Halenur TEKE, Hilal TÜTER MAVİ, Ahmet BOLAT, Melikşah Safa ÜÇOK, Şahin BODUR, Mehmet Ayhan CÖNGÖLOĞLU
Journal of Health Sciences and Medicine - 2026;9(5):1370-1378
Aims: This study aimed to compare serum 25-hydroxyvitamin D [25(OH)D], vitamin B12, and folate concentrations between children with autism spectrum disorder (ASD) and typically developing controls, and to examine their relationship with autism symptom severity. Methods: This case-control study combined prospective clinical evaluation with retrospective retrieval of routine serum 25(OH)D, vitamin B12, and folate measurements from electronic medical records. The study included 140 children aged 2-8 years, comprising 70 children with ASD and 70 age- and gender-comparable typically developing controls, at a tertiary university hospital in Turkiye. ASD diagnosis was established according to DSM-5 criteria, and symptom severity was assessed using the Childhood Autism Rating Scale (CARS). Group comparisons, correlation analyses, and multivariable linear regression were performed. Results: Children with ASD had lower mean serum 25(OH)D concentrations than controls (mean difference: -3.43 ng/ml, 95% CI: -6.07 to -0.79; Cohen's d=-0.43; p=0.011). Vitamin B12 and folate concentrations did not differ significantly between groups. The frequencies of vitamin D, vitamin B12, and folate deficiencies were also comparable between the ASD and control groups. Within the ASD group, none of the evaluated micronutrients differed by ASD severity or correlated with CARS scores. In the multivariable linear regression analysis, ASD group status and season of blood sampling remained independently associated with serum 25(OH)D concentrations after adjustment for age, gender, and body-mass index z-score. Conclusion: Children with ASD had lower mean serum 25(OH)D concentrations than typically developing controls, although vitamin D deficiency rates were comparable between the groups. This finding suggests that vitamin D status may warrant attention as a modifiable aspect of nutritional health in this population but should not be interpreted as an ASD-specific biomarker. Longitudinal and intervention-based studies are needed to clarify the directionality and clinical significance of this association and the potential benefit of supplementation in ASD.
