Variability in nutrient intakes among pregnant women in Indonesia: Implications for the design of epidemiological studies using the 24-h recall method

Few studies have assessed the reliability of dietary intake methods during pregnancy. Between 1996 and 1998, a longitudinal study of dietary intake during pregnancy was carried out among 451 women in Central Java, Indonesia. Six 24-h recalls were performed each trimester. We report here on intraindividual and intraindividual variability in energy and nutrient intakes, as well as the reliability of the 24-h diet recall method. Implications of the use of different numbers of replicate days for estimating dietary intake and the relationships between dietary intake and health outcomes are also discussed. Intravariance-to-intervariance ratios were <1 for energy and carbohydrates and >1 for all other nutrients throughout pregnancy. Reliability analyses found good agreement (reliability coefficient >0.7) with three replicates for the macronutrients, but at least six replicates were needed for an agreement of greater than or equal to0.6 for the micronutrients. To estimate true individual average intake with a precision of +/-20%, six replicate recalls were sufficient for energy, carbohydrates, vitamin A, iron and vitamin C. In conclusion, mean intake of several nutrients can be reliably measured with the 24-h recall method, using a limited number of days. The nutrient of interest, the primary objectives and method of analyses should all be taken into account when planning sample size and number of replicates.