title: Dose-response effect of fruit and vegetables on insulin resistance in people at high risk of cardiovascular disease: a randomized controlled trial.
abstract: OBJECTIVE
  The purpose of this randomized controlled trial was to investigate the dose-response effect of fruit and vegetable (F&V) intake on insulin resistance (IR) in people who are overweight and at high risk of cardiovascular disease (CVD).
  
  
  METHODS
  A total of 105 participants (mean age 56 years) followed a 4-week washout diet (one to two portions of F&Vs per day). Ninety-two participants completed the washout and were randomized to receive one to two, four, or seven portions of F&Vs per day for 12 weeks. IR was assessed at the start and end of this 12-week period by the two-step euglycemic-hyperinsulinemic clamp. Compliance was monitored using a combination of 4-day food diaries and plasma biomarkers of F&V intake.
  
  
  RESULTS
  A total of 89 participants completed the study. Participants attained self-reported F&V intakes of 1.8, 3.8, and 7.0 portions per day (P < 0.001) per group. There was a significant linear increase in serum lutein status across the groups, indicating good compliance (P < 0.001), and body weight was maintained (P = 0.77). No significant difference was found between groups in terms of a change in measures of whole-body, peripheral, or hepatic IR or adiponectin multimers.
  
  
  CONCLUSIONS
  Increased consumption of F&Vs, as advocated in public-health advice, has no effect on IR in overweight individuals who are at high risk of CVD when body weight is maintained. Recent evidence from systematic reviews indicates that particular classes or types of F&Vs may have particular antidiabetic properties; hence, it is possible that benefits may only be observed in response to a more specific fruit or vegetable intervention.
authors.affiliation: Corresponding author: Michelle C. McKinley, m.mckinley@qub.ac.uk.
authors.forename: Ian R
authors.initials: IR
authors.lastname: Wallace
authors.forename: Claire T
authors.initials: CT
authors.lastname: McEvoy
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Hunter
authors.forename: Lesley L
authors.initials: LL
authors.lastname: Hamill
authors.forename: Cieran N
authors.initials: CN
authors.lastname: Ennis
authors.forename: Patrick M
authors.initials: PM
authors.lastname: Bell
authors.forename: Chris C
authors.initials: CC
authors.lastname: Patterson
authors.forename: Jayne V
authors.initials: JV
authors.lastname: Woodside
authors.forename: Ian S
authors.initials: IS
authors.lastname: Young
authors.forename: Michelle C
authors.initials: MC
authors.lastname: McKinley
mesh_terms: D015415:Biomarkers / Q000097:blood; D001835:Body Weight; D002318:Cardiovascular Diseases / Q000209:etiology / Q000517:prevention & control*; D015930:Diet Records; D005247:Feeding Behavior; D005260:Female; D005500:Follow-Up Studies; D005638:Fruit; D006801:Humans; D007333:Insulin Resistance; D008297:Male; D008875:Middle Aged; D050177:Overweight / Q000150:complications / Q000178:diet therapy*; D012189:Retrospective Studies; D012307:Risk Factors; D014675:Vegetables
chemical_list: D015415:Biomarkers