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Discover how vitamin D supplementation may reduce Autism Spectrum Disorder symptoms and improve overall functioning in children with ASD.
Autism Spectrum Disorder (ASD) impacts social communication, behavior, and daily functioning. Emerging evidence suggests vitamin D may influence ASD risk and symptom severity, opening new avenues for prevention and treatment.1
A narrative umbrella review and clinical studies suggest low vitamin D levels are linked to increased autism severity, and high-dose vitamin D supplementation may improve core ASD symptoms in children. | Image Credit: Petr Babkin | stock.adobe.com
An umbrella review of 9 meta-analyses and systematic reviews reported that children with ASD have significantly lower serum 25-hydroxyvitaminD [25(OH)D] levels compared with neurotypical peers. Early-life vitamin D deficiency was highlighted as a strong risk factor for developing ASD, whereas supplementation showed beneficial effects on core ASD symptoms.
Vitamin D may support neurodevelopment through multiple biological pathways. It plays anti-inflammatory roles, increases the neuroprotective antioxidant glutathione, promotes neurotrophin production, and regulates neurotransmitter synthesis—especially serotonin. It also appears to support neuron growth and reduce autoimmune and oxidative stress responses—factors implicated in ASD pathogens.2
A randomized controlled trial involving high-dose vitamin D (300 IU/kg/day, up to 5000 IU/day) in children with ASD documented meaningful improvements in Childhood Autism Rating Scale (CARS) scores, repetitive behaviors, eye contact, and attention after 4 months, without toxicity.3 Similarly, a systematic review and meta-analysis found that vitamin D supplementation led to improvements in stereotyped behaviors and trends toward better social responsiveness and CARS outcomes, although results varied for other core symptoms.4
Despite promising findings, evidence remains mixed. While supplementation improved certain behaviors, effects on broader core symptoms were inconsistent.4 Dosing regimens and trial durations varied widely, and many studies involved small sample sizes. Systematic reviews emphasize the need for large, well-designed randomized controlled trials to clarify optimal dosing, treatment initiation timing, and long-term safety.2,4
Pharmacists should assess patients with ASD for vitamin D deficiency, especially those with limited sun exposure or restrictive diets, and recommend 25(OH)D testing. Based on evidence, high dose vitamin D protocols such as 300 IU/kg/day have demonstrated safety and efficacy.3 Routine evaluation of serum 25(OH)D is important to ensure levels exceed 40 ng/mL, a threshold associated with improved symptom outcomes.4 By explaining neuroimmune mechanisms and the role of vitamin D in ASD pharmacists can help families understand its potential benefits. Emphasizing that supplementation is only 1 component of ASD management is essential. Coordinating care with pediatricians, developmental specialists, and dietitians is important in order to integrate vitamin D strategies into comprehensive treatment plans.
Vitamin D stands out as an affordable, safe, and well tolerated intervention with potential benefit in ASD. Deficiency in early life increases ASD risk, and targeted supplementation has produced improvements in repetitive behaviors and rating scale score. As evidence evolves, pharmacists can lead in translating research into practice—implementing screening, personalized dosing, and interprofessional coordination while awaiting definitive trial results.1-4
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