title: Glycemic index, glycemic load, carbohydrates, and type 2 diabetes: systematic review and dose-response meta-analysis of prospective studies.
abstract: OBJECTIVE
  Diets with high glycemic index (GI), with high glycemic load (GL), or high in all carbohydrates may predispose to higher blood glucose and insulin concentrations, glucose intolerance, and risk of type 2 diabetes. We aimed to conduct a systematic literature review and dose-response meta-analysis of evidence from prospective cohorts.
  
  
  METHODS
  We searched the Cochrane Library, MEDLINE, MEDLINE in-process, Embase, CAB Abstracts, ISI Web of Science, and BIOSIS for prospective studies of GI, GL, and total carbohydrates in relation to risk of type 2 diabetes up to 17 July 2012. Data were extracted from 24 publications on 21 cohort studies. Studies using different exposure categories were combined on the same scale using linear and nonlinear dose-response trends. Summary relative risks (RRs) were estimated using random-effects meta-analysis.
  
  
  RESULTS
  The summary RR was 1.08 per 5 GI units (95% CI 1.02-1.15; P = 0.01), 1.03 per 20 GL units (95% CI 1.00-1.05; P = 0.02), and 0.97 per 50 g/day of carbohydrate (95% CI 0.90-1.06; P = 0.5). Dose-response trends were linear for GI and GL but more complex for total carbohydrate intake. Heterogeneity was high for all exposures (I(2) >50%), partly accounted for by different covariate adjustment and length of follow-up.
  
  
  CONCLUSIONS
  Included studies were observational and should be interpreted cautiously. However, our findings are consistent with protective effects of low dietary GI and GL, quantifying the range of intakes associated with lower risk. Future research could focus on the type of sugars and other carbohydrates associated with greatest risk.
authors.affiliation: Corresponding author: Darren C. Greenwood, d.c.greenwood@leeds.ac.uk.
authors.forename: Darren C
authors.initials: DC
authors.lastname: Greenwood
authors.forename: Diane E
authors.initials: DE
authors.lastname: Threapleton
authors.forename: Charlotte E L
authors.initials: CE
authors.lastname: Evans
authors.forename: Christine L
authors.initials: CL
authors.lastname: Cleghorn
authors.forename: Camilla
authors.initials: C
authors.lastname: Nykjaer
authors.forename: Charlotte
authors.initials: C
authors.lastname: Woodhead
authors.forename: Victoria J
authors.initials: VJ
authors.lastname: Burley
mesh_terms: D001786:Blood Glucose / Q000378:metabolism*; D003924:Diabetes Mellitus, Type 2 / Q000097:blood*; D004040:Dietary Carbohydrates / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D018149:Glucose Intolerance / Q000097:blood / Q000209:etiology / Q000517:prevention & control; D038321:Glycemic Index; D006801:Humans; D006943:Hyperglycemia / Q000097:blood / Q000209:etiology / Q000517:prevention & control; D007328:Insulin / Q000097:blood; D011446:Prospective Studies; D012307:Risk Factors
chemical_list: D001786:Blood Glucose; D004040:Dietary Carbohydrates; D007328:Insulin