title: Dietary intake and risk of developing inflammatory bowel disease: a systematic review of the literature.
abstract: OBJECTIVE
  The incidence of inflammatory bowel disease (IBD) is increasing. Dietary factors such as the spread of the "Western" diet, high in fat and protein but low in fruits and vegetables, may be associated with the increase. Although many studies have evaluated the association between diet and IBD risk, there has been no systematic review.
  
  
  METHODS
  We performed a systematic review using guideline-recommended methodology to evaluate the association between pre-illness intake of nutrients (fats, carbohydrates, protein) and food groups (fruits, vegetables, meats) and the risk of subsequent IBD diagnosis. Eligible studies were identified via structured keyword searches in PubMed and Google Scholar and manual searches.
  
  
  RESULTS
  Nineteen studies were included, encompassing 2,609 IBD patients (1,269 Crohn's disease (CD) and 1,340 ulcerative colitis (UC) patients) and over 4,000 controls. Studies reported a positive association between high intake of saturated fats, monounsaturated fatty acids, total polyunsaturated fatty acids (PUFAs), total omega-3 fatty acids, omega-6 fatty acids, mono- and disaccharides, and meat and increased subsequent CD risk. Studies reported a negative association between dietary fiber and fruits and subsequent CD risk. High intakes of total fats, total PUFAs, omega-6 fatty acids, and meat were associated with an increased risk of UC. High vegetable intake was associated with a decreased risk of UC.
  
  
  CONCLUSIONS
  High dietary intakes of total fats, PUFAs, omega-6 fatty acids, and meat were associated with an increased risk of CD and UC. High fiber and fruit intakes were associated with decreased CD risk, and high vegetable intake was associated with decreased UC risk.
authors.affiliation: Section of Gastroenterology, Baylor College of Medicine, Houston, TX, USA. jkhou@bcm.tmc.edu
authors.forename: Jason K
authors.initials: JK
authors.lastname: Hou
authors.forename: Bincy
authors.initials: B
authors.lastname: Abraham
authors.forename: Hashem
authors.initials: H
authors.lastname: El-Serag
mesh_terms: D003093:Colitis, Ulcerative / Q000209:etiology; D003424:Crohn Disease / Q000209:etiology; D004032:Diet / Q000009:adverse effects*; D004040:Dietary Carbohydrates / Q000008:administration & dosage / Q000009:adverse effects; D004041:Dietary Fats / Q000009:adverse effects; D004043:Dietary Fiber / Q000008:administration & dosage; D004044:Dietary Proteins; D043371:Fatty Acids, Omega-6 / Q000008:administration & dosage; D005231:Fatty Acids, Unsaturated / Q000008:administration & dosage; D005638:Fruit; D006801:Humans; D015212:Inflammatory Bowel Diseases / Q000209:etiology* / Q000517:prevention & control; D008460:Meat / Q000009:adverse effects; D018570:Risk Assessment; D014675:Vegetables
chemical_list: D004040:Dietary Carbohydrates; D004041:Dietary Fats; D004043:Dietary Fiber; D004044:Dietary Proteins; D043371:Fatty Acids, Omega-6; D005231:Fatty Acids, Unsaturated