title: Combining vitamin C and carotenoid biomarkers better predicts fruit and vegetable intake than individual biomarkers in dietary intervention studies.
abstract: OBJECTIVE
  The aim of this study was to determine whether combining potential biomarkers of fruit and vegetables is better at predicting FV intake within FV intervention studies than single biomarkers.
  
  
  METHODS
  Data from a tightly controlled randomised FV intervention study (BIOFAV; all food provided and two meals/day on weekdays consumed under supervision) were used. A total of 30 participants were randomised to either 2, 5 or 8 portions FV/day for 4 weeks, and blood samples were collected at baseline and 4 weeks for plasma vitamin C and serum carotenoid analysis. The combined biomarker approach was also tested in three further FV intervention studies conducted by the same research team, with less strict dietary control (FV provided and no supervised meals).
  
  
  RESULTS
  The combined model containing all carotenoids and vitamin C was a better fit than either the vitamin C only (P < 0.001) model or the lutein only (P = 0.006) model in the BIOFAV study. The C-statistic was slightly lower in the lutein only model (0.85) and in the model based upon factor analysis (0.88), and much lower in the vitamin C model (0.68) compared with the full model (0.95). Results for the other studies were similar, although the differences between the models were less marked.
  
  
  CONCLUSIONS
  Although there was some variation between studies, which may relate to the level of dietary control or participant characteristics, a combined biomarker approach to assess overall FV consumption may more accurately predict FV intake within intervention studies than the use of a single biomarker. The generalisability of these findings to other populations and study designs remains to be tested. Clinical trial Registration Number NCT01591057 ( www.clinicaltrials.gov ).
authors.affiliation: Centre for Public Health, First Floor, Institute of Clinical Science B, Queen's University Belfast, Grosvenor Road, Belfast, BT12 6BJ, UK.
authors.forename: Alanna J
authors.initials: AJ
authors.lastname: McGrath
authors.affiliation: Centre for Public Health, First Floor, Institute of Clinical Science B, Queen's University Belfast, Grosvenor Road, Belfast, BT12 6BJ, UK.
authors.forename: Lesley L
authors.initials: LL
authors.lastname: Hamill
authors.affiliation: Centre for Public Health, First Floor, Institute of Clinical Science B, Queen's University Belfast, Grosvenor Road, Belfast, BT12 6BJ, UK.
authors.forename: Chris R
authors.initials: CR
authors.lastname: Cardwell
authors.affiliation: Centre for Public Health, First Floor, Institute of Clinical Science B, Queen's University Belfast, Grosvenor Road, Belfast, BT12 6BJ, UK.
authors.forename: Claire R
authors.initials: CR
authors.lastname: Draffin
authors.affiliation: Centre for Public Health, First Floor, Institute of Clinical Science B, Queen's University Belfast, Grosvenor Road, Belfast, BT12 6BJ, UK.
authors.forename: Charlotte E
authors.initials: CE
authors.lastname: Neville
authors.affiliation: Department of Psychology, Bournemouth University, Bournemouth, UK.
authors.forename: Katherine M
authors.initials: KM
authors.lastname: Appleton
authors.affiliation: Centre for Public Health, First Floor, Institute of Clinical Science B, Queen's University Belfast, Grosvenor Road, Belfast, BT12 6BJ, UK.
authors.forename: Jane
authors.initials: J
authors.lastname: McEneny
authors.affiliation: Centre for Public Health, First Floor, Institute of Clinical Science B, Queen's University Belfast, Grosvenor Road, Belfast, BT12 6BJ, UK.
authors.forename: Michelle C
authors.initials: MC
authors.lastname: McKinley
authors.affiliation: Centre for Public Health, First Floor, Institute of Clinical Science B, Queen's University Belfast, Grosvenor Road, Belfast, BT12 6BJ, UK.
authors.forename: Ian S
authors.initials: IS
authors.lastname: Young
authors.affiliation: Centre for Public Health, First Floor, Institute of Clinical Science B, Queen's University Belfast, Grosvenor Road, Belfast, BT12 6BJ, UK. j.woodside@qub.ac.uk.
authors.forename: Jayne V
authors.initials: JV
authors.lastname: Woodside
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001205:Ascorbic Acid / Q000008:administration & dosage / Q000097:blood*; D015415:Biomarkers / Q000097:blood*; D001794:Blood Pressure; D015992:Body Mass Index; D002338:Carotenoids / Q000008:administration & dosage / Q000097:blood*; D004032:Diet; D005260:Female; D005638:Fruit; D006801:Humans; D014975:Lutein / Q000097:blood; D008297:Male; D008875:Middle Aged; D015596:Nutrition Assessment; D012959:Socioeconomic Factors; D014675:Vegetables; D055105:Waist Circumference; D055815:Young Adult
chemical_list: D015415:Biomarkers; D002338:Carotenoids; D001205:Ascorbic Acid; D014975:Lutein
keywords: Biomarkers; Dietary intake; Fruit; Methodology; Vegetables