Discuss the primary factors that may be involved in IBS etiology. You must include in your discussion the possible roles of genetics, infection, and serotonin

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• Unknown cause
• Genetic predisposition: Genes that control serotonin receptors may make certain people more prone to IBS
• Gender: Affects more women than men
• Altered immune response stimulated by food sensitivity
• Patients may be able to identify certain foods that exacerbate symptoms
• Fermentable oligosaccharides, disaccharides, monosaccharides, and polyols or sugar alcohols (FODMAPs) may play a role in the development of IBS
• Altered microbial environment in the colon
- Abnormal colonic fermentation (partial digestion of food in the large intestine that may lead to excessive gas production as a by-product)
- Includes small intestine bacterial overgrowth
• Elevated inflammatory response to gastroenteritis (infection)
• Specific bacteria documented with gastroenteritis in the development of IBS:
• Salmonella
• Blastocystis hominis
• Campylobacter
• Parasites like Trichinella spiralis
• Heightened or abnormal communication between GI tract and muscle
• Increased sensitivity to the enteric system that changes motility
- Stimuli that most people would not react to cause symptoms of urgency, diarrhea, or constipation in IBS patients
- Stress and other psychological factors may exacerbate symptoms
• Commonly associated with celiac disease, Inflammatory bowel disease - not causes but these often co-exist with IBS.
• Abnormal release, transport, or recognition of serotonin
- 95% of serotonin is found in the GI tract, and serotonin can be either stimulatory or inhibitory to the GI tract, which is why people may have diarrhea, constipation, or a mix with IBS.
- Serotonin can either cause stimulation of acetylcholine, which causes muscle contraction, or it can cause release of nitric oxide, which relaxes smooth muscle in the GI tract.
- Altered serotonin levels are well documented in IBS patients.
• Documented reduced levels of serotonin in IBS-C patients
• Documented elevated levels of serotonin in IBS-D
• Although there is documentation, the exact role of serotonin in IBS is not understood

• Altered GI mucosal permeability may be caused by these previously discussed triggers and lead to inflammation and an altered perception of pain.

Nutritional Science

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