Chronic Diarrhea: Diagnosis and Management

Lawrence R. Schiller; Darrell S. Pardi; Joseph H. Sellin


Clin Gastroenterol Hepatol. 2017;15(2):182-193. 

In This Article

What Is the Role of Diet in the Pathogenesis of Chronic Diarrhea?


6. Specific dietary components may cause or aggravate chronic diarrhea. A careful dietary history is essential. (1a)

7. True food allergies are rare causes of chronic diarrhea in adults. (2b)

Specific foods and diets are often incriminated as causes of diarrhea, some with good evidence and others less so.[20] In considering associations with foods, one must consider (1) substances that in sufficient quantities cause diarrhea in a normal gut (eg, fructose), (2) foods that cause diarrhea because of an underlying condition (eg, dairy products in lactase deficiency), (3) gut alterations that limit digestion or absorption (eg, short bowel, pancreatic insufficiency), and (4) idiosyncratic food intolerances. The identification of a dietary cause of diarrhea may be facilitated by a food diary.

Poorly absorbed carbohydrates are commonly linked to diarrhea.[20] For example, fructose is absorbed by facilitated diffusion with limited capacity; when the amount ingested exceeds that capacity, malabsorption and diarrhea may occur. Disaccharides must be split by disaccharidases such as sucrase or lactase, which may be insufficient because of mucosal disease or genetic downregulation. Unabsorbed carbohydrates lead to osmotic retention of fluid in the intestine and bacteria fermentation to gases. Therefore, flatus and bloating are important clues suggesting carbohydrate malabsorption. For many clinicians, concurrent diarrhea and bloating are taken as evidence of IBS, missing the opportunity to diagnose diet-induced diarrhea.

Lactose is a common cause of diet-induced diarrhea.[21] Worldwide, most adults are lactose-intolerant and learn to avoid dairy products. Inadvertent lactose ingestion can occur from commercial foods fortified with milk. Lactose intolerance also can develop if the mucosa is diseased or bypassed.

Fructose is found in certain fruits, and it is difficult to exceed absorptive capacity with natural foods. However, high fructose corn syrup is widely used as a sweetener in processed foods and soft drinks, leading to a striking increase in fructose intake,[22] which makes it easier to exceed the absorptive capacity of the gut.

Sugar alcohol malabsorption also is increasingly recognized as a cause of diarrhea. Sorbitol, mannitol, and xylitol are poorly absorbed non-nutritive sweeteners in items such as "sugar-free" chewing gum and candy; excessive intake may cause diarrhea.[23]

The recognition that these carbohydrates can cause diarrhea and other symptoms led to development of the Fermentable Oligosaccharides, Disaccharides Monosaccharides and Polyols (FODMAP) diet.[24] In a randomized trial, a FODMAP diet alleviated intestinal symptoms in 75% of IBS patients.[25]

It is important to carefully quantify the amount of caffeine consumed in coffee and energy drinks.[26]

Gluten Intolerance. The diagnosis of CD is based on symptoms, serology, and intestinal histology.[27] It has become clear that CD can present with a wider range of symptoms than previously appreciated. Recently, it has been recognized that "gluten responsive symptoms" can be present in the absence of positive serologies or with less severe pathologic criteria (Marsh 1/2).[28] Non-celiac gluten sensitivity requires additional research, but it seems likely that gluten-free diets may benefit a broader segment of the population than previously thought. Most patients with chronic diarrhea should be screened for CD. It is less clear when a gluten-free diet should be tried in patients with diarrhea who do not have CD.[29]

Fatty and fried foods frequently are implicated in the pathogenesis of diarrhea and other symptoms.[30] Although fat malabsorption stimulates colonic secretion to cause diarrhea,[31] it seems that fat may precipitate symptoms without demonstrable steatorrhea.

Food allergies are immune reactions that may cause diarrhea and other symptoms. Food intolerances are not immune-based and are more common.[32] Epidemiologic studies suggest that 1%–2% of adults have bona fide food allergy.[33] The frequency in children is higher.[34] Certain foods more frequently trigger allergic reactions. Recent studies have linked banana, avocado, walnut, and kiwi to a latex–food allergy syndrome.[35] Although true food allergy is uncommon in adults, it should be considered when other allergic features are present such as hives. Some food-allergic patients have elevated tryptase and eosinophilic cationic protein; however, fecal calprotectin is not elevated.[33,36]