Inaccuracy of self-reported low sodium diet

Area of Science:

• Clinical Nutrition
• Renal Physiology
• Dietary Assessment

Background:

• Accurate assessment of sodium (Na) intake is crucial for managing conditions like hypertension.
• Self-reported dietary intake is a common method, but its accuracy in reflecting actual excretion is often questioned.
• 24-hour urinary sodium excretion is considered a more objective measure of sodium intake.

Purpose of the Study:

• To evaluate the concordance between self-reported low sodium intake and measured 24-hour urinary sodium excretion.
• To investigate the impact of incomplete 24-hour urine collections on the accuracy of sodium intake assessment.

Main Methods:

• 120 participants provided self-reported sodium intake (low, medium, high) and underwent 24-hour urine collection for sodium and creatinine measurement.
• Urine collection completeness was defined by creatinine excretion thresholds (men: ≥20 mg/kg, women: ≥15 mg/kg).
• Agreement between self-reported intake and dichotomized 24-hour urinary sodium excretion (≥100 meq) was assessed using the kappa statistic.

Main Results:

• Overall agreement between self-reported and actual sodium excretion was poor (kappa = 0.18).
• Agreement was particularly low for complete urine collectors (kappa = 0.04) but moderate for incomplete collectors (kappa = 0.51).
• A significant proportion of individuals reporting low sodium intake actually exceeded 100 meq/day in their 24-hour excretion, especially with complete collections (80%).

Conclusions:

• Self-reported low sodium intake frequently does not align with measured urinary sodium excretion.
• Incomplete 24-hour urine collections can lead to an underestimation of actual sodium intake.
• Findings highlight the limitations of self-reporting and the challenges posed by incomplete collections in dietary sodium assessment.