Digestion in the gastrointestinal tract is a highly complex process involving both mechanical forces and chemical reactions to disintegrate and metabolize food material.[1] A low residue diet is a diet that restricts the ingestion of indigestible material. The term residue refers to the indigestible content of food material that remains in the gastrointestinal tract and ultimately contributes to fecal bulking.[2] In theory, a low residue diet would result in a reduction of stool quantity and frequency. This diet includes eggs, refined grains, white rice, seafood, and poultry. Dairy intake is limited, and high fiber-containing food and whole grains are typically entirely avoided.[3]

The main issue of concern results from the lack of standardization of the actual composition of a low residue diet.[2] The exact volume of residue produced by the digestion of various foods is challenging to calculate and reproduce consistently given microbiota and bowel function variability of the population.[3] Healthy gastrointestinal function and all foods can contribute to a certain degree of intestinal residue.[4] Incorrectly, a low residue diet is often interchangeably referred to as a low fiber diet. While fiber-containing foods contribute to fecal bulking, there are some exceptions. Milk, which is classically considered low in fiber, results in high colonic residue and fecal bulking.[5] For all these concerns, the American Dietetic Association has removed the low residue diet from the Nutrition Care Manual.[2]

A low residue diet is advocated for various clinical situations and illnesses. Until recently, a diet consisting of only liquids was recommended with bowel preparation before colonoscopies and colorectal surgeries. Numerous studies have shown either improved or equivalent bowel cleanliness in patients who consumed a low residue diet rather than a liquid diet with their bowel preparation. These same studies revealed enhanced overall patient satisfaction with a low residue diet and were less likely to cancel their procedure.[6][7][8][9][10][11] Both the American Society of Gastrointestinal Endoscopy and the European Society of Gastrointestinal Endoscopy now recommend the use of a low residue diet along with their bowel preparation.[12][13]

Clinicians often advise a low residue diet for patients during a flare-up of their inflammatory bowel disease; however, a recent systemic review did not find support for a therapeutic benefit in such patients.[14] For the same theoretical reason to reduce the risk of aggravating existing inflammation by decreasing colonic motility and allowing for “bowel rest,” a low residue diet is also advised for patients with infectious colitis or acute diverticulitis. This recommendation is based mostly on the clinical experience of healthcare providers as there is a paucity of high-quality evidence supporting any dietary change.[15] An additional potential role for a low residue diet was demonstrated in patients with irritable bowel syndrome in a randomized controlled trial.[3] In another randomized control trial, starting a low residue diet, rather than a liquid diet, on the first day after colorectal surgery was associated with better patient tolerance, quicker normalization of bowel function, and shorter length of hospitalization stay without increasing postoperative morbidity.[16]

In summary, a low residue diet is a restrictive diet that has both diagnostic and therapeutic roles. Regardless of the clinical indication, a low residue diet requires patient education to encourage compliance and to ensure that the patient is adequately following the diet as directed. Responsibilities of this education are deliverable by dietitians, nursing staff, and clinicians. Education is key to enhanced patient-centered care as it reinforces insight and understanding. It provides the patient with the complete opportunity to more likely obtain the desired outcomes of the diet.

When a clinician prescribes a patient a low residue diet, they should also be encouraged to maintain daily records of which foods they consume. Documentation will allow the healthcare team to support and ensure that patients are adherent to the dietary changes. The primary responsibility belonging to the patient will enable them to contribute to their care. This integrated approach is essential to deliver the best possible care and to improve patient outcomes.