title: A method comparison of a food frequency questionnaire to measure folate, choline, betaine, vitamin C and carotenoids with 24-h dietary recalls in women of reproductive age.
abstract: OBJECTIVE
  The objective of this study was to conduct a method comparison of a modified food frequency questionnaire (FFQ), designed to estimate usual dietary intake of selected micronutrients and antioxidants including folate, choline, betaine, vitamin C and carotenoids (α-carotene, β-carotene, lutein, lycopene and β-cryptoxanthin) with 24-h dietary recalls (24-HR) in women of reproductive age.
  
  
  METHODS
  Sixty-four British women of reproductive age (18-40 years) were recruited in Oxford, UK and provided complete dietary data for analysis.
  
  
  METHODS
  We compared micronutrient estimates from the FFQ against estimates derived from three multiple-pass, 24-HR interviews, by evaluating Pearson's correlation coefficients and Bland-Altman plots.
  
  
  RESULTS
  Median intakes of most nutrients were higher when measured by FFQ compared with 24-HR. Strong correlation coefficients were observed for folate (r=0.80) and choline (r=0.68), whereas moderate correlation coefficients were observed for vitamin C (0.50) and lycopene (0.43). Weak correlation coefficients were observed for betaine (0.39) and other carotenoids (r=0.26-0.38). Bland-Altman plots indicated that there was a large amount of variability in the FFQ estimates of nutrient intakes compared to those using 24-HR, particularly for carotenoids.
  
  
  CONCLUSIONS
  The findings indicate that this FFQ estimated higher mean intakes for most nutrients. Pearson's correlation coefficients were comparable with previous research; however, the Bland-Altman plots suggest a high variability in mean nutrient estimates between the FFQ and 24-h. We recommend further investigation of the validity of this FFQ before use.
authors.affiliation: Department of Psychology, Social Work and Public Health, Oxford Brookes University, Oxford, UK.
authors.forename: V
authors.initials: V
authors.lastname: Coathup
authors.affiliation: MRC Epidemiology Unit, University of Cambridge School of Clinical Medicine, Institute of Metabolic Science, Cambridge Biomedical Campus, Cambridge, UK.
authors.forename: S
authors.initials: S
authors.lastname: Wheeler
authors.affiliation: Department of Psychology, Social Work and Public Health, Oxford Brookes University, Oxford, UK.
authors.forename: L
authors.initials: L
authors.lastname: Smith
mesh_terms: D000293:Adolescent; D000328:Adult; D000975:Antioxidants / Q000008:administration & dosage / Q000032:analysis; D001205:Ascorbic Acid / Q000008:administration & dosage / Q000032:analysis*; D001622:Betaine / Q000008:administration & dosage / Q000032:analysis*; D015992:Body Mass Index; D002338:Carotenoids / Q000008:administration & dosage / Q000032:analysis*; D002794:Choline / Q000008:administration & dosage / Q000032:analysis*; D004034:Diet Surveys; D004522:Educational Status; D002149:Energy Intake; D005006:Ethnicity; D005260:Female; D005492:Folic Acid / Q000008:administration & dosage / Q000032:analysis*; D005500:Follow-Up Studies; D006801:Humans; D011939:Mental Recall; D018977:Micronutrients / Q000008:administration & dosage / Q000032:analysis; D015596:Nutrition Assessment; D015203:Reproducibility of Results; D012098:Reproduction / Q000187:drug effects; D011795:Surveys and Questionnaires; D006113:United Kingdom; D044465:White People; D055815:Young Adult
chemical_list: D000975:Antioxidants; D018977:Micronutrients; D002338:Carotenoids; D001622:Betaine; D005492:Folic Acid; D002794:Choline; D001205:Ascorbic Acid