A step towards using urinary nitrogen as a tool for validating 24-hour dietary recall interviews

Area of Science:

• Nutritional Science
• Clinical Chemistry
• Human Physiology

Background:

• Accurate estimation of dietary protein intake is crucial for assessing nutritional status in active populations.
• Urinary nitrogen excretion is a potential biomarker for protein intake, but its validity in diverse populations requires investigation.

Purpose of the Study:

• To determine if urinary nitrogen output can reliably estimate protein intake in an active population without prior metabolic disease screening.
• To assess the feasibility of comparing protein intake data from 24-hour dietary recalls with 24-hour urinary nitrogen excretion.

Main Methods:

• Forty-five university volunteers consumed a standardized liquid diet for four days.
• A 24-hour urine specimen was collected on the fourth day.
• Protein intake was directly measured and estimated from urinary nitrogen output.

Main Results:

• Estimated protein intake from urinary nitrogen closely matched actual intake for both men (114.5g vs 112.8g) and women (83.9g vs 84.6g).
• Metabolic disease screening appeared unnecessary for this estimation method.
• Overestimation of protein intake occurred in individuals consuming fewer calories than needed.

Conclusions:

• Urinary nitrogen output provides a satisfactory basis for estimating protein intake in active individuals, simplifying assessment protocols.
• The findings support the use of urinary nitrogen as a valid measure for comparing dietary recall data in group studies.
• Caution is advised for individuals with restricted caloric intake, as it may skew protein estimation.