Vitamin D, not iron, is the main nutrient deficiency in pre-school and school-aged children in Mexico City: a cross-sectional study

Introduction: In 2012, the Mexican National Health Survey (ENSANUT 2012) showed a moderate prevalence rate of vitamin D deficiency, around 16%, in a national representative sample of children. A decreasing prevalence of anemia during the last 15 years has been observed in Mexico. The aim of this study was to determine the levels of vitamin D in children 3-8 years old in four different locations within the metropolitan area of Mexico City and to compare them to levels of iron and zinc as references of nutritional status. Methods: One hundred and seventeen healthy children aged 3-8 years attending four hospitals in Mexico City were invited to participate. All children received medical and nutritional evaluation, and blood samples were obtained. Results: Children were selected in four hospitals between April and August 2008. More than half (51.3%) were boys; their average age was 5.5 +/- 1.6 years. The prevalence of subjects with deficient levels of 25-OH-vitamin D (< 50 nmol/L) was 24.77%. None of the children had haemoglobin levels below the anaemia threshold, and zinc determination revealed 8.26% of individuals with deficient levels (<65 mu g/dL). These data confirm the findings reported in ENSANUT about the sustained reduction of anaemia prevalence among preschool and schoolchildren and the rising rates of vitamin D deficiency in the same population. Similar to other studies, we found a link between socioeconomic status and micronutrient deficiency, these being markers of better nutrition, and vitamin D is remarkably related to the quality of the diet. This finding has not been considered in our population before. Conclusions: There is evidence of a sustained decrease of anaemia in Mexican children due to general enrichment of foods and focus on vulnerable populations, while vitamin D deficiency seems to have increased. More studies are needed to obtain more information on vitamin D levels at different ages and definition of susceptible groups in order to investigate the possibility of general population measures such as enrichment, which have proven to be effective.