Development and validation of a short questionnaire for estimating the intake of zinc

Zinc is an essential nutrient required for numerous metabolic functions. The aim of the present study was to develop a zinc-specific food frequency questionnaire (FFQ) and to determine its relative validity. A 74-item FFQ was designed for the measurement of zinc intake. Food items were included in the FFQ if their zinc content was >0.5 mg/100 g, and the food item contributed >5% of the recommended dietary intake. Female subjects (n = 22) were recruited to complete the questionnaire in addition to maintaining a weighed food record for 7 days. Mean intake of zinc obtained from the weighed records (8.8 +/- 2.3 mg/day; mean +/- SD) was significantly lower than that obtained from the FFQ (10.5 +/- 3.1 mg/day; P < 0.01). Ranked zinc intakes obtained from the two instruments were significantly correlated (r (s) = 0.81, P < 0.001). Evaluation of progressively shortened versions of the FFQ, containing 23-61 food items and representing 60-90% of the contribution to total zinc intake, yielded correspondingly decreasing magnitudes of zinc intake, but the rank correlation with the weighed records was significant (P < 0.01). Rank correlations and analysis of plots from Bland-Altman analyses suggest that a shortened 37-item FFQ has comparable validity to the full FFQ. A shortened FFQ is likely to produce lower demands on the interviewer and/or respondent when assessing zinc intake.