Urinary fluoride and micronutrients intake in children from San Luis Potosi, Mexico.

To assess the relationship between urinary fluoride and micronutrients intake we recruited 121 schoolchildren from San Luis Potosí. We evaluated fluoride concentrations in drinking water and urine with the ion-selective electrode method and estimated calcium, magnesium, and phosphorus intakes with a validated consumption frequency questionnaire. About 72% of the population used tap water for drinking and cooking. Fluoride concentrations were 2.36 ± 0.02 mg/L in tap water, 0.14 ± 0.04 mg/L in bottled water and 2.05 ± 0.62 mg/L in urine. Urinary fluoride was higher in children with a consumption <50% of the Recommended Daily Intake (RDI) of calcium (2.20 v/s 1.96 mg/L; p < 0.05), <50% RDI of magnesium (2.58 v/s 1.96 and 1.90 mg/L; p < 0.05) and >150% RDI of phosphorus (2.43 v/s 1.82 mg/L; p < 0.05). These data indicated that fluoride concentration in tap water is higher than bottled water and estimated micronutrients intake is related to urinary fluoride.