A Reduced Tryptophan Diet in Patients with Diarrhoea-Predominant Irritable Bowel Syndrome Improves Their Abdominal Symptoms and Their Quality of Life through Reduction of Serotonin Levels and Its Urinary Metabolites

Abstract

(1). An essential component of any treatment for patients with irritable bowel syndrome (IBS) is an adequate diet. Currently, a low FODMAP diet is recommended as a first-line therapy, but it does not relieve abdominal discomfort in all patients, and alternative nutritional treatment is required. The purpose of this study was to evaluate the effect of a tryptophan-lowering diet (TRP) on abdominal and mental symptoms in patients with irritable bowel syndrome with predominant diarrhea (IBS-D). (2). The study included 40 patients with IBS-D, and 40 healthy subjects served as a baseline for IBS-D patients, after excluding comorbidities. The TRP intake was calculated using the nutritional calculator. The severity of abdominal symptoms was assessed using the gastrointestinal symptom rating scale (GSRS-IBS). Mental state was assessed using the Hamilton anxiety rating scale (HAM-A), the Hamilton depression rating scale (HAM-D), and the insomnia severity index (ISI). The serum levels of serotonin and melatonin and the urinary excretion of their metabolites 5-hydroxyindoleacetic acid (5-HIAA) and 6-sulfatoxymelatonin (aMT6) were determined by the ELISA method. The severity of symptoms and laboratory data were analyzed before and after a 12 week diet with tryptophan restricted to a daily dose 10 mg per kilogram body weight. (3). Compared to the control group, patients with IBS-D had a higher serum level of serotonin (198.2 ± 38.1 vs. 142.3 ± 36.4 ng/mL; p < 0.001) but a similar level of melatonin (8.6 ± 1.1 vs. 9.4 ± 3.0 pg/mL; p > 0.05). The urinary excretion of 5-HIAA was also higher in patients with IBS-D patients (7.7 ± 1.5 vs. 6.0 ± 1.7 mg/24 h; p < 0.001). After nutritional treatment, both the serum serotonin level and the urinary 5-HIAA excretion significantly decreased (p < 0.001). The severity of the abdominal symptoms and anxiety also decreased, while the HAM-D score and the ISI score remained unchanged (4). Lowering the dietary intake of tryptophan may reduce abdominal complaints and does not alter the mental state of IBS-D patients.

Different regulatory mechanisms of Na+/ glucose transport in mouse ileum and jejunum

“…Rather, we revealed that the 5-HT4R/cAMP/PKA pathway negatively regulated ileal glucose absorption, consistent with previous reports that cAMP/PKA inhibited NHE3 to regulate SGLT1 activity in mouse ileum [37,25,24]. High levels of 5-HT in the gastrointestinal tract are associated with diarrhea-related celiac disease, irritable bowel syndrome, and carcinoid syndrome [7,13]. 5-HT has a propulsive effect on the gastrointestinal tract.…”

Reduced Intake of Dietary Tryptophan Improves Beneficial Action of Budesonide in Patients with Lymphocytic Colitis and Mood Disorders

“…In our previous study in patients with LC, we found an increase in the number of enterochromaffin cells (ECs) and in the activity of tryptophan hydroxylase (TPH-1) in colonic mucosa, as well as an increase in serum serotonin levels [ 25 ]. In our next study, we found improvement in abdominal and mental symptoms after reducing TRP intake in patients with diarrhea-predominant irritable bowel syndrome, as well as beneficial changes in metabolism [ 26 ]. The above results inspired further research on the role of this amino acid in the pathogenesis of LC.…”