Background: Studies have consistently found a high prevalence of vitamin D deficiency in adolescents. Few validated dietary intake assessment tools for vitamin D exist for adolescents.
Objective: The aim of this study was to determine if a short food frequency questionnaire (SFFQ) can be used to effectively assess vitamin D intake in adolescents compared to a previously validated long food frequency questionnaire (LFFQ).
Participants/setting: 140 healthy 6-12 year old (male n=81) Caucasian and African American (n=94) children from Pittsburgh, Pennsylvania completed a SFFQ and LFFQ at two time points 6 months apart.
Main outcome measures: Reliability and validity of a SFFQ by comparison with a previously validated LFFQ for children and adolescents.
Statistical analysis: Reliability, validity, sensitivity, specificity, positive, and negative predictive values were assessed using Pearson correlation coefficients.
Results: Mean vitamin D intake from the SFFQ (range, 434 to 485 IU) was higher than the LFFQ (range, 320 to 378 IU). Overall association between the SFFQ and the LFFQ for vitamin D intake was modest (r=0.36, P<0.001). When stratified by race, the overall degree of association was weak for African Americans (r=0.26, P=0.001) and moderate for Caucasians (r=0.57, P<0.001). Overall reliability testing results were modest and significant for the LFFQ (r=0.28, P=0.002) and SFFQ (r=0.33, P<0.001). Association between mean vitamin D intake from LFFQs and SFFQs was used to determine validity. The association for validity was found to be modest (r=0.51, P<0.001). Sensitivity, specificity, positive predictive value, and negative predictive value for the SFFQ were 90%, 64%, 0.78, and 0.58, respectively.
Conclusion: The SFFQ was found to be modestly valid and reliable in an early adolescent population. Associations between African Americans were not as strong as Caucasians which may be due to errors in reporting dietary consumption related to higher body weight.
Available at: http://works.bepress.com/caitlin_russell/1/