24-hour national dietary survey data: how do we interpret them most effectively?

Area of Science:

• Nutritional epidemiology
• Dietary assessment methodology

Background:

• National dietary surveys are crucial for assessing population nutrient intake.
• Common analytical methods may introduce biases in estimating nutrient inadequacy.
• Accurate estimation of nutrient intake prevalence is vital for public health nutrition.

Purpose of the Study:

• To demonstrate the impact of common analytical errors on 24-hour dietary survey data.
• To illustrate how these errors affect the estimation of inadequate nutrient intakes.
• To highlight the importance of appropriate statistical adjustments and reference standards.

Main Methods:

• Utilized raw nutrient intake data from the Australian 1995 National Nutrition Survey.
• Adjusted data for within-person variance using standard statistical techniques.
• Corrected for underreporting using the Goldberg et al. criteria.
• Compared nutrient distributions with dietary reference values from the UK, USA, and Australia.

Main Results:

• Adjusting for within-person variance reduced the range of nutrient intakes and the proportion below the Estimated Average Requirement (EAR) by up to 20%.
• Excluding underreporters further decreased the proportion below the EAR by up to 10%.
• Estimates of nutrient inadequacy varied significantly based on the dietary reference values used, with folate prevalence ranging from <1% to 92% for adult women.
• Prevalence of low intakes was generally higher in women than men, except for vitamin A and protein.

Conclusions:

• Estimates of low nutrient intake prevalence derived from raw 24-hour survey data are unreliable.
• Even after adjustments for variance and underreporting, estimates can remain misleading.
• Interpretation requires careful consideration of the reference criteria and supporting biochemical/physiological data.