Diet Data Collected Using 48-h Dietary Recall: Within-and Between-Person Variation

Area of Science:

• Nutrition Science
• Dietary Assessment Methods
• Biostatistics

Background:

• Forty-eight-hour dietary recall is a common method for assessing population food consumption.
• The optimal number of assessments and sample size for estimating usual intake remain unclear.
• Understanding variation is crucial for accurate dietary assessment.

Purpose of the Study:

• To assess sources of variation in dietary intake using 48-hour recalls.
• To determine the necessary sample sizes and number of days for estimating usual nutrient intake.
• To evaluate the impact of within- and between-person variation on these estimates.

Main Methods:

• Population-based cross-sectional study with 237 participants (11-90 years old).
• Multistage probabilistic sampling used for participant selection.
• Analysis of variance (ANOVA) employed to calculate variation and statistical parameters for sample size determination.

Main Results:

• Within-person variation was generally lower than between-person variation, with exceptions for calcium, magnesium, and monounsaturated fat.
• Required sample size and number of days varied significantly by gender and age (e.g., Vitamin C: 9 women vs. 1,641 men).
• Inadequate assessment of within-person variation may affect sample size and day calculations.

Conclusions:

• Forty-eight-hour dietary recall can misrepresent within-person variation but yield acceptable between-person variation estimates.
• Accurate estimation of usual energy and nutrient intake depends on correctly assessing within-person variation.
• Further research is needed to refine sample size and duration calculations for dietary recall studies.