Introduction: Inflammatory bowel disease (IBD) refers to two chronic diseases that cause intestinal inflammation, ulcerative colitis (UC) and Crohn's disease (CD). The conventional treatment is not effective; therefore, alternative therapies may be effective specially in UC patients. Fatty acid (FA) may have a beneficial effect on some UC patients. The increasing incidence and prevalence of UC and ineffective treatments in some patients, allows search coadjuvant therapies. Objective: Quantification of differences between patients with and without FA. Methods: In two groups of patients with UC is administered FA and placebo. We will measure the changes clinical, endoscopic and histological in both groups, before and after treatment.

Inclusion Criteria:

• Patients with a histopathologically confirmed diagnosis of UC.
• With mild and moderate disease.
• Patients treated with only doses of 5-aminosalicylates (5-ASA)
• BMI, 18 to 34.9 kg/m2
• Born in Mexico the last two generations
• Each patient will be asked to sign and date the consent form, to indicate that you agree to participate.

Exclusion Criteria:

• Patient with associated diseases such as diabetes mellitus, hypertension, dyslipidemia, atherosclerosis and malabsorption syndrome.
• With autoimmune diseases (lupus, HIV, cancer and hepatitis), colitis (infectious, post-radiation, post-drug, indeterminate) and Crohn's Disease.
• If the patient use drugs that inhibit fat absorption.
• Patients after partial or total resection of stomach or small intestine.
• Steroid users.
• Patients in remission histology, clinical and endoscopic.
• Patients treated with FAn-3,6 or 9.