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 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 the four hospitals between April and August 2008. More than half (51.3%) were boys; their average age was 5.5 ± 1.6 years. The mean height and weight of the children were 112.1 ± 11.2 cm and 20.2 ± 4.9 kg respectively, with a body mass index [BMI] of 15.8 ± 1.7 kg/m². The mean Z-score (BMI) was 0.007 ± 0.999. 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 µg/dL). These data confirm the findings reported in the latest National Nutrition Survey (ENSANUT 2012) about the sustained reduction of anaemia prevalence among preschool and schoolchildren since 1999 and the rising rates of vitamin D deficiency in the same population. Similar to other studies, we found a link between socioeconomic status and the deficiency of micronutrients, 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.