This is a GWAS that aims to identify possible single nucleotide polymorphisms (SNPs) that are associated with the response in a combined dietary pattern low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols and Meditteranean diet (MED-LFD) in a small group of patients with Irritable Bowel Syndrome (IBS).
Fulfillment of the Rome IV criteria for IBS
Provision of written informed consent.
Commitment of availability throughout the study period.
IBS-SSS > 175
Any concomitant disease requiring specialized nutrition (e.g. renal failure, diabetes, celiac disease, cerebrovascular disease of the central nervous system, major surgical cavity).
Pregnancy.
Breastfeeding.
Patients 18-65 years with IBS (fullfiling ROME IV criteria) who have IBS-SSS\>175. People with any concomitant disease requiring specialized nutrition, pregnant or lactating women will be excluded.
Case-only
Prospective
Med-LFD intervention
Other interventionIn the beginning of the intervention, blood and stool samples will be collected. All participants of the group at phase 1 (elimination phase), will initially follow the Med- LFD (2-6 weeks). At phase 2 (reintroduction phase), patients will gradually reintroduce foods rich in FODMAPs (6-8 weeks) and test their tolerance. At phase 3 (maintenance phase), following the reintroduction of foods rich in FODMAPs, patients will follow an individualized diet based on their personal tolerance (a combination of high and low FODMAPs). In the end of intervention, stool samples will be collected again.
Find single nucleotide polymorphisms (SNPs) that associate with the diet respone
Blood samples will be collected for DNA extraction. Genotyping be based on Next Generation Sequencing (NGS). Quality control (QC) filtering will be applied at individual-and variant-level using specialized software.
Change of symptoms severity pre and post intervention using a specialized questionnaire.
IBS- SSS contains 5 specific questions with instructions on how to score them. Each of the five questions (pain severity, pain frequency, abdominal distension severity, bowel movement satisfaction, quality of life) ranges from 0 to a maximum score of 100 using a visual analog scale (VAS) with total scores ranging from 0 to 500, with higher scores indicating more severe symptoms. Subjects can be categorized as having mild (75-175), moderate (175-300), or severe (\>300) IBS. A decrease of 50 points is associated with a clinically meaningful improvement.
Evaluation of the effect of interventions on gut microbiota composition between groups.
Fecal samples will be collected from each participant and stored at -80°C.
Assessment of general quality of life pre and post intervention between groups
12-Item Short Form Survey (SF-12) is a 12-item questionnaire used to assess generic health outcomes from the patient's perspective, covering the eight domains of health outcomes: physical functioning, role-physical, bodily pain, general health, vitality, social functioning, role-emotional \& mental health. The items are weighted and summed to provide physical and mental health scores (PCS and MCS). The two composite scores are computed using the scores on the questions that range from 0 to 100, with higher score indicating better health.
Assessment of symptoms burden in general pre and post intervention.
The GSRS questionnaire was originally developed for dyspeptic patients but was later validated in patients with IBS. The GSRS is a 15-item questionnaire designed to assess common gastrointestinal symptoms. The questionnaire has five subscales, reflux, diarrhea, constipation, indigestion, and abdominal pain, with subscale scores ranging from 1 (no discomfort) to 7 (severe discomfort). Higher scores represent higher symptom burden.
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