{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,24]],"date-time":"2026-08-24T23:01:33Z","timestamp":1787612493942,"version":"build-2736575974"},"reference-count":36,"publisher":"MDPI AG","issue":"23","license":[{"start":{"date-parts":[[2022,12,5]],"date-time":"2022-12-05T00:00:00Z","timestamp":1670198400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Medical University of Lodz","award":["NN-503-006-05\/18"],"award-info":[{"award-number":["NN-503-006-05\/18"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJMS"],"abstract":"<jats:p>(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 \u00b1 38.1 vs. 142.3 \u00b1 36.4 ng\/mL; p &lt; 0.001) but a similar level of melatonin (8.6 \u00b1 1.1 vs. 9.4 \u00b1 3.0 pg\/mL; p &gt; 0.05). The urinary excretion of 5-HIAA was also higher in patients with IBS-D patients (7.7 \u00b1 1.5 vs. 6.0 \u00b1 1.7 mg\/24 h; p &lt; 0.001). After nutritional treatment, both the serum serotonin level and the urinary 5-HIAA excretion significantly decreased (p &lt; 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.<\/jats:p>","DOI":"10.3390\/ijms232315314","type":"journal-article","created":{"date-parts":[[2022,12,5]],"date-time":"2022-12-05T02:13:12Z","timestamp":1670206392000},"page":"15314","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":18,"title":["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"],"prefix":"10.3390","volume":"23","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-1620-4775","authenticated-orcid":false,"given":"Cezary","family":"Chojnacki","sequence":"first","affiliation":[{"name":"Department of Clinical Nutrition and Gastroenterological Diagnostics, Medical University of Lodz, 90-647 Lodz, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Marta","family":"Medrek-Socha","sequence":"additional","affiliation":[{"name":"Department of Clinical Nutrition and Gastroenterological Diagnostics, Medical University of Lodz, 90-647 Lodz, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Aleksandra","family":"Blonska","sequence":"additional","affiliation":[{"name":"Department of Clinical Nutrition and Gastroenterological Diagnostics, Medical University of Lodz, 90-647 Lodz, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1654-8957","authenticated-orcid":false,"given":"Radoslaw","family":"Zajdel","sequence":"additional","affiliation":[{"name":"Department of Computer Science in Economics, University of Lodz, 90-237 Lodz, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8766-7868","authenticated-orcid":false,"given":"Jan","family":"Chojnacki","sequence":"additional","affiliation":[{"name":"Department of Clinical Nutrition and Gastroenterological Diagnostics, Medical University of Lodz, 90-647 Lodz, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2300-7339","authenticated-orcid":false,"given":"Tomasz","family":"Poplawski","sequence":"additional","affiliation":[{"name":"Department of Pharmaceutical Microbiology and Biochemistry, Medical University of Lodz, 90-136 Lodz, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2022,12,5]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Bassotti, G. 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