What Causes Gas and Loose Stools?

Intestinal gas and loose stools often occur simultaneously with a variety of disorders and conditions. Incomplete digestion commonly leads to diarrhea. As undigested food reaches the large intestine, colonic bacteria break down the particles, producing gas. Functional disorders of the colon can also affect the consistency of stool and the production of gas. As many disorders can cause gas and loose stools, an accurate diagnosis proves pivotal in devising an effective treatment strategy.

What Causes Gas and Loose Stools? (Image: Wavebreakmedia Ltd/Wavebreak Media/Getty Images)

Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is a disorder characterized by intermittent abdominal pain, discomfort or cramps that is accompanied by gas, bloating and loose stools or constipation. An August 2014 review article published by the American College of Gastroenterology reports that IBS affects roughly 11 percent of people worldwide. The disorder disproportionately affects women.

While the triggering mechanisms that lead to IBS remain an area of active medical research, it's clear that muscular hyperactivity of the colon leads to loose stools. Certain foods may increase IBS symptoms, including caffeinated tea, coffee and soda, large meals, chocolate, alcohol, dairy products, rye, barley and wheat. Excessive stress and emotional upset may also precipitate IBS symptoms. The condition is not life-threatening and is not associated with an increased risk for ulcerative colitis, Crohn disease or colorectal cancer.

Lactose Intolerance

A low concentration of the enzyme lactase in the small intestine causes lactose intolerance. Lactose, or milk sugar, is too large to be absorbed intact by the small intestine. The enzyme lactase breaks down lactose into smaller sugar molecules, facilitating intestinal absorption. Many people experience a decrease in lactase production as they reach late adolescence and adulthood. When the amount of milk and dairy products consumed overwhelms the available lactase in the small intestine, undigested lactose causes intestinal symptoms, or lactose intolerance.

Symptoms of lactose intolerance include abdominal cramps, intestinal gas and loose stools. The condition occurs more commonly in African, Asian and Hispanic Americans compared to those of northern European descent. The disorder is uncommon in infants and young children. A bout of viral gastroenteritis, commonly known as the stomach flu, can temporarily worsen or provoke symptoms of lactose intolerance.

Pancreatic Insufficiency

Disorders that adversely affect the digestion of dietary nutrients can lead to loose stools and gas. The pancreas produces the overwhelming majority of the digestive enzymes in the intestine. Proteases, amylases and lipases break down proteins, starches and fats, respectively. Deficient production or release of pancreatic digestive enzymes leaves large quantities of undigested food in the small and large intestine. The undigested food precipitates increased amounts of intestinal gas and diarrhea.

Possible causes of pancreatic insufficiency include chronic pancreatitis, pancreatic tumors and abdominal radiation therapy. Certain inherited diseases can also cause pancreatic insufficiency, including cystic fibrosis, hemochromatosis, alpha-1-antitrypsin deficiency and Shwachman-Diamond syndrome.

Other Causes

There are several other possible causes of loose stools and gas. Incomplete digestion of sugars other than lactose can lead to gas and diarrhea. For example, excess fructose from sweetened juices or consuming large amounts of fruit can sometimes lead to these symptoms. High intake of low-calorie sweeteners called sugar alcohols, such as sorbitol and xylitol, can also cause diarrhea and gas.

Certain intestinal infections might also be responsible. For example, infection with the microscopic parasite Giardia typically causes loose, greasy stools along with excess gas and abdominal pain. Infection most commonly occurs after consuming water or food contaminated with the parasite. Overuse or abuse of laxatives might also cause diarrhea and excess gas.

Warnings and Precautions

An occasional bout of excess gas with loose stool occurs to almost everyone at some point, often due to a dietary indiscretion. If you experience these symptoms frequently, however, it's important to see your doctor for medical evaluation and treatment. Seek medical care right away if you have an existing digestive or medical condition, such as diabetes, inflammatory bowel disease or HIV/AIDS. Signs and symptoms that signal the need for urgent medical evaluation include: -- fever -- lightheadedness, dizziness or fainting -- dry mouth and/or increased thirst -- dark urine or decreased urination -- persistent vomiting -- severe or worsening abdominal pain -- greasy, bloody or tarry stools

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