Vitamin D Levels, Frequency of <b><i>Vitamin D Receptor</i></b> Gene Polymorphisms, and Associations with Overweight and Asthma in Brazilian Schoolchildren

<b><i>Background:</i></b> In children, nutritional status of vitamin D (vitD), frequency of <i>vitD receptor (VDR)</i> gene polymorphisms and their associations with overweight and asthma remain controversial. <b><i>Objectives:</i></b> To evaluate the nutritional status of vitD and the frequency of <i>VDR</i> gene polymorphisms, as well as identify their associations with nutritional status and asthma. <b><i>Methods:</i></b> A cross-sectional study was conducted with schoolchildren (<i>n</i> = 262; mean age = 8.7 ± 1.3 years). Clinical history, anthropometric measurements, and serum 25-hydroxy vitD were evaluated. Four <i>VDR</i> gene polymorphisms were identified and genotypes, alleles, and haplotypes were calculated. <b><i>Results:</i></b> The serum vitD levels were found at 85.1%, within normal range. The FokI AA genotype was more frequent in asthmatics compared to healthy controls (10 vs. 1%, <i>p</i> &#x3c; 0.05), while the GG genotype was less frequent (45.0 vs. 55.2%, <i>p</i> &#x3c; 0.05). The frequency of the TT allele for the ApaI was higher among asthmatic eutrophic children (60.9 vs. 29.4%, <i>p</i> &#x3c; 0.05) and that of the TT allele for the BsmI was higher among asthmatic overweight children (35.3 vs. 4.4%, <i>p</i> &#x3c; 0.05). <b><i>Conclusions:</i></b> Insufficiency in vitD was low. Two wild-type alleles (AA) of FokI were identified as risk factor for the development of asthma, while GG alleles appears to be a protective factor. To have polymorphic alleles (TT) of ApaI seems to be a risk factor for asthma in children with normal weight, while that of BsmI seems to be a risk factor for asthma in overweight condition. Serum vitD was not different among analyzed genotypes.