title: VALIDITY OF A FOOD-FREQUENCY QUESTIONNAIRE FOR ESTIMATING CALCIUM INTAKE IN ADOLESCENT SWIMMERS.
abstract: BACKGROUND
  accurate estimates of the intake of specific nutrients such as calcium (Ca) are crucial to correctly rank or classify subjects in the distribution of intakes. Therefore, we aimed to estimate the relative validity of a food frequency questionnaire (FFQ) for measuring Ca intake in two different groups of healthy adolescents, a normoactive control group and a physically active group of swimmers with 2 non-consecutive 24h recalls (2 x 24HR) collected as the reference method.
  
  
  METHODS
  Pearson correlations, agreement between the 24HR and the FFQ at an individual level and questionnaire's ability to assign individuals to the same quartile of intake as the 24HR were calculated.
  
  
  RESULTS
  mean daily Ca intakes were 564.6 mg (SD 232.0) and 895.9 mg (SD 343.1) for the 2 x 24HR and FFQ respectively in controls (P < 0.001); and 731.9 mg (SD 299.8) and 979.8 mg (SD 408.5) for the 2 x 24HR and FFQ respectively in swimmers (P < 0.001). Pearson correlations were 0.52 for controls and 0.47 for swimmers after correcting for intra-variability. Cross-classification analysis indicated that 73.7% of controls and 63.1% of swimmers were classified correctly or in the adjacent category. Also, the 89% of the control group and 79% of swimmers were classified correctly with the FFQ according to the dietary reference intake (DRI) of 1300 mg/d.
  
  
  CONCLUSIONS
  for both groups, the FFQ tended to overestimate Ca intake, however it demonstrated fairly good ability to classify subjects into extremes of Ca intake and identified adolescents having Ca intakes lower than the dietary reference intake.
authors.affiliation: GENUD "Growth, Exercise, NUtrition, and Development", University of Zaragoza (Zaragoza), Spain. Faculty of Health and Sport Science (FCSD), Department of Physiatry and Nursing, University of Zaragoza (Huesca), Spain.. cjulian@unizar.es.
authors.forename: Cristina
authors.initials: C
authors.lastname: Julián Almárcegui
authors.affiliation: Dietary Exposure Assessment Group, International Agency for Research on Cancer, Lyon, France. Faculty of Medicine and Health Sciences, Department of Public Health, Ghent, Belgium.. huybrechtsi@iarc.fr.
authors.forename: Inge
authors.initials: I
authors.lastname: Huybrechts
authors.affiliation: GENUD "Growth, Exercise, NUtrition, and Development", University of Zaragoza (Zaragoza), Spain. Faculty of Health and Sport Science (FCSD), Department of Physiatry and Nursing, University of Zaragoza (Huesca), Spain.. bruton@unizar.es.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Gómez Bruton
authors.affiliation: GENUD "Growth, Exercise, NUtrition, and Development", University of Zaragoza (Zaragoza), Spain. Faculty of Health and Sport Science (FCSD), Department of Physiatry and Nursing, University of Zaragoza (Huesca), Spain.. amatute@unizar.es.
authors.forename: Ángel
authors.initials: Á
authors.lastname: Matute Llorente
authors.affiliation: GENUD "Growth, Exercise, NUtrition, and Development", University of Zaragoza (Zaragoza), Spain. Department of Sport and Exercise Science, Aberystwyth University, Aberystwyth, United Kingdom.. alg28@aber.ac.uk.
authors.forename: Alejandro
authors.initials: A
authors.lastname: González Agüero
authors.affiliation: GENUD "Growth, Exercise, NUtrition, and Development", University of Zaragoza (Zaragoza), Spain. Centro Universitario de la Defensa, Zaragoza, Spain.. agomez@unizar.es.
authors.forename: Alba
authors.initials: A
authors.lastname: Gómez Cabello
authors.affiliation: GENUD "Growth, Exercise, NUtrition, and Development", University of Zaragoza (Zaragoza), Spain. Faculty of Health Sciences, University of Zaragoza (Zaragoza), Spain.. lmoreno@unizar.es.
authors.forename: Luis A
authors.initials: LA
authors.lastname: Moreno
authors.affiliation: GENUD "Growth, Exercise, NUtrition, and Development", University of Zaragoza (Zaragoza), Spain. Faculty of Health and Sport Science (FCSD), Department of Physiatry and Nursing, University of Zaragoza (Huesca), Spain.. joseant@unizar.es.
authors.forename: Jose A
authors.initials: JA
authors.lastname: Casajús
authors.affiliation: GENUD "Growth, Exercise, NUtrition, and Development", University of Zaragoza (Zaragoza), Spain. Faculty of Health and Sport Science (FCSD), Department of Physiatry and Nursing, University of Zaragoza (Huesca), Spain.. gervicen@unizar.es.
authors.forename: Germán
authors.initials: G
authors.lastname: Vicente Rodríguez
mesh_terms: D000293:Adolescent; D002136:Calcium, Dietary / Q000008:administration & dosage*; D004034:Diet Surveys; D005247:Feeding Behavior; D005260:Female; D006801:Humans; D008297:Male; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires; D013550:Swimming / Q000502:physiology*
chemical_list: D002136:Calcium, Dietary