Non-nutritional effects of food: an underutilized and understudied therapeutic tool in chronic gastrointestinal diseases.

The use of diet has traditionally been used to improve the nutrition of patients. However, diet also can be utilized to modify disease processes and manage symptoms independently of its nutritional role. There are few chronic gastrointestinal conditions where dietary modification is utilized therapeutically and backed by a high degree of evidence. This is not due to a lack of ideas but is more likely to lie in the difficulties associated with translating those ideas into evidence-based practice. Long lead-in times and low incidence hinders interventional studies of prevention for many conditions. The design and execution of dietary clinical trials is challenging and funding them even more so. The knowledge base of doctors in nutrition and food composition is often poor, and attitudes toward the success of and adherence to dietary therapies create additional problems. However, ideas can be successfully translated into evidence-based practice, as exemplified but the low fermentable, oligo-, di-, and mono-saccharides and polyols (FODMAP) (poorly-absorbed short-chain carbohydrates) diet for patients with functional bowel symptoms. Showing efficacy is, however, insufficient for non-nutritional dietary manipulations. Adverse effects, such as nutritional adequacy of the diet and effect on pathogenesis of other diseases, must also be carefully addressed. The physiological principles upon which the diet is based should be matched to the physiology associated with the condition being targeted, as it can be hazardous to extrapolate findings in healthy persons. There is a need for greater attention to the evaluation of dietary therapies for many chronic gastrointestinal disorders.