title: A novel combined biomarker including plasma carotenoids, vitamin C, and ferric reducing antioxidant power is more strongly associated with fruit and vegetable intake than the individual components.
abstract: BACKGROUND
  Monitoring of fruit and vegetable (F&V) intake is fraught with difficulties. Available dietary assessment methods are associated with considerable error, and the use of biomarkers offers an attractive alternative. Few studies to date have examined the use of plasma biomarkers to monitor or predict the F&V intake of volunteers consuming a wide range of intakes from both habitual F&V and manipulated diets.
  
  
  OBJECTIVE
  This study tested the hypothesis that an integrated biomarker calculated from a combination of plasma vitamin C, cholesterol-adjusted carotenoid concentration and Ferric Reducing Antioxidant Power (FRAP) had more power to predict F&V intake than each individual biomarker.
  
  
  METHODS
  Data from a randomized controlled dietary intervention study [FLAVURS (Flavonoids University of Reading Study); n = 154] in which the test groups observed sequential increases of 2.3, 3.2, and 4.2 portions of F&Vs every 6 wk across an 18-wk period were used in this study.
  
  
  RESULTS
  An integrated plasma biomarker was devised that included plasma vitamin C, total cholesterol-adjusted carotenoids, and FRAP values, which better correlated with F&V intake (r = 0.47, P < 0.001) than the individual biomarkers (r = 0.33, P < 0.01; r = 0.37, P < 0.001; and r = 0.14, respectively; P = 0.099). Inclusion of urinary potassium concentration did not significantly improve the correlation. The integrated plasma biomarker predicted F&V intake more accurately than did plasma total cholesterol-adjusted carotenoid concentration, with the difference being significant at visit 2 (P < 0.001) and with a tendency to be significant at visit 1 (P = 0.07).
  
  
  CONCLUSIONS
  Either plasma total cholesterol-adjusted carotenoid concentration or the integrated biomarker could be used to distinguish between high- and moderate-F&V consumers. This trial was registered at www.controlled-trials.com as ISRCTN47748735.
authors.affiliation: Hugh Sinclair Unit of Human Nutrition and Institute of Cardiovascular and Metabolic Research, Department of Food and Nutritional Sciences, The University of Reading, Reading, Berks, UK.
authors.forename: Yannan
authors.initials: Y
authors.lastname: Jin
authors.affiliation: Hugh Sinclair Unit of Human Nutrition and Institute of Cardiovascular and Metabolic Research, Department of Food and Nutritional Sciences, The University of Reading, Reading, Berks, UK m.h.gordon@reading.ac.uk.
authors.forename: Michael H
authors.initials: MH
authors.lastname: Gordon
authors.affiliation: Hugh Sinclair Unit of Human Nutrition and Institute of Cardiovascular and Metabolic Research, Department of Food and Nutritional Sciences, The University of Reading, Reading, Berks, UK.
authors.forename: Dauren
authors.initials: D
authors.lastname: Alimbetov
authors.affiliation: Hugh Sinclair Unit of Human Nutrition and Institute of Cardiovascular and Metabolic Research, Department of Food and Nutritional Sciences, The University of Reading, Reading, Berks, UK.
authors.forename: Mary F-F
authors.initials: MF
authors.lastname: Chong
authors.affiliation: Hugh Sinclair Unit of Human Nutrition and Institute of Cardiovascular and Metabolic Research, Department of Food and Nutritional Sciences, The University of Reading, Reading, Berks, UK.
authors.forename: Trevor W
authors.initials: TW
authors.lastname: George
authors.affiliation: Hugh Sinclair Unit of Human Nutrition and Institute of Cardiovascular and Metabolic Research, Department of Food and Nutritional Sciences, The University of Reading, Reading, Berks, UK.
authors.forename: Jeremy P E
authors.initials: JP
authors.lastname: Spencer
authors.affiliation: Hugh Sinclair Unit of Human Nutrition and.
authors.forename: Orla B
authors.initials: OB
authors.lastname: Kennedy
authors.affiliation: Hugh Sinclair Unit of Human Nutrition and.
authors.forename: Kieran
authors.initials: K
authors.lastname: Tuohy
authors.affiliation: Hugh Sinclair Unit of Human Nutrition and.
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Minihane
authors.affiliation: Hugh Sinclair Unit of Human Nutrition and Institute of Cardiovascular and Metabolic Research, Department of Food and Nutritional Sciences, The University of Reading, Reading, Berks, UK.
authors.forename: Julie A
authors.initials: JA
authors.lastname: Lovegrove
mesh_terms: D000975:Antioxidants / Q000378:metabolism; D001205:Ascorbic Acid / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D002338:Carotenoids / Q000097:blood*; D005247:Feeding Behavior; D005260:Female; D005290:Ferric Compounds / Q000378:metabolism*; D005638:Fruit; D006801:Humans; D008297:Male; D008875:Middle Aged; D014675:Vegetables
chemical_list: D000975:Antioxidants; D015415:Biomarkers; D005290:Ferric Compounds; D002338:Carotenoids; D001205:Ascorbic Acid