The Study For The Role Of Dietary Factors In The Etiology And Management Of Irritable Bowel Syndrome

Background Because of the heavy impact of chronic conditions of healthy status and health care expenditures, management of irritable bowel syndrome (IBS) is one of the major challenges in recent years. Patients often report the precipitation of symptoms on special foods ingestion and/or special eating behaviors. Through by now the role of dietary constituents in IBS has not been extensively studied, there is growing interest in effective dietary manipulation and prebiotics, to provide patients prolonged symptom-free time and to facilitate remission in exacerbation.Aims (1) To identify among patients with IBS:①the potential role of dietary components in IBS symptoms causations and exacerbations;②the empirical strategies used by patients to manage symptoms;③the long-term impacts of dietary components on nutritional status of chronic illness.(2) To study among animal models with IBS:the effects and the possible mechanisms of a prebiotic on symptoms of IBS.Materials and Methods The study was performed in two parts.(1) Fifty eight of IBS outpatients who met ROME Ⅲ criteria were enrolled from February,2011to May,2011. The questionnaire on IBS symptoms and dietary factors was recorded to retrospectively collect possible dietary constituents once caused exacerbations and adaptive strategies once promoted remissions; and Mini Nutritional Assessment was performed to evaluate nutritional status.(2) IBS animal model using water avoidance stress(WAS group) was Established and the efficiency was evaluated via body weight, fecal pellets output, and abdominal withdrawal reflex scores; IBS rats were randomized to receive prebiotic isomalto-oligosaccharides(WAS+IMO group) or water(WAS+water group) for two weeks and then the treatment effects were evaluated via body weight, serum albumin level, fecal pellets output, gastrointestinal transit rate, abdominal withdrawal reflex scores, ultra-structure of intestinal epitheliums by scanning electron microscopy, isolation and culture of fresh fecal flora and serum cytokines level (IL-10,IL-12,TNF-α) measurement by ELISA.Results In the clinical study, we found:①most IBS patients had a variety of dietary triggers, while cold foods(66.67%), spicy foods (61.11%), raw foods (53.70%), greasy foods (53.70%), dairy products (excluding yogurt)(37.04%) were the top five incentives; 65.31%IBS patients selected exclusion diet to relieve symptoms; most of patients weeded out spicy foods(79.50%), followed by cold foods(77.30%), raw foods(65.90%) and greasy foods(56.80%); part of patients chose hot water drinking/hot water compress(16.33%) or hot porridge (12.24%) as their managing strategies;③the number of food incentives had a positive correlation with BMI(P=0.016) and MNA score(P=0.038).These results indicate that dietary factors have close relationship with the onset and relief of IBS symptoms.Results from the animal model study include:①the WAS group had slower body weight gain than the control group(271±26g, n=16vs294±13g, n=8,P=0.007);②in the stress period, the WAS group had more fecal pellets per hour than the control group(12.19±2.713pellets vs1.13±1.885pellets, P=0.000), with a higher percentage of deformed fecal pellets(22.19±18.15%vs.0.00±0.00%, P=0.000);③compared with the control group, the WAS group got higher abdominal withdrawal reflex (AWR)scores at the pressure level20mmHg(1.91±0.51,n=16vs1.11±0.29, n=6, P=0.002) and lower pain threshold(31.88±5.69mmHg vs48.00±8.39mmHg, P=0.000);④after isomalto-oligo-saccharides therapy, the WAS+IMO group had lower AWR scores than the WAS+water group(2.52±0.88, n=7vs3.52±0.36, n=5, P=0.020) at the same colorectal distention pressure level40mmHg; also, the pain threshold of the WAS+IMO group had not significant difference with the control group(39.86±11.75mmHg, n=7vs51.00±2.76mmHg, n=6, P=0.133);⑤the gastrointestinal transit rate in the WAS+IMO group increased significantly comparing with the control group(66.93±4.85%vs58.87±5.27%, P=0.042);⑥in the observation of ultrastructure of intestinal epithelium, the WAS+water group showed numerous secretary granules on the gland pits, goblet cell shrinkage, E. coli adherence on goblet cells, enlargement of the space between epithelial, partial loss of microvilli, and uneven distribution of microvilli; while the WAS+IMO group showed some recovery from above situation;⑦the WAS+IMO group had lower count of bacteroides than WAS+water group(4.25±0.24vs4.57±0.28, P=0.035);⑧there was no significant difference among the three groups in serum cytokines level(IL-10, IL-12,TNF-a).Conclusions (1) Cold foods, spicy foods, raw foods, greasy foods and dairy products are the most common dietary trigger; in the contrast, exclusion diet has good response in IBS patients. Hot water drinking/compress or hot porridge can also works as an adaptive strategy. The number of food incentives may relates to the severity, but does not deteriorate nutritional status.(2)As an appropriate IBS animal model, water avoidance stress can slow rats weight gain, alternate gastrointestinal motility, lead to lasting and stable visceral hypersensitivity. Isomalto-oligosaccharide intervention can significantly improve visceral hypersensitivity in WAS rats, ameliorate the gastrointestinal transportation, and restore the ultrastructure damage. The efficacy may come from the inhibition of potentially pathogenic microorganisms.