Abstract
OBJECTIVE: To determine the relative validity of a quantitative FFQ in assessing dietary fluoride intakes using 3 d food and beverage diaries for reference. DESIGN: Parents were asked to complete questionnaires for the preceding week and diaries for 3 d for their children. Fluoride intakes were estimated from 'selected' foods and beverages for questionnaires and from 'all foods and beverages' for diaries. Data collected at 6, 9, 12, 16, 20, 24, 36, 48 and 60 months were analysed cross-sectionally. SETTING: A 3 d food and beverage diary and an FFQ collected through mail from children living in the state of Iowa. SUBJECTS: Children from the Iowa Fluoride Study whose parents completed both an FFQ and a 3 d food and beverage diary at each analysed time point. RESULTS: Correlations between daily mean dietary fluoride intake estimated from questionnaires and diaries range from 0·90 to 0·65. CONCLUSIONS: A quantitative FFQ can provide relative estimates of dietary fluoride intake.