As autism diagnoses continue to rise globally, scientists are exploring all possible causes, including nutrition. One nutrient gaining attention is vitamin D, with new research suggesting it may play a role in both autism risk and symptom severity.
A comprehensive review of multiple studies has found that children with Autism Spectrum Disorder (ASD) tend to have significantly lower vitamin D levels than their neurotypical peers. This finding is raising questions about whether vitamin D deficiency, especially during early development, might be one of the contributing factors to the growing number of autism cases.
Autism on the rise
According to global estimates, the number of children diagnosed with autism has increased manifold in recent decades. While part of the rise is due to better awareness and diagnosis, experts believe environmental and lifestyle factors also play a role. Experts believe that vitamin D deficiency is becoming more common due to increased indoor living, sunscreen use, and poor diets and is responsible for an increase in autism.
What the research says
A new umbrella review that looked at nine separate meta-analyses and systematic reviews found that:
- Children with ASD have lower levels of 25-hydroxyvitamin D [25(OH)D], the main circulating form of vitamin D.
- Vitamin D deficiency in early life was linked to a higher risk of developing autism.
- Supplementation showed positive effects on some autism symptoms, including repetitive behaviours, eye contact, and attention.
Vitamin D is believed to support brain development in several ways. It:
- Reduces inflammation
- Boosts antioxidant levels (like glutathione)
- Supports the growth of nerve cells
- Helps regulate serotonin, a key brain chemical linked to mood and behaviour
- May lower autoimmune and oxidative stress, both of which are thought to contribute to ASD
Results from supplement trials
In one clinical trial, high-dose vitamin D supplements (300 IU/kg/day, up to 5,000 IU per day) were given to children with autism for four months. The results were promising: children showed improvements in behaviour, communication, and social interaction, and no signs of toxicity were observed.
Another review confirmed that supplementation led to better scores on the Childhood Autism Rating Scale (CARS) and showed a trend toward improved social responsiveness.
However, not all studies found consistent results. Differences in dosages, study durations, and small sample sizes made it hard to draw firm conclusions. Experts agree that larger, well-designed clinical trials are needed to figure out the best dosing, timing, and long-term safety of vitamin D for children with autism.
What can be done
Health professionals, especially pharmacists and paediatricians, are encouraged to screen children with autism for vitamin D deficiency, particularly those who get little sun exposure or have restrictive diets. If needed, high-dose supplementation protocols can be considered under medical guidance.
Experts suggest maintaining vitamin D blood levels above 40 ng/mL to potentially see benefits in symptoms. But it’s also important to remember that vitamin D is not a cure, just one possible tool in a larger treatment plan that includes therapy, diet, and behavioural support.
As autism cases rise, vitamin D is emerging as a safe, low-cost, and potentially helpful supplement. While more research is needed, early evidence suggests it may reduce autism risk and help manage certain symptoms. With proper screening and coordination among healthcare providers, vitamin D could become a valuable part of autism care.
