Tummy Troubles: Finding the Cause

At one time or another most people have been waylaid by a gassy, bloated feeling, often accompanied by a decidedly uncomfortable loose stool experience. But why? What actually causes a runaway stomach and uncooperative bowels?

​Read more:​ Decoding Your Gut: The Ultimate Guide to the Microbiome, Digestive Issues and More

According to the Mayo Clinic, most stomach gas arises from the air you swallow when you consume food or beverages. Eating too quickly, drinking through a straw and talking while chewing can all up gas levels. Still, most of that gas is exhaled by burping.

Gas-driven bloating and pain can occur when the digestive system is unable to sufficiently break down or absorb certain foods, the Mayo Clinic notes.

A variety of foods can give rise to gas and loose stool, says Connie Diekman, MEd, RD, a St. Louis-based food and nutrition consultant and former president of the Academy of Nutrition and Dietetics. "Gas-forming foods include beans, sulfur-containing vegetables like cabbage, Brussels sprouts, broccoli, cauliflower and kale," she notes. Milk, sugar and lactose can also trigger gas in some people, she adds.

Gas and stool problems related to lactose may reflect lactose intolerance, says the Mayo Clinic. With that condition, a deficiency in levels of the small intestine enzyme called lactase makes eating any dairy food problematic.

And to the list of foods that can cause stomach troubles. add "anything high in fiber," says Lona Sandon, PhD, RDN, director of Master of Clinical Nutrition Coordinated Program and associate professor of clinical nutrition at the School of Health Professions, University of Texas Southwestern Medical Center at Dallas. That's true "especially if someone is not used to eating a lot of fiber," she says.

The Mayo Clinic notes that beans, peas, and whole grains are examples of high-fiber foods, alongside fruits and vegetables. Fiber supplements that contain psyllium, such as Metamucil, can also increase gas in the large intestine.

Other dietary sources of gas include soda and beer, the Mayo Clinic says, as well as artificial sweeteners like sorbitol, mannitol and xylitol.

"In terms of loose stool, high fat and/or fried foods, milk, sugar, spicy foods and caffeine can all be triggers," explains Diekman, also the author of ​The Everything Mediterranean Diet Book​ and former director of university nutrition at Washington University in St. Louis.

To that list, the Mayo Clinic adds fructose, a sugar naturally found in fruit and honey.

"Yes, in some people, fruit sugar — meaning fructose — can also lead to loose stools," Diekman says. "It is also possible for too much fruit or too many vegetables at one time to trigger loose stools."

​Read more:​ Poops a Little Loose? Here Are 5 Foods That Can Make Diarrhea Worse (and 3 That'll Help)

Another cause of bloating and loose stools can be traveler's diarrhea — the most common travel disease afflicting Americans, according to the Centers for Disease Control and Prevention (CDC). While usually not serious, the bloating and diarrhea that ensues is not fun, either.

"Traveler's diarrhea is diarrhea that occurs after consuming food or water that contains bacteria that our body tries to fight off," Diekman explains.

The risk, Sandon says, stems from the fact that "many other countries do not abide by the same food safety practices as the U.S." Because of that, she says, traveler's diarrhea is typically the "result of drinking unclean water or a food-borne illness related to not cooking food thoroughly or poor food safety practices." Those, she notes, include not washing hands before, during or after preparing food and handling raw foods.

On the other hand, sometimes the cause is exposure to bacteria that "is foreign to our digestive tracts, triggering a reaction to eliminate the bacteria," Diekman says. An example is the raw cheeses commonly found across Europe. "Since Americans do not consume them regularly, we often react to the foreign bacteria," she notes.

Treatment for mild cases typically centers on rest and rehydration, notes the CDC. In more serious cases, antibiotics may be required.

Several chronic intestinal illnesses can also give rise to gas and stool issues. Those, says Mayo Clinic, include diverticulitis, ulcerative colitis and Crohn's disease.

Another source of bloating, diarrhea and abdominal pain can be pancreatic insufficiency, in which another small intestine enzyme, key to proper food absorption, is lacking. According to the Medical University of South Carolina, this condition often sources back to chronic pancreatitis.