Use of Urine Biomarkers to Assess Sodium Intake: Challenges and Opportunities

Abstract

This article summarizes current data and approaches to assess sodium intake in individuals and populations. A review of the literature on sodium excretion and intake estimation supports the continued use of 24-h urine collections for assessing population and individual sodium intake. Since 2000, 29 studies used urine biomarkers to estimate population sodium intake, primarily among adults. More than half used 24-h urine; the rest used a spot/casual, overnight, or 12-h specimen. Associations between individual sodium intake and health outcomes were investigated in 13 prospective cohort studies published since 2000. Only three included an indicator of long-term individual sodium intake, i.e., multiple 24-h urine specimens collected several days apart. Although not insurmountable, logistic challenges of 24-h urine collection remain a barrier for research on the relationship of sodium intake and chronic disease. Newer approaches, including modeling based on shorter collections, offer promise for estimating population sodium intake in some groups.

Dietary Sodium and Cardiovascular Disease Risk — Measurement Matters

“…24–26 Analyses showing a J- or U-shaped relationship between sodium intake and one or more cardiovascular outcomes in general population samples used convenient but potentially biased methods to estimate individual intake. 29–32 Multiple, nonconsecutive, 24-hour urine collections are the gold standard for assessing sodium intake.…”

Feasibility of collecting 24-h urine to monitor sodium intake in the National Health and Nutrition Examination Survey

“…The 70% completion rate was chosen in consideration of high respondent burden and the logistic complexity of the component. This is higher than reported completion rates in recent national studies of 24-h urine collections in other industrialized countries (10). With the use of the final MEC response rate for adults aged 20-69 y in the NHANES 2011-2012 (67%) as an estimate of what would be expected in 2013, we estimated that our target completion rate would obtain a final component response rate of 47% (67% 3 70%).…”

“…Although the recovery of para-aminobenzoic acid is considered to be the standard for assessing completeness and was used in the United Kingdom, it is costly and requires participants to take supplements at prescribed times during a specific period, increasing burden and decreasing participation, thus limiting its use in general population surveys (25,26). Similar to our study, other national surveys have used self-report, duration of urine collection, total urine volume, and/or creatinine criteria (post hoc analysis) (10,25). We chose to adapt the protocol used in the International Cooperative Study on Salt, Other Factors, and Blood Pressure, in which completion of the 24-h urine collection was enhanced through explicit instructions and starting and ending the collection in person to ensure accurate timing.…”

“…Completion rates for our feasibility study were higher than those in recent national studies of 24-h urine collections in other industrialized countries, which generally were ,70%, although differences in definitions and protocols between studies limit these comparisons (10). NHANES participants were recruited from the ongoing survey, and their 24-h urine collections were scheduled immediately after the study's physical examination.…”

“…Twenty-four-hour urine sodium excretion is the recommended method for assessing population sodium intake (5,6), yet low participation and difficulty in completing collection potentially can bias estimates (6,7). As with sodium intake, urinary sodium excretion varies from day to day, which complicates the use of sodium excretion to estimate excess sodium intake (8)(9)(10). To take within-individual variation into account, .1 nonconsecutive day is needed to estimate the distribution of sodium intake, and, in particular, the percentage of the population with excess sodium intake.…”