli
• Food poisoning
• Viral infections, also known as the "stomach flu"
• Parasites, such as Giardia
• Medications such as antacids, antibiotics, and chemotherapy
• Lactose intolerance, which 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

Follow these tips when you have a bout of diarrhea after eating:

• Stay hydrated. Your body doesn't absorb fluids and minerals when you have diarrhea because of how quickly stool is passing through your system. Make sure to drink extra water, clear fruit juice, or broth to replace these fluids.
• Don't rush to use an over-the-counter diarrhea product such as Imodium (loperamide) or Kaopectate (bismuth subsalicylate). These products should not be used if you have a fever or there is mucus or blood in your stools. Pepto Bismol (bismuth subsalicylate) may be an option, but check with your doctor first. None of these medications should be given to children without their pediatrician's approval.
• Choose foods wisely and only eat small meals. Stick with easily digested foods while you still have symptoms. Avoid foods that can worsen diarrhea, like dairy products, fatty foods, and foods that give you gas.

When to Call Your Doctor

Call your doctor immediately if you notice any of the following:

• Blood in your stools
• Dehydration symptoms including decreased urine, dry mouth, sunken eyes
• Fever above 100 degrees F or that lasts more than three days
• Severe stomach pain
• Diarrhea that doesn't get better within two days for an infant or child, and five days for an adult

Get medical attention right away if you develop rectal bleeding, vomiting, lack of appetite, significant weight loss, fever, anemia, abdominal pain or cramping at night.

Chronic Diarrhea

Chronic diarrhea after meals may be due to a wide variety of health problems. If you have one of the following disorders, simply eating a meal may trigger diarrhea episodes.

Common Causes

The following chronic conditions can cause you to have ongoing diarrhea:

Infection

As with acute diarrhea, there are infections that can cause chronic diarrhea. These include Giardia lamblia, strongyloidiasis, and amoeba.

Lactose Intolerance

People who have lactose intolerance lack sufficient amounts of the enzyme needed to break down lactose, a sugar found in milk and milk products. This can cause diarrhea after consuming dairy foods.

Sugar Malabsorption

Along with 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 and artificial sweeteners.

Celiac Disease

People who have celiac disease experience an immune reaction to gluten, a protein found in wheat, rye, and barley.

Diarrhea from celiac disease is often extra smelly, and stool may be more likely to float rather than sink.

Inflammatory Bowel Disease (IBD)

The two forms of IBD—Crohn's disease and ulcerative colitis—can both cause diarrhea after eating.

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.

Irritable Bowel Syndrome (IBS)

IBS can also cause chronic cases of diarrhea after eating.

Bile Acid Diarrhea (BAD)

Researchers are starting to find evidence that some people who are diagnosed with IBS actually have BAD.

Your gallbladder secretes bile acids so that your digestive system can digest fats. When these acids are not reabsorbed properly, they trigger contractions in your large intestine, resulting in diarrhea.

Sometimes the cause of BAD is unknown; other times it starts after surgery or illness involving your gallbladder, pancreas, small intestine, or another digestive organ.

Gallbladder Removal

Without a gallbladder, some people have a problem with their small and large intestines not regulating bile acids as well as they should. This can cause similar symptoms as BAD, which usually resolve quickly after the surgery, though for some people it remains an ongoing problem.

Dumping Syndrome

This syndrome is most common among people who have had bariatric surgery for weight loss.

Dumping syndrome is also known as rapid gastric emptying because the stomach contents empty too quickly into the small intestine.

Eating can trigger diarrhea, especially when meals have a high sugar content.

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 measures the amount of fat in stools, some researchers theorize that the test may not be accurate in detecting mild insufficiency that causes diarrhea after eating.

Research in this area is quite limited, but one study showed that IBS-D patients who were given pancrelipase, a form of pancreatic digestive enzymes, had less episodes of diarrhea after eating.

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 may be associated with 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 Diarrhea After Eating

Follow these tips if you have ongoing problems with diarrhea after eating:

• Tell your doctor. Any unusual symptom should always be brought to their attention so that you get a proper diagnosis and a helpful treatment plan.
• 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 make your intestinal contractions stronger and 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. Both deep-breathing exercises and progressive muscle relaxation—strategic tensing and relaxing of muscles throughout the body—can be effective in calming your body. They may also help slow the emptying of your bowels.

Theories on Postprandial Diarrhea Syndrome in IBS

Studies on postprandial diarrhea are quite limited, but researchers have the following theories about what is going on in the bodies of people with IBS-D.

Postprandial Diarrhea Syndrome

Two IBS researchers—Mary Money, MD, and Michael Camilleri, MD—have proposed three possible causes for what they call postprandial diarrhea syndrome. All of them are often misdiagnosed as IBS-D: 

• Bile acid malabsorption (BAM), in which your intestines don't absorb bile acids like they should
• Pancreatic exocrine insufficiency, in which your pancreas doesn't make enough digestive enzymes
• Glucosidase deficiency, in which your small intestine does not make enough of the enzyme glucosidase, which breaks down sugars and carbohydrates

They acknowledge that these disorders are hard to identify, but that the diagnosis can often be confirmed if a patient responds well to treatment.

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 people with IBS-D who took GERD medications had significantly less symptoms of postprandial diarrhea. More research is needed to confirm these results.

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. What they do have passes through to the large intestine quicker than normal, which may contribute to postprandial diarrhea.

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 theories explaining the problem, data regarding treatments for this condition don't exist, so it's unclear which treatments will help patients, and which do not.

But if this is true, the development of medications that would slow transit time, and thus better regulate the flow of liquid into the large intestine, may be helpful.

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 doctor to see if any particular treatments would be a safe option for you.

Summary

Diarrhea shortly after eating—known as postprandial diarrhea—can be acute, meaning that it resolves on its own after a few days, or it can be a chronic, ongoing problem. If you've had diarrhea for more than five days, it's time to see your doctor.

Acute postprandial diarrhea is often caused by a transient illness like the stomach flu or food poisoning. When it's ongoing, postprandial diarrhea might be a symptom of a chronic illness like lactose intolerance, IBS, or celiac disease.

If you are suddenly having diarrhea after you eat, drink lots of water to stay hydrated, eat small meals, and be on the lookout for more concerning symptoms like dehydration or blood in your stools, which require urgent medical attention.

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 the fear of needing to rush to the restroom.