Measurement error corrected sodium and potassium intake estimation using 24-hour urinary excretion

Area of Science:

• Nutritional Epidemiology
• Biomarker Validation
• Cardiovascular Disease Risk Factors

Background:

• Epidemiological studies on sodium and potassium intake and cardiovascular disease risk often rely on self-reported dietary data, which are prone to measurement error.
• 24-hour urinary excretion assessments offer a more objective biomarker for sodium and potassium intake compared to self-reports.

Purpose of the Study:

• To develop and validate calibration equations to correct self-reported dietary data for sodium and potassium using 24-hour urinary excretion.
• To assess the accuracy of different dietary assessment methods (food frequency questionnaires, food records, 24-hour recalls) in estimating sodium and potassium intake.

Main Methods:

• Utilized data from the Women's Health Initiative studies, comparing self-reported intake with 24-hour urinary excretion biomarkers.
• Developed calibration equations using linear regression, incorporating subject characteristics like race, age, and body mass index.
• Adjusted for temporal variation in biomarker measurements.

Main Results:

• Self-reported dietary data significantly underestimated sodium and overestimated potassium intake compared to urinary excretion.
• Calibration equations derived from food records and recalls showed moderate to good explanatory power for sodium (45-50%), potassium (60-70%), and their ratio (55-60%).
• Food frequency questionnaire data yielded weaker calibration signals, but equations for nutrient/energy ratios showed some utility.

Conclusions:

• Calibration equations using 24-hour urine data can improve the accuracy of self-reported sodium and potassium intake for epidemiological studies in postmenopausal women.
• Food records and recalls are more suitable than food frequency questionnaires for calibration, though cautious use of FFQ-derived equations is possible.
• Accurate dietary assessment is crucial for understanding the relationship between sodium, potassium, and cardiovascular disease risk.