The development and evaluation of a food frequency questionnaire used in assessing vitamin D intake in a sample of healthy young Canadian adults of diverse ancestry ☆ Hongyu Wu a , Agnes Gozdzik b , Jodi Lynn Barta b , Dennis Wagner c,e , David E. Cole d , Reinhold Vieth c,e , Esteban J. Parra b , Susan J. Whiting a, ⁎ a College of Pharmacy and Nutrition, University of Saskatchewan, Saskatoon SK, Canada S7N 5C9 b Department of Anthropology, University of Toronto at Mississauga, Mississauga, Ontario, Canada L5L 1C6 c Department of Nutritional Sciences, University of Toronto, Toronto, Ontario, Canada M5S 3E2 d Departments of Laboratory Medicine and Pathobiology, Medicine, and Paediatrics (Genetics), University of Toronto, Toronto, Ontario, Canada M5G 1L5 e Department of Pathology and Laboratory Medicine, Mount Sinai Hospital, Toronto, Ontario, Canada M5G 1X5 Received 8 January 2009; revised 23 March 2009; accepted 23 March 2009 Abstract Little data exist on vitamin D deficiency related with intake, especially for the Canadian population. The purpose of this study was to develop and evaluate a food frequency questionnaire (FFQ) with 37 items for rapid assessment of vitamin D intake in healthy young adults of diverse ancestry. We recruited 107 subjects in Southern Ontario during the late winter of 2007 who completed an FFQ twice (FFQ-1 and FFQ-2, repeated for reproducibility assessment) and a 7-day food diary (for validation). Serum 25- hydroxyvitamin D (25(OH)D), the major biomarker of vitamin D nutritional status, and skin melanin were determined. The FFQ results were highly correlated with 7-day diary results and with serum 25 (OH)D concentrations (r = 0.529, P b .001; r = 0.481, P b .001, respectively). Modifications to the FFQ, by redefining the large serving size and excluding the fortified orange juice category, improved the validity of the FFQ (r = 0.602, P b .001; r = 0.520, P b .001, respectively). The FFQ results were highly correlated (r = 0.663, P b .001), but the mean intakes were different (P b .05). Using results from a modified version of FFQ-1, we examined dietary intakes in 3 predominant groups: East Asian (n = 27), European (n = 31), and South Asian (n = 32). The European group had higher total vitamin D intake (P b .05) and the highest serum 25(OH)D concentrations (P b .05), with a trend for dairy products being responsible for this (P b .10). Because Canadians are reliant on dietary intakes of vitamin D in the wintertime, especially those with higher skin melanin, our FFQ can monitor and provide information on intake and food group consumption. © 2009 Elsevier Inc. All rights reserved. Keywords: Human, Vitamin D; Nutrition assessment; Diet surveys; Adults; Ethnic groups Abbreviations: 25(OH)D, 25-hydroxyvitamin D; BMI, body mass index; FFQ, food frequency questionnaire; κw, weighted kappa; LSD, least significant difference (a post-hoc multiple comparison test); PTH, parathyroid hormone; SD, standard deviation. Available online at www.sciencedirect.com Nutrition Research 29 (2009) 255 – 261 www.nrjournal.com ☆ SW has received honoraria from the Dairy Farmers. RVand DEC have received funding from the Dairy Farmers of Canada. RV has served as a consultant to or has received honoraria from Cytochroma, Ddrops Company, Merck, Novartis, and Wyeth. ⁎ Corresponding author. E-mail address: susan.whiting@usask.ca (S.J. Whiting). 0271-5317/$ – see front matter © 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.nutres.2009.03.006