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 interindividual 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 > or =0.6 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.