title: Development, validation and implementation of a quantitative food frequency questionnaire to assess habitual vitamin D intake.
abstract: A well-designed, validated quantitative food frequency questionnaire (FFQ) could offer an efficient and cost-effective method for assessing habitual vitamin D intake. The present study aimed to describe the development, validation and implementation of a vitamin D FFQ.
  
  
  
  National food consumption survey data obtained from Irish adults (18-64 years) were used to identify foods that contribute 95% of vitamin D intake. A winter-based validation study was carried out for the resulting FFQ in 120 females, including 98 women [mean (SD) 65.0 (7.3) years] and 22 girls [12.2 (0.8) years], using a 14-day diet history (DH) as a comparator. Serum 25(OH)D concentrations were analysed. Validity coefficients were calculated using the method of triads. Cross-classification and Bland-Altman analysis were also performed.
  
  
  
  Median (interquartile range) vitamin D intakes (including the contribution from nutritional supplements) were 5.4 (3.7) and 3.7 (5.9) μg day(-1) from the FFQ and DH, respectively and intakes of vitamin D from food sources were 3.6 (3.1) and 2.4 (2.2) μg day(-1) . The FFQ and DH classified 86% and 87% of individuals into the same and adjacent thirds of wintertime serum 25(OH)D status, respectively. There was a strong association (r = 0.71, P < 0.0001) and no significant systematic or proportional bias observed for the difference between estimates from the FFQ and DH. The validity coefficient for the FFQ was 0.92 (95% confidence interval = 0.80-0.97). Repeatability analysis (n = 56) performed 6-12 months later showed no significant difference in estimates of vitamin D between administrations.
  
  
  
  The data obtained in the present study indicate high validity and good reproducibility of a short, interviewer-administered FFQ for vitamin D.
authors.affiliation: Vitamin D Research Group, School of Food and Nutritional Sciences, University College Cork, Cork, Ireland.|The Irish Centre for Fetal and Neonatal Translational Research (Infant), University College Cork, Cork, Ireland.
authors.forename: M
authors.initials: M
authors.lastname: Kiely
authors.affiliation: Vitamin D Research Group, School of Food and Nutritional Sciences, University College Cork, Cork, Ireland.
authors.forename: A
authors.initials: A
authors.lastname: Collins
authors.affiliation: Vitamin D Research Group, School of Food and Nutritional Sciences, University College Cork, Cork, Ireland.
authors.forename: A J
authors.initials: AJ
authors.lastname: Lucey
authors.affiliation: National Food Institute, Technical University of Denmark, Copenhagen, Denmark.
authors.forename: R
authors.initials: R
authors.lastname: Andersen
authors.affiliation: Vitamin D Research Group, School of Food and Nutritional Sciences, University College Cork, Cork, Ireland.|Department of Medicine, University College Cork, Cork, Ireland.
authors.forename: K D
authors.initials: KD
authors.lastname: Cashman
authors.affiliation: Vitamin D Research Group, School of Food and Nutritional Sciences, University College Cork, Cork, Ireland.
authors.forename: Á
authors.initials: Á
authors.lastname: Hennessy
mesh_terms: D000293:Adolescent; D000368:Aged; D002648:Child; D000072001:Diet, Healthy; D019587:Dietary Supplements; D005247:Feeding Behavior; D005260:Female; D005518:Food Preferences; D006801:Humans; D007494:Ireland / Q000453:epidemiology; D008875:Middle Aged; D015596:Nutrition Assessment; D009749:Nutrition Surveys; D010349:Patient Compliance; D015995:Prevalence; D015203:Reproducibility of Results; D012306:Risk; D012621:Seasons; D057566:Self Report; D014807:Vitamin D / Q000031:analogs & derivatives / Q000097:blood / Q000627:therapeutic use*; D014808:Vitamin D Deficiency / Q000097:blood / Q000453:epidemiology / Q000517:prevention & control*
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D
keywords: bone health; dietary assessment; food frequency questionnaire; vitamin D