title: Food groups and risk of chronic disease: a protocol for a systematic review and network meta-analysis of cohort studies.
abstract: There is a lack of systematic and comprehensive evaluations whether food intakes lower or increase risk of chronic diseases. In this network meta-analysis of prospective cohort studies, we aim to evaluate the effects of different foods on risk of chronic diseases.
  
  
  
  We will search PubMed and EMBASE. This will be supplemented by a hand search and author contacts. Citations, abstracts, and relevant papers will be screened for eligibility by two reviewers independently. Prospective cohort studies will be included if they meet the following criteria: (1) evaluate the association of single food or food groups with all-cause mortality, cardiovascular diseases (incidence and mortality), cancer (incidence and mortality) or risk of type 2 diabetes. The following food groups will be evaluated: whole grains, refined grains, vegetables, fruits, nuts, legumes, eggs, dairy products, fish, red meat, processed meat and sugar-sweetened beverages; (2) include participants ≥18 years of age; and (3) study population were free of outcome(s) of interest at the onset of the study. To assess study quality, we will extract the following characteristics: study size, duration of follow-up, dietary assessment method, assessment of outcome and adjustment factors. If the identified studies appear sufficiently similar within and across the different comparisons between pairs of food groups, we will estimate summary-relative effects using random effects network meta-analysis. Subgroup and meta-regression analyses will be performed stratified by different follow-up cut-points, geographical region and sex.
  
  
  
  This is a presentation of the study protocol only. Results and conclusions are pending completion of this study. Our systematic review will be of great value to national and international authorities for evidence-based nutritional recommendation/guidelines, regarding the implementation of food-based dietary guidelines for prevention of chronic diseases. Moreover, our results can be implemented to develop new diet quality indices/scores.
  
  
  
  PROSPERO CRD42016037069.
authors.affiliation: German Institute of Human Nutrition Potsdam-Rehbruecke (DIfE), Arthur-Scheunert-Allee 114-116, 14558, Nuthetal, Germany. lukas.schwingshackl@dife.de.
authors.forename: Lukas
authors.initials: L
authors.lastname: Schwingshackl
authors.affiliation: Department of Hygiene and Epidemiology University of Ioannina School of Medicine, Medical School Campus, University of Ioannina, Ioannina, 45110, Greece.
authors.forename: Anna
authors.initials: A
authors.lastname: Chaimani
authors.affiliation: German Nutrition Society, Godesberger Allee 18, 53175, Bonn, Germany.
authors.forename: Angela
authors.initials: A
authors.lastname: Bechthold
authors.affiliation: German Institute of Human Nutrition Potsdam-Rehbruecke (DIfE), Arthur-Scheunert-Allee 114-116, 14558, Nuthetal, Germany.
authors.forename: Khalid
authors.initials: K
authors.lastname: Iqbal
authors.affiliation: German Institute of Human Nutrition Potsdam-Rehbruecke (DIfE), Arthur-Scheunert-Allee 114-116, 14558, Nuthetal, Germany.|Department of Pediatric Gastroenterology and Metabolic Diseases, Poznan University of Medical Sciences, Szpitalna 27/33, 60-537, Poznan, Poland.
authors.forename: Marta
authors.initials: M
authors.lastname: Stelmach-Mardas
authors.affiliation: Department of Nutritional Sciences, University of Vienna, Althanstraße 14, UZA II, 1090, Vienna, Austria.
authors.forename: Georg
authors.initials: G
authors.lastname: Hoffmann
authors.affiliation: German Institute of Human Nutrition Potsdam-Rehbruecke (DIfE), Arthur-Scheunert-Allee 114-116, 14558, Nuthetal, Germany.
authors.forename: Carolina
authors.initials: C
authors.lastname: Schwedhelm
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Imperial College London, St. Mary's Campus, Norfolk Place, Paddington, London, W2 1PG, UK.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Schlesinger
authors.affiliation: German Institute of Human Nutrition Potsdam-Rehbruecke (DIfE), Arthur-Scheunert-Allee 114-116, 14558, Nuthetal, Germany.
authors.forename: Heiner
authors.initials: H
authors.lastname: Boeing
mesh_terms: D002318:Cardiovascular Diseases / Q000209:etiology / Q000401:mortality / Q000517:prevention & control; D002423:Cause of Death; D002908:Chronic Disease; D003924:Diabetes Mellitus, Type 2 / Q000209:etiology / Q000517:prevention & control; D004032:Diet; D005247:Feeding Behavior; D006801:Humans; D009369:Neoplasms / Q000209:etiology / Q000401:mortality / Q000517:prevention & control; D012107:Research Design; D000078202:Systematic Reviews as Topic; D015201:Meta-Analysis as Topic
keywords: Chronic disease; Diet; Food; Network meta-analysis