Phosphorus intake and potential dietary influences examined via 24h urinary biomarker measurements in German children and adolescents over 3 decades.

BACKGROUND: Increases in phosphorus intake (P-In) have been observed over the past years in adult populations. However, biomarker-based data are lacking on whether P-In also increased in children.

OBJECTIVE: The aim of this study was to examine 24-h urinary phosphate excretion (PO4-Ex) and diet-related biomarkers potentially influencing phosphorus status in German children and adolescents from 1985 to 2015.

DESIGN: This longitudinal noninvasive biomarker-based cohort study examined 24-h urine samples from children and adolescents of the DOrtmund Nutritional and Anthropometric Longitudinally Designed (DONALD) Study, collected over three decades.

PARTICIPANTS: /setting: Examined individuals (n=1057) were healthy participants of the DONALD Study, situated in Dortmund Germany, who had been asked to collect one yearly 24-h urine sample. 6737 samples collected from 3-17 year old participants between 1985 (baseline) and 2015, were included.

MAIN OUTCOME MEASUREMENTS: P-In was examined biomarker-based by analyzed PO4-Ex in 24-h urine samples. Whether acid-base status and intakes of protein, salt, and fruits & vegetables, may have relevantly contributed to PO4-Ex levels was assessed by determining 24-h excretions of net acid, urea-nitrogen, and sodium as well as specific standardized excretions of potassium plus oxalate.

STATISTICAL ANALYSES PERFORMED: Trend analysis over 30 years and potentially influencing diet factors were examined using linear mixed-effect regression models (PROC-MIXED). Adjustments for sex, age and body surface area were performed.

RESULTS: No change was identifiable for PO4-Ex over the 3 decades neither in 3-8, 9-13, nor in 14-17 year-olds, however sodium excretion increased (p=0.001). PROC-MIXED analysis on intra-individual changes in PO4-Ex revealed direct relationships with Net-Acid-Excretion, urea-nitrogen and sodium excretion and an inverse relationship with a biomarker of fruit & vegetable intake.

CONCLUSIONS: Despite a direct relationship between PO4-Ex and a biomarker of industrially-processed food consumption i.e, sodium excretion which showed an increasing time trend, P-In was found to remain stable over decades in children and adolescents.