The influence of survey duration on estimates of food intakes and its relevance for public health nutrition and food safety issues

Objective: To examine the influence of food consumption survey duration on estimates of percentage consumers, mean total population intakes and intakes among consumers only and to consider its relevance for public health nutrition and food safety issues. Design: Prospective food consumption survey. Setting: A multicentre study in five centres in the European Union-Dublin, Ghent, Helsinki, Potsdam and Rome. Subjects: Teenage subjects were recruited through schools; 948 (80%) out of 1180 subjects completed the survey. Interventions: 14-day food diaries were used to collect the food consumption data. Results: For mean total population intakes, 53% of the foods had slopes significantly different to 0 (P<0.05). In practical terms (g/day), these differences were small, with 41% of foods having differences of ≤ 1 g/day and a further 35% having differences of 1-5 g/day. Estimates of percentage consumers based on 3 days and 14 days were 1.9 and 3.6 times the 1-day estimate, respectively. For 72% of foods, at least 50% of non-consumers on day 1 became consumers over the subsequent 13 days. Estimates of mean consumer only intakes based on 3 days and 14 days were 53% and 32% of the 1 day value. Conclusion: In practical terms, survey duration influences estimates of percentage consumers and intakes among consumers only but not mean total population intakes. Awareness of this influence is important for improved interpretation of dietary data for epidemiological studies, development of food-based dietary guidelines and food chemical intakes.