Serum Levels of Vitamin D, Retinol and Zinc in Relation to overweight among Toddlers: Findings from a National Study in Iran
Background: Some studies have examined the association between micronutrient deficiencies and overweight in children, but data in this regard are conflicting. This study was done to investigate the association between serum levels of vitamin D, A and zinc with overweight in a large sample of Iranian toddlers. Methods: A total of 4261 toddlers, aged 15-23 months, who had an Iranian birth certificate and attended primary health care, were included in the current cross-sectional study. Weight and height were measured by experts based on standard protocols and body mass index (BMI) was calculated. Based on WHO criteria, overweight was defined as BMI-z-score of ≥1SD. Serum levels of 25(OH)D3 , retinol and zinc were measured for each toddler. Binary logistic regression was applied to assess the association of 25(OH)D3 , retinol and zinc levels with overweight. Results: Mean age of study participants was 19.2 ± 8.4 months. After controlling for potential confounders, children in the highest quartile of serum 25(OH)D3 levels had lower odds of overweight compared with those in the lowest quartile (OR: 0.79, 95% CI: 0.63–0.99). Furthermore, a marginally significant inverse association was found between serum levels of 25(OH)D3 and overweight among urban toddlers (OR: 0.75, 95%CI: 0.56–1.00). Such a relationship was not seen for rural children. No other significant association was seen between serum levels of retinol and zinc and overweight either before or after controlling for covariates. Conclusion: In conclusion, we found a significant inverse association between serum levels of vitamin D and overweight among toddlers. Further studies, particularly of prospective nature, are required to confirm our findings.