Urinary Magnesium, Calcium, and Phosphorus to Creatinine Ratios of Healthy Elementary School Lebanese Children

Urinary magnesium (Mg), calcium (Ca), and phosphorus (P) excretions are known to vary greatly between populations due to dietary habits, physical activity, mineral content of water, climate, genetics, and race. Thus, it is essential to determine the normal values in each population in order to assess the status as well as to diagnose any possible abnormality of metabolisms especially hypercalciuria. A study was conducted to determine urinary Mg/creatinine (Cr), Ca/Cr, and P/Cr ratios of healthy Lebanese elementary schoolchildren. Using a multi-stage cluster sampling at district, school, and class levels, a sample of 1403 children (781 boys and 622 girls), from 26 different schools, was selected. Non-fasting morning urine samples and anthropometric data were collected and analyzed. The mean Mg/Cr, Ca/Cr, and P/Cr ratios were 0.122 ± 0.075 mg/mg (0.568 ± 0.348 mM/mM), 0.084 ± 0.101 mg/mg (0.237 ± 0.286 mM/mM), and 0.692 ± 0.417 mg/mg (2.527 ± 1.524 mM/mM), respectively, with no significant difference between boys and girls (P = 0.706, 0.161, and 0.604; respectively). The 95th percentile of Mg/Cr, Ca/Cr, and P/Cr ratios fluctuated with age, showing a sharp decrease in Ca/Cr and P/Cr at the age of 10. The mean Mg/Cr, Ca/Cr, and P/Cr ratios were comparable to those of similar age groups in other populations. The 95th percentiles of Mg/Cr, Ca/Cr, and P/Cr ratios were 0.26 mg/mg (1.23 mM/mM), 0.27 mg/mg (0.76 mM/mM), and 1.48 mg/mg (5.40 mM/mM), respectively. These values can be used as cutoffs to detect abnormalities in these three minerals' metabolisms among healthy Lebanese children.