title: Polyphenol-rich diets improve glucose metabolism in people at high cardiometabolic risk: a controlled randomised intervention trial.
abstract: OBJECTIVE
  Dietary polyphenols and long chain n-3 polyunsaturated fatty acids (LCn3) are associated with lower cardiovascular risk. This may relate to their influence on glucose metabolism and diabetes risk. We evaluated the effects of diets naturally rich in polyphenols and/or LCn3 of marine origin on glucose metabolism in people at high cardiometabolic risk.
  
  
  METHODS
  According to a 2 × 2 factorial design, individuals with high waist circumference and at least one more component of the metabolic syndrome were recruited at the obesity outpatient clinic. Eighty-six participants were randomly assigned by MINIM software to an isoenergetic diet: (1) control, low in LCn3 and polyphenol (analysed n = 20); (2) rich in LCn3 (n = 19); (3) rich in polyphenols (n = 19); or (4) rich in LCn3 and polyphenols (n = 19). The assigned diets were known for the participants and blinded for people doing measurements. Before and after the 8 week intervention, participants underwent a 3 h OGTT and a test meal with a similar composition as the assigned diet for the evaluation of plasma glucose, insulin and glucagon-like peptide 1 (GLP-1) concentrations, and indices of insulin sensitivity and beta cell function.
  
  
  RESULTS
  During OGTT, polyphenols significantly reduced plasma glucose total AUC (p = 0.038) and increased early insulin secretion (p = 0.048), while LCn3 significantly reduced beta cell function (p = 0.031) (two-factor ANOVA). Moreover, polyphenols improved post-challenge oral glucose insulin sensitivity (OGIS; p = 0.05 vs control diet by post hoc ANOVA). At test meal, LCn3 significantly reduced GLP-1 total postprandial AUC (p < 0.001; two-factor ANOVA).
  
  
  CONCLUSIONS
  Diets naturally rich in polyphenols reduce blood glucose response, likely by increasing early insulin secretion and insulin sensitivity. These effects may favourably influence diabetes and cardiovascular risk. The implications of the decrease in insulin secretion and postprandial GLP-1 observed with diets rich in marine LCn3 need further clarification.
  
  
  BACKGROUND
  ClinicalTrials.gov NCT01154478.
  
  
  BACKGROUND
  The trial was funded by European Community's Seventh Framework Programme FP7/2009-2012 under grant agreement FP7-KBBE-222639, Etherpaths Project and 'Ministero Istruzione Università e Ricerca' PRIN 2010-2011 - 2010JCWWKM.
authors.affiliation: Department of Clinical Medicine and Surgery, Federico II University, Via Pansini, 5, 80131, Naples, Italy.
authors.forename: Lutgarda
authors.initials: L
authors.lastname: Bozzetto
authors.forename: Giovanni
authors.initials: G
authors.lastname: Annuzzi
authors.forename: Giovanni
authors.initials: G
authors.lastname: Pacini
authors.forename: Giuseppina
authors.initials: G
authors.lastname: Costabile
authors.forename: Claudia
authors.initials: C
authors.lastname: Vetrani
authors.forename: Marilena
authors.initials: M
authors.lastname: Vitale
authors.forename: Ettore
authors.initials: E
authors.lastname: Griffo
authors.forename: Angela
authors.initials: A
authors.lastname: Giacco
authors.forename: Claudia
authors.initials: C
authors.lastname: De Natale
authors.forename: Sara
authors.initials: S
authors.lastname: Cocozza
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Della Pepa
authors.forename: Andrea
authors.initials: A
authors.lastname: Tura
authors.forename: Gabriele
authors.initials: G
authors.lastname: Riccardi
authors.forename: Angela A
authors.initials: AA
authors.lastname: Rivellese
mesh_terms: D000328:Adult; D000368:Aged; D001786:Blood Glucose / Q000378:metabolism; D002318:Cardiovascular Diseases / Q000178:diet therapy* / Q000517:prevention & control*; D004032:Diet; D015525:Fatty Acids, Omega-3 / Q000494:pharmacology; D005260:Female; D052216:Glucagon-Like Peptide 1 / Q000097:blood; D005947:Glucose / Q000378:metabolism*; D005951:Glucose Tolerance Test; D006801:Humans; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance; D050417:Insulin-Secreting Cells / Q000378:metabolism; D008297:Male; D008659:Metabolic Diseases / Q000178:diet therapy* / Q000517:prevention & control*; D008875:Middle Aged; D009765:Obesity / Q000178:diet therapy; D010349:Patient Compliance; D059808:Polyphenols / Q000494:pharmacology*; D055105:Waist Circumference
chemical_list: D001786:Blood Glucose; D015525:Fatty Acids, Omega-3; D007328:Insulin; D059808:Polyphenols; D052216:Glucagon-Like Peptide 1; D005947:Glucose