Gastrocolic Reflex: Why You Need to Poop After Eating

The gastrocolic reflex is an otherwise normal response in which you feel like pooping after eating. The reflex is natural and usually nothing to worry about. But if it is unusually strong and you have to rush to the bathroom after eating, it may be a sign of irritable bowel syndrome (IBS).

Among the clues that IBS is involved are classic signs and symptoms such as abdominal cramping, bloating, the sudden urge to have a bowel movement, and in some people, diarrhea.

This article explains what causes the gastrocolic reflex and how it differs in people with IBS. It also lists certain triggers that can cause IBS to flare and describes how the condition may be treated at home or by a healthcare provider.

What Is the Gastrocolic Reflex?

The gastrocolic reflex, also known as the gastrocolic response, is a normal physiological response that occurs soon after eating food in which the large intestine (colon) suddenly has rhythmic contractions, called peristalsis, that stimulate the urge to defecate (poop).

The aim of the gastrocolic reflex is to move the extra contents of the intestines out of the body to make room for more food in the stomach. The reflex often occurs within 15 minutes of eating.

Physiologically, the gastrocolic reflex is instigated by hormones called cholecystokinin and motilin. As you eat, the expansion of the stomach triggers the release of these hormones in the small intestine, causing a normal and perfectly natural chain of events:

• Cholecystokinin triggers the release of digestive fluids from the gallbladder and pancreas into the small intestine. While this is happening, cholecystokinin stimulates contractions to move food out of the stomach and suppresses appetite so the stomach doesn't get overfilled.
• Motilin stimulates peristalsis in the stomach and small intestine motility, causing undigested food to move into the colon. This, in turn, stimulates the urge to defecate (poop).

Any new mother has seen the gastrocolic reflex in action. This is why infants often need their diapers changed soon after nursing.

Causes of an Overactive Gastrocolic Reflex

Under normal circumstances, the gastrocolic reflex will stimulate the urge to poop, albeit gently. In some people, however, the response will be exaggerated and trigger bowel urgency (the need to poop urgently).

Conditions associated with an exaggerated gastrocolic reflex include:

• Irritable bowel syndrome (IBS): A functional gastrointestinal disorder characterized by constipation, diarrhea, or both
  
• Inflammatory bowel disease (IBD): An immune-associated disorder that causes chronic inflammation of the lower digestive tract
• Dumping syndrome: A condition in which food moves too quickly from the stomach to the small intestine, often in people who have had bariatric surgery

There are several reasons for this overactive response, some of which are interconnected.

Visceral Hypersensitivity

With respect to the gastrocolic reflex, visceral hypersensitivity occurs when nerve receptors in the colon are overly sensitive. So even when the gastrocolic reflex is otherwise normal, the movement of stool into the colon can cause violent spasms that lead to bowel urgency.

With IBD, chronic inflammation can cause extreme tenderness and sensitivity of tissues in the colon and rectum.

With IBS, visceral hypersensitivity is characteristic for reasons that are not entirely clear. Even procedures like colonoscopy are known to trigger violent bowel contraction when colon tissues are stretched and manipulated. This is especially true in people with a type of IBS known as diarrhea-predominant IBS (IBS-D).

Disturbed Release of Cholecystokinin and Motilin

For reasons that are not entirely clear, people with IBS tend to experience an excessive release of cholecystokinin and motilin while eating. This is believed to be a key cause of a disease that is also thought to involve genetics and lifestyle factors.

With respect to hormones, the nerve signals between the brain and digestive tract—called the brain-gut connection—are overreactive. They not only release excessive amounts of cholecystokinin and motilin but can also do so at inappropriate times.

With motilin especially, the release of the hormone can occur between meals, leading to sudden, severe intestinal contractions and the rapid transit of food through the gut. This, in turn, can trigger spontaneous bouts of cramping and diarrhea.

The excessive release of cholecystokinin and motilin is also thought to be involved with dumping syndrome. In people who have had bariatric surgery (used to treat obesity), the entry of food into a smaller stomach space can send signals to the brain telling it that you are overly full. The brain will respond by releasing far more hormones than are needed.

Role of the Gut Microbiome

The gut microbiome is the composition of bacteria, yeast, and other microorganisms in the digestive tract which, when balanced, aids with normal digestion. The "good" bacteria and yeast effectively control the "bad" bacteria and yeast while helping break down fiber and food and improving nerve signaling between the gut and brain.

An imbalance of microorganisms in the gut is thought to play a significant role in IBS. People with IBS typically have dysbiosis (an imbalance of microbes in the colon) that can cause chronic inflammation and visceral hypersensitivity.

