Availability of 24-h urine collection method on dietary phosphorus intake estimation

Abstract

Accurate assessment of dietary phosphorus intake is necessary to prevent hyperphosphatemia. The aim of this study was to evaluate the 24-h urine collection method for estimation of phosphate intake in healthy males. Two experiments, a 1-day and a 5-day loading test, were performed. After an overnight fast, subjects consumed test meals, 24-h urine collection was performed, and blood samples were obtained. In the 5-day loading test, a phosphorus supplement was orally administered on day 3. The association between the phosphorus content of test meals and urinary excretion, anthropometric indices, and blood biomarkers was analyzed to develop a more precise formula for estimating phosphorus intake. In the 1-day loading test, the standard deviation of predictive phosphorus intake, based on multiple linear regression analysis, was less than that for the phosphorus absorption rate. In the 5-day loading test, urinary phosphorus excretion was similar on days 2, 4 and 5, but was significantly higher on day 3 after phosphorus supplementation. Our results indicate that estimation of dietary phosphorus intake with the 24-h urine collection method, using the amount of phosphorus and urea nitrogen excretion, may increase the precision of short-term monitoring.

Twenty-Four-Hour Urine Phosphorus as a Biomarker of Dietary Phosphorus Intake and Absorption in CKD

“…Thus, our results show that for an individual patient, 24-hour urine phosphorus was not reflective of actual phosphorus intake despite a relatively high correlation (r=0.88) between 24-hour urine phosphorus and intake reported in the literature across pooled studies of the general population (27). Recently, large among-subject variation in 24-hour urine phosphorus was also reported in a study of eight young healthy Japanese men on a fixed phosphorus diet (1138 mg/d) over 5 days of 24-hour urine collections (36), which corroborates our findings.…”

The Percentage of Dietary Phosphorus Excreted in the Urine Varies by Dietary Pattern in a Randomized Feeding Study in Adults

“…Despite this, urinary phosphorus excretion has been proposed as a recovery biomarker of total dietary phosphorus intake. An important assumption in the use of urinary phosphorus as a recovery biomarker is that dietary phosphorus intake is excreted at a constant rate in the urine for all individuals, regardless of dietary or nondietary factors (20)(21)(22)(23). Several studies have used a percentage of dietary phosphorus excreted in the urine (percentage phosphorus excretion) of 65% to estimate intake for all individuals (20,21,24), whereas a recent meta-analysis of 14 studies found the mean ± SD percentage phosphorus excretion to be 62.7 ± 17.4% (19).…”

“…An important assumption in the use of urinary phosphorus as a recovery biomarker is that dietary phosphorus intake is excreted at a constant rate in the urine for all individuals, regardless of dietary or nondietary factors (20)(21)(22)(23). Several studies have used a percentage of dietary phosphorus excreted in the urine (percentage phosphorus excretion) of 65% to estimate intake for all individuals (20,21,24), whereas a recent meta-analysis of 14 studies found the mean ± SD percentage phosphorus excretion to be 62.7 ± 17.4% (19). However, the correlation between urinary excretion and selfreported dietary intake ranges from low to moderate in prior studies, with Spearman's correlation coefficients of 0.29-0.53 (19,20,25).…”

Dietary phosphorus intake and blood pressure in adults: a systematic review of randomized trials and prospective observational studies

“…Each of these methods presents its own limitations. Urinary phosphorus excretion has been proposed as a proxy for phosphorus intake and we used it as such in our study (44)(45)(46). However, the dynamic relation between measurements of intake and urinary excretion has not been rigorously characterized.…”