When it comes to bowel function and elimination, some people’s bodies are so precise they could stand in for the atomic clocks at NASA. For others, bowel movements are so infrequent that each one is cause for celebration. Diarrhea and constipation are opposite extremes of bowel dysfunction. Both are unpleasant and uncomfortable, and both offer important clinical insights. Occasional irregularity is not cause for immediate alarm, but chronic, severe issues are signs not only of potential digestive distress, but also offer clues to dysfunction elsewhere in the body.

Diarrhea usually refers not just to going too frequently and with urgency, but also to stool consistency being loose and liquid. Since loose, runny, urgent stools are the body’s way of quickly getting rid of something toxic (e.g., a foodborne pathogen) or something it can’t digest well (like wheat or dairy), chronic diarrhea can be considered less a problem of pathology in the bowel than simply the result of dietary factors discordant with an individual patient’s physiological tolerance.

Something currently gaining a great deal of traction as it relates to bowel function is carbohydrate malabsorption. A classic example is lactose intolerance and the associated diarrhea, gas, and bloating, but the broader category also includes FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols), which encompasses fructose and fructans, among others. Because such a wide variety of vegetables, fruits, food additives, sweeteners and sugar alcohols contain these elements, low FODMAP diets are difficult to implement, but identifying food intolerances can be so effective in relieving bowel distress that one researcher said it’s “now time that diet be considered as a major therapeutic tool in the management of patients with functional bowel disorders.” The same author stressed that, when adhered to properly, low FODMAP diets show “efficacy that outstrips that associated with pharmacological interventions.”

Beyond the burgeoning world of carbohydrate intolerance, being that the GI tract is home to the greatest percentage of immune cells in the body (as GALT, or gut-associated lymphoid tissue), it makes sense that an immune-mediated response to a food could be either cause or effect in bowel dysfunction. A study in which 88% of the participants experienced at least some degree of improvement in their IBS-D symptoms suggested that IgG-mediated reactions to trigger foods might actually be one of the potential causes of IBS-D.

Of course, not all instances of diarrhea are associated with IBS. In fact, diagnoses—or, rather, misdiagnoses­—of IBS are sometimes provided in cases where the real culprit is celiac disease. It is reasonable to suspect that the same could be true for any number of food intolerances. How many patients are diagnosed with debilitating conditions for which pharmaceutical interventions are mostly ineffective, and suffer with bowel dysfunction for years—missing important events, planning travel based on the location of nearby restrooms—when a simple elimination diet and/or food sensitivity testing could go a long way toward relieving their discomfort?

Identifying the underlying causes of diarrhea is key not only for providing symptom relief and improving quality of life, but because from a functional standpoint, long-term, chronic compromised bowel health may result in nutrient deficiencies that affect the entire body.