What Are the Causes of Frequent Loose Stools?

Loose stools affect most people from time to time. When loose, watery stools occur frequently, it's important to investigate the cause. Sometimes this change in bowel habits is related to diet, such as a high fiber intake or poor digestion of certain types of foods. However, frequent, loose stools can also be related to infections or other health conditions. If you experience unexplained and ongoing loose stools, see your doctor to have this symptom evaluated.

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The Fiber Effect

A high fiber diet is routinely recommended for a variety of health benefits, including improved intestinal health and the prevention of constipation. However, too much fiber can be problematic, especially if the change in diet happens quickly. A significant increase in dietary fiber -- eating dramatically more fruits, vegetables or bran than usual, for example -- can at least temporarily trigger frequent, loose stools. The reason this occurs is because certain fibers stimulate the gut to secrete more water and mucus, while other types of dietary fiber form gels and increase the stool's water content. Fiber supplements or laxatives can also cause loose stools or diarrhea if the dose is too strong. If your frequent, loose stools are caused by a high fiber intake, the solution is cut back some on the offending foods, and in the future make more gradual changes to your dietary fiber intake.

The Sugar Effect

Some foods, even when consumed in small amounts, may trigger frequent, loose stools. This occurs when certain sugars -- such as lactose from milk or fructose from fruit, as well as specific short-chain sugar molecules -- including the fructans in wheat or the galactans in beans, and sugar alcohols -- found in stone fruits such as cherries or prunes and in alternative sweeteners such as sorbitol, are incompletely digested and subsequently fermented by gut bacteria. This causes fluid to be pulled into the gut, which can lead to frequent, loose stools or diarrhea. These side effects, which may also include bloating, cramping, gas and pain, are more likely to occur in people with hypersensitive guts, such as irritable bowel syndrome, or when there is abnormal intestinal motility or specific intestinal enzyme deficiencies. Management is targeted at avoiding foods that contain the poorly digested sugars, or in the case of lactose intolerance, using lactase enzyme tablets or drops to ease or prevent symptoms.

Infectious Causes

Intestinal infections are another cause of frequent, loose stools, although other symptoms, such as cramping, nausea, and watery diarrhea tend to be present. Several different types of viral infections, including norovirus and rotavirus, can lead to gastroenteritis -- an inflammation in the lining of the gastrointestinal tract which causes diarrhea. Contaminated food and water can cause a variety of bacterial infections, such as Salmonella, Shigella and E. coli, and parasitic infections such as Cryptosporidium enteritis and Giardia lamblia, which can also lead to loose stools and diarrhea. Many of these infections are temporary and go away on their own, although treatment may be needed for the severe dehydration these infections can cause, and medications are commonly needed to treat parasitic infections.

Medical Conditions

Frequent, loose stools can also be related to a medical condition. Inflammatory bowel diseases, including ulcerative colitis and Crohn disease, are characterized by recurring abdominal pain and diarrhea. Celiac disease, an autoimmune disorder, leads to loose stools or diarrhea after the intestinal lining is exposed to gluten, a protein found in wheat, barley and rye. Celiac disease may also be characterized by foul smelling, oily stools. Diarrhea or loose stools may occur after surgery on the gastrointestinal tract, as a result of poor nutrient absorption or fast stool transit. A variety of other medical conditions can lead to loose stools, and this symptom can also be a side effect of certain medications, such as antibiotics, or nutrition supplements, such as magnesium.


If your loose stools are related to diet and you suspect you have intolerance to certain foods, see your doctor for a workup and diagnosis, and ask for a referral to a dietitian who specializes in gastrointestinal disorders. If you have unexplained frequent, loose stools or diarrhea that lasts for more than 1 to 2 days, or if your symptoms are severe, contact your doctor. Seek immediate medical care if you have severe abdominal pain, blood in your stool, fever, dizziness or fainting.

Reviewed by Kay Peck, MPH RD

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