While scientists are still in the dark about what exactly causes autism, genetics and environmental factors (early exposure to heavy metals, pesticides, infections and other toxins) are cited as some of the main risk factors. Complications experienced in pregnancy and delivery may also make a new-born more susceptible to develop this neurodevelopmental condition.
Could low vitamin D levels be a potential risk factor here? Research so far does indicate that the risk of autism spectrum disorder (ASD) may be linked with low vitamin D status.
A study by the Queensland Brain Institute reported that vitamin D deficiency during pregnancy can increase the risk of a child with autistic features. The study hinted that inadequacy of the sunshine vitamin during fetal development could be one contributing risk factor for autism. However, not all babies born to mothers with low vitamin D levels develop autism. That’s why some experts believe that insufficient vitamin D in the womb may not be the only causative factor. It must be working along with genetics or environmental influences to increase the probability.
Can Vitamin D supplements help reduce autism risk?
Professor John McGrath, the lead researcher of the study said the results can be likened to the effect of taking folate in pregnancy on the risk of spina bifida in babies. The study concluded,
“25OHD deficiency assessed either at mid-gestation or at birth was associated with an increase in autism-related traits in 6-year-old children…….…. It is feasible that a safe, cheap and publicly accessible vitamin D supplement in at-risk groups may reduce the prevalence of this risk factor. Just as prenatal folate supplementation has reduced the incidence of spina bifida, we speculate that prenatal vitamin D supplementation may reduce the incidence of ASD.” 
Can Vitamin D supplements benefit children with autism?
Autistic children have been found to have lower levels of vitamin D than other children. Studies also report vitamin D deficiency in children with the disorder. Could vitamin D supplementation help manage the condition or alleviate symptoms?
A recent double-blind, randomized clinical trial explored the effect of vitamin D supplements on children with autism. 109 children (85 boys and 24 girls; aged 3–10 years) with ASD received vitamin D3 or placebo for 4 months. The study found a significant improvement in autism symptoms, such as hyperactivity and social withdrawal in children who received the supplementation. The same effect was not observed in the placebo group.
The study concluded that, “oral vitamin D supplementation may safely improve signs and symptoms of ASD and could be recommended for children with ASD.” The study authors emphasised the need of more wide-scale studies to validate the worth of vitamin D in autism. 
The results are indeed promising but not all experts agree with these findings. They believe it may be too early to draw any significant conclusions from this small data. There is definitely a need to reproduce these findings on a much larger scale. However, the evidence linking low vitamin D levels with the increased risk