Serum Vitamin D, Folate and Fatty Acid Levels in Children with Autism Spectrum Disorders: A Systematic Review and Meta-Analysis.
Maria Carmen Gallardo-Carrasco, José Antonio Jiménez-Barbero, María Del Mar Bravo-Pastor and 2 others
PMID 34734376WHAT IT FOUND
Children with autism had significantly lower vitamin D levels than controls, but folate levels showed no significant difference.
The vitamin D finding had very high variability between studies, so it should not be treated as a consistent biological marker.
Key findings
01Vitamin D levels were significantly lower in children with ASD compared to controls, with a standardized mean difference of -0.83.
02Folate levels showed no significant difference between children with ASD and controls.
03The vitamin D analysis had very high heterogeneity, with an I-squared value of 92%, indicating substantial inconsistency across the included studies.
STILL TO COME
How it was doneWhat they foundWhat it means for PTsWhat it means for OTsWhat it means for SLPs
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What it does not show
The vitamin D meta-analysis had very high heterogeneity, meaning the pooled effect size may not represent a consistent finding across populations. The folate meta-analysis included only 4 studies with 299 participants, making the null finding less reliable. Fatty acid conclusions rest on a single study and cannot be generalized. The review excluded studies published before 2014, which may omit relevant earlier evidence. The authors could not analyze gender differences because most included studies had predominantly male participants.
Declared interests
The study was funded by Universidad de Murcia. No other conflicts of interest are reported in the provided text.
The easy way to misread this
Do not interpret the significant vitamin D difference as a stable or universal biomarker for autism. The extremely high heterogeneity means the effect varied widely between studies, and subgroup analyses failed to explain this inconsistency. The null folate finding is also based on very few studies and should not be taken as definitive evidence of no association.