What Causes Chronic Diarrhea?

A cardinal feature of Sucrose Intolerance due to Congenital Sucrase-Isomaltase Deficiency (CSID) is chronic diarrhea. However, chronic diarrhea associated with CSID has a few unique clinical features or symptoms that may differentiate it from other causes of diarrhea.

For starters, CSID is associated with fermentation in the large intestine of undigested sucrose. During fermentation, the pH environment of the large intestine drops. Thus, the stool in individuals with CSID will be acidic, or have a low pH. Acidic diarrhea can cause a rather nasty diaper rash and excoriated buttocks in infants and toddlers. Also, diarrhea related to any form of malabsorption such as the sucrose malabsorption of CSID, has a uniquely foul odor. Finally, diarrhea related to CSID is very watery.

The connection between CSID and watery diarrhea is caused by a different mechanism than the excess intestinal gas that is caused by the gassy byproducts of fermentation in the large intestine. When undigested complex sugars such as sucrose reach the large intestine, the actual presence of the food in the large intestine attracts water from the bloodstream into the large intestine. This process of water moving from a less concentrated area into a more concentrated area is called “osmosis.” The osmotic movement of water from the bloodstream to dilute the undigested complex sugars in the large intestine is the cause of chronic diarrhea associated with CSID. Perhaps your doctor referred to your watery diarrhea as osmotic diarrhea, which is a medical term for watery diarrhea.

Usually, someone who has CSID develops watery diarrhea shortly after every meal or snack they eat that contains sucrose, including starches that contain sucrose. The medical term for this timing of a diarrheal episode is called “postprandial,” which means “after eating food.” If someone with CSID always eats foods that contain sucrose, they will have chronic diarrhea.

Foods that contain sucrose may cause watery diarrhea in individuals with CSID. Examples of commonly eaten foods that contain sucrose include:

Fruits: apples, bananas, oranges, and pineapples

Vegetables: peas, carrots, onions, and sweet potatoes

Processed foods with grains: breads, cereals, pancakes, waffles, pastries, muffins, cakes, pies, and cookies

Sweeteners: table sugar, powdered sugar, raw sugar, brown sugar, and maple syrup

Sucrose Intolerance Is More Common Than You Think