Effect of Tryptophan Restriction in the Therapy of Irritable Bowel Syndrome: a Systematic Review

Ben Wang,1,2 Peilin Cheng,2 Bingjie Jin,2 Ying Jiang,2 Qingcai Wang,1 Hongwei Xu2 1Department of Gastroenterology, The Affiliated Taian City Central Hospital of Qingdao University, Taian, People’s Republic of China; 2Department of Gastroenterology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, People’s Republic of ChinaCorrespondence: Hongwei Xu, Department of Gastroenterology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, People’s Republic of China, Email xuhongwei@sdfmu.edu.cnBackground & Aims: The metabolic pathways of tryptophan (TRP) have been implicated in the pathophysiology of irritable bowel syndrome (IBS), positing that the strategic modulation of TRP consumption may exert regulatory effects on serotonin levels, consequently altering the clinical manifestation of IBS. This systematic review was meticulously orchestrated to evaluate the effect of TRP restriction on IBS.Methods: A comprehensive search of the MEDLINE/PubMed, Cochrane Library, and Embase databases was conducted. Controlled trials that compared the efficacy of TRP restriction in IBS patients were scrutinized. The primary outcomes were gastrointestinal symptoms, quality of life, and pain, whereas the secondary outcomes included anxiety, mood, and safety. The risk of bias was meticulously assessed according to the guidelines recommended by the Cochrane Collaboration.Results: A total of five trials, enrolling 135 participants, were incorporated into the qualitative synthesis. Low-TRP intake attenuated gastrointestinal discomfort and enhanced psychological well-being in IBS patients, while the effects of acute TRP depletion were controversial. Safety data from one randomized controlled trial reported no occurrence of adverse events.Conclusion: This systematic review suggests that moderating, rather than depleting, TRP intake may potentially be a feasible and safe adjunctive treatment for patients with IBS. Future research incorporating a high-quality study design and consensus on clinical outcome measurements for IBS is warranted.Keywords: irritable bowel syndrome, reduced tryptophan diet, acute tryptophan depletion, systematic review