Iodine nutritional status in urban and rural Mexican schoolchildren.

Introduction: Deficient or excess iodine intake has effects on human health. Assessment of the prevalence and risk factors in children can therefore support effective prevention or treatment.

Method: A cross-sectional probabilistic study in 631 children aged 5 to 12 years in whom iodine levels were measured in urine and salt samples. Results are reported by type of location and indigenous condition. Association of these variables to urinary iodine levels was assessed using a binary logistic regression.

Results: Median urinary iodine level was 278.4μg/L (177.3-360.9, IQR), 13.2% of children assessed had iodine levels <100μg/L, and 41.8% had values ≥300μg/L. Indigenous schoolchildren had the greatest risk of urinary iodine levels <100μg/L (β = 2.29, CI 1.1-4.6, p <.05), while children from urban and non-indigenous localities had a high risk of iodine levels >300μg/L (β = 2.2, CI 1.3 -3.9, p <.01, and β = 3.8, CI 2.2-6.5, p <.01 respectively). Median iodine level in salt was 35.9ppm (29.1-42.4 IQR), and there were no differences in iodine levels in salt by type of location or ethnicity.

Conclusions: In Mexican schoolchildren living in rural and indigenous areas, iodine levels <100μg/L have not been eradicated. There was high prevalence of urinary iodine levels ≥300μg/L in schoolchildren living in urban areas which was associated to high sodium intake from processed food.