Study on the necessary survey days for energy intake in school children assessed by 7 day survey

Theoretically, the longer the period of a nutrition survey, the more reliable the results. However, a long survey can impose a burden on subjects and cause the results to become inaccurate. For adults, a 3 non-consecutive day survey is usually recommended; however, for school children, at least in Japan, it has not been determined whether this is necessary. In this study we conducted a survey of 7 days and tried to find the minimum number of days necessary to determine the energy intake. The subjects were about 300 children aged from 6 to 7, 10 to 11 and 13 to 14 years old in a city in the western part of Japan. The weighing method was used for the school lunch and other meals were surveyed by 24-recalling method. For the 6-7 year-old school children, guardians were asked to keep dietary records. The final number of subjects who were able to complete the 7-day survey was 139. Energy intakes for each weekday were not statistically different (p>0.05) and those for each weekend did not differ (p>0.05). Average energy intakes on weekdays were higher than those on weekend days in 10-11 and 13-14 year-old children. The average intakes of energy in 10-11 and 13-14 year-old children were lower than Japanese estimated energy requirements (EER). However, body weight of more than 90% of subjects was within the normal range. The results suggest that a survey of one weekday is reliable for all weekdays and that of one week-end day is reliable for any weekend day and also indicate the necessity of further studies of EER in rapidly growing children.