Relative validation of a pre-coded food diary among children, under-reporting varies with reporting day and time of the day

Abstract

The aim of this study was to validate intake of energy, macro- and micronutrients assessed from pre-coded food diaries (PFDs) by using weighed records (WRs) as the reference method among a group of Norwegian 9-year-olds. We also examined how under-reporters (UR) differed from acceptable reporters (AR) according to the energy intake during the 4-day recording period and energy intake distribution during the day. One hundred 9-year-olds, 45 girls and 55 boys, were recruited to complete a 4-day record with a PFD followed 3 days later with a 4-day WR. There were no differences between energy and nutrient intake from the two recording methods among boys, but girls reported significantly higher intakes with PFD compared with WR. The median Spearman correlation coefficient between PFD and WR for energy and nutrients was 0.43 for girls and 0.49 for boys. Twelve participants were classified as UR with the PDF method. Energy percentages from macronutrients were not significantly different between UR and AR with the PFD method. UR had significantly lower energy intake in the last two recording days and from 1000 to 2200 hours during the day compared to AR. The PFD method is promising as a tool for assessing food intake in large surveys among children. The present study indicates that the PFD gives more valid data for boys than girls according to the group intake and ranking of nutrient intake when WR is the reference method. However, UR seemed to develop a study fatigue during the day and during the recording period. Increased awareness about the tendency of study fatigue can lead to more specific instructions on how participants can handle the problem.