Monitoring caffeine intake in children with a questionnaire and urine collection: a cross-sectional study in a convenience sample in Switzerland.

Purpose: The objectives of this study were (1) to estimate caffeine intake and identify the main sources of intake using a dietary questionnaire, (2) to assess 24-h urinary excretion of caffeine and its metabolites, and (3) to assess how self-reported intake estimates correlates with urinary excretion among children in Switzerland. Methods: We conducted a cross-sectional study of children between 6 and 16 years of age in one region of Switzerland. The participants filled in a dietary questionnaire and collected a 24-h urine sample. Caffeine intake was estimated with the questionnaire. Caffeine, paraxanthine, theophylline, and theobromine excretions were measured in the urine sample. Correlations between questionnaire-based intake and urinary excretion estimates were assessed using Spearman correlation coefficients. Results: Ninety-one children were included in the analysis (mean age 10.6 years; 43% female). The mean daily caffeine intake estimate derived from the diet questionnaire was 39 mg (range 0–237), corresponding, when related to body weight, to 1.2 mg/kg (range 0.0–6.3). Seven children (8%) had a caffeine intake above the upper recommended level of 3 mg/kg per day. The main sources of caffeine intake were cocoa milk (29%), chocolate (25%), soft drinks (11%), mocha yogurt (10%), tea (8%), and energy drinks (8%). The 24-h urinary excretion of caffeine was 0.3 mg (range 0.0–1.5), paraxanthine 1.4 mg (range 0.0–7.1), theophylline 0.1 mg (range 0.0–0.6), and theobromine 14.8 mg (range 0.3–59.9). The correlations between estimates of caffeine intake and the 24-h urinary excretion of caffeine was modest (ρ = 0.21, p = 0.046) and with the metabolites of caffeine were weak (ρ = 0.09–0.11, p = 0.288–0.423). Conclusions: Caffeine intake in a sample of children in a region of Switzerland was relatively low. The major sources of intake were cocoa milk, chocolate and soft drinks. Self-reported caffeine intake correlated weakly with urinary excretion of caffeine and some of its main metabolites. Trial registration number: NCT02900261. [ABSTRACT FROM AUTHOR]