Gastrointestinal disorders represents 20-50% of referrals to the gastroenterologist; being the most affected womens, youths and older adults. Among these alterations are the Irritable Bowel Syndrome (IBS) and Ulcerative Colitis (UC), which affects the gut causing impaired motility. The pharmacological and nutritional treatment are modified according to the symptomatology and activity of each patients. Currently the implementation of low FODMAP diets for 6 to 8 weeks in patients whith IBS improves symptoms such as bloating, flatulence and abdominal pain. However due to the number of restricted foods a long term attachment could limited the nutritional content, consequently affecting the nutritional status, gut microbiota an quality of life. A low FODMAP diet are useful to improve gastrointestinal symptoms in patients with UC and causes changes in nutritional status.

Irritable Bowel Syndrome (IBS) and Ulcerative Colitis (UC) affect principally the gut, causing symptoms that alter intestinal motility, with a multifactorial etiology. The pharmacological and nutritional treatment varies according to the symptoms and activity of each patient. The most commonly used are the standard diet (SD), which excludes foods known as irritants or inflammatory. On the other hand, are the low fodmap diet (LFD) (fermentable oligosaccharides. disaccharides, monosaccharides and polyols), these highly fermentable carbohydrates can pass unabsorbed to the colon and induce the gas production due to the fermentation of gut microbiota and cause symptoms such as: bloating, flatulence, abdominal pain and altered bowel habit. It consists in two stages: first the restriction of all foods that contain fodmaps and second the re exposure in which indicate the introduction of each food restricted before to evaluate the tolerance, for 6 to 8 weeks. Some studies show that the low fodmap diet improve the symptoms in both groups, however because of the restriction and the limited content of foods, they have had risk to present nutritional deficiencies. The aim of the present is to evaluate the effect of a low fodmap diet for 10 weeks on gastrointestinal symptoms, nutritional status and microbiota in patients with IBS and UC.

Methods: a controlled, blinded clinical trial will be conducted in patients who assist to medical monitoring in gastroenterology service with diagnosis of IBS or UC. The sample size was determined with a 0.5 effect size, an alpha error 0.05 and power of 80%, which determined 64 patients for each group (total: 128). After singing the informed consent, will be determined their total energy expenditure (TEE) and consecutively will be assigned an ID previously randomized to SD (<16 g of fodmaps) or LFD (<10 g of fodmaps), with a distribution of 55% carbohydrates, 20% proteins and 25% lipids. During the 10 weeks will be three follow-ups, first the basal, intermediate (week 5) and final (10 weeks after), will be performed body composition (RJL Quantum III), anthropometry (waist, hip, arm and chest circumference), gastrointestinal symptoms (ROMA III and Mayo Scale), quality of life (WHOQL-BREF), food frequency and 24-hour reminder and blood chemistry (anemia, hypoalbuminemia, vitamin D, calcium, potassium, c reactive protein, VSG, etc), all of them basal and final.

Inclusion Criteria:

• Irritable Bowel Syndrome confirmed by Rome criteria III
• Ulcerative Colitis confirmed by Mayo Scale
• Informed Consent signed
• BMI between 18.5 and 29.9 kg/m2
• Males and females
• Age between 18-59 years
• Mexican patients

Exclusion Criteria:

• Chron´s disease diagnosed
• Treatment whith antibiotis during the last two weeks
• Bowel resection
• Short bowel syndrome
• Treatment wihth probiotics or enzimes (A-galactosidase)
• Pregnancy
• Nutritional deficiencies or anemia
• Patients whith diet supplements

The patient doesn´t know the type of diet (standard or low FODMAP)