On top of this, an imbalance of the microbiome in the stomach and small intestines can trigger inflammation that overexcites the brain-gut connection.

Triggers

The gastrocolic reflex is triggered by eating, but other factors can influence how strongly the contractions occur. Things that can cause these contractions to become more intense include:

• Eating a large meal
• Eating a meal that contains unhealthy saturated or trans fats
• Drinking large amounts of cold liquid at one time

In addition, people who are sensitive to lactose-containing foods or high FODMAP foods may experience symptoms after eating foods in these groups. IBS, in particular, is linked to these and other food groups.

Common food triggers for IBS symptoms include:

• Alcohol
• Fried or fatty foods
  
• Caffeinated foods, including coffee, black tea, energy drinks, and chocolate
• Spicy foods, including chilis and curries
• Cured and processed meats
• Whole milk and other whole-fat dairy
  
• Artichokes, asparagus, beets, Brussels sprouts, broccoli, cabbage, cauliflower, fennel, garlic, leeks, mushrooms, okra, onions, and peas
• Apples, pears, peaches, persimmon, plums, watermelon, nectarines, and mango
• Chickpeas, lentils, red kidney beans, and baked beans
• Baked goods, drinks, juices, and canned fruits made with high-fructose corn syrup
• Artificial sweeteners

Managing Symptoms at Home

Lifestyle changes and home remedies can help you better cope if you have IBS or any other conditions that cause an overactive gastrocolic reflex. In addition to avoiding trigger foods, you may be able to alleviate or avoid symptoms by doing the following:

• Eat smaller meals throughout the day rather than three big ones.
• Sip cold drinks rather than gulping them. Avoid drinks like slushies or frozen margaritas.
• Take a probiotic supplement or eat probiotic-rich foods like pickles, kimchi, sauerkraut, kombucha, or low-fat yogurt to help normalize your gut microbiome.
  
• Use peppermint oil (available in capsule form) before meals or sip peppermint tea after meals.
• Manage stress with yoga, breathing exercises, guided imagery, and meditation.
• Try acupuncture, which some people believe can normalize digestive function.
  

Medical Treatments

As one of the most likely causes of an overactive gastrocolic reflex, IBS often needs medical treatment to help rein in the symptoms. Generally speaking, you should see a healthcare provider if you experience IBS symptoms for three or more months even if the symptoms are relatively mild. This includes bloating, gas, cramping, or diarrhea.

There are several treatment options your healthcare provider may recommend:

• Viberzi (eluxadoline): This is an oral drug indicated for the treatment of IBS-D in adults. The recommended dose is 75 or 100 milligrams (mg) twice daily, Side effects include constipation.
• Antispasmodics: These drugs may help prevent or ease strong intestinal contractions. Options include cimetropium, Bentyl (dicyclomine), drotaverine, hyoscine, (Spasmomen) otilonium, and Dicetel (pinaverium). Constipation, dizziness, and dry mouth are common side effects.
• Xifaxin (rifaximin): This antibiotic is indicated for the treatment of adults with IBS-D. It works by altering the gut microbiome to better normalize bowel function. The recommended dose is 550 mg three times daily. Side effects include constipation, nausea, and dry mouth.
• Antidepressants: Some people find relief with tricyclic antidepressants (TCAs) or selective serotonin reuptake inhibitors (SSRIs), although the effectiveness can vary and side effects can be profound.
• Lotronex (alosetron): This is a second-line option for females with severe IBS-D symptoms. The recommended starting dose is 0.5 mg twice daily, which may be increased to 1 mg twice daily after four weeks. Common side effects include heartburn, stomach pain, and indigestion.

As IBS-D can be both triggered and aggravated by stress, psychotherapy in the form of cognitive behavior therapy (CBT) may be recommended to help you identify and avoid problematic behaviors that lead to stress and the onset of IBS symptoms.

On the other hand, the popular diarrhea drug Imodium A-D (loperamide) is not recommended for people with IBS-D. In studies, Imodium A-D was not any more or less effective in relieving IBS symptoms than a sham drug (placebo).

Summary

The gastrocolic reflex is a normal response in which you feel like having a bowel movement soon after eating. However, the reflex may be exaggerated and severe in some people, most often due to irritable bowel syndrome (IBS). Inflammatory bowel disease (IBD) and dumping syndrome are also characterized by an overactive gastrocolic reflex.

In people with IBS, an exaggerated gastrocolic response can be avoided by limiting your intake of unhealthy fat, eating smaller meals, and taking antispasmodics and other medications if symptoms are severe.