Methodological approaches for dietary intake assessment in formula-fed infants

The estimation of dietary intake remains a challenge in human nutritional studies. In infants, the use of food diaries (FDs) is a suitable method already validated; however, this method is not exempt from error. In formula-fed infants, dilution of powdered formulas may produce errors. Our aim was to develop and validate standard operating procedures (SOPs) for the assessment of dietary intake in formula-fed infants, attending potential sources of error.

We analysed sources of error in a random subsample of 3-day FDs from 100 infants enrolled in the European Childhood Obesity Project. Calculations to estimate intakes were standardised and included in a software tool (SOPsystem). An evaluation of a simulated FD was performed by 9 trained nutritionists and 23 nutrition students (n=225 and n=575 bottle evaluations, respectively) to compare the results obtained when using or not the SOPsystem. Correct answers (%), coefficients of variation, and the time spent (minutes) to assess the simulated FD were analysed.

Overall, 60% of the FDs contained reports of incorrect volumes, and 37% reported incorrect formula dilutions. When the SOPsystem was used, correct answers in the simulated FD were more frequent (P<0.001) and the mean coefficient of variation and the time spent were lower (P<0.005 and P<0.01, respectively).

The development and implementation of SOPs with a software tool that identifies specific sources of error in record-keeping achieved a harmonised and improved process for assessing dietary intakes in formula-fed infants, minimising errors in calculations and reducing the work time invested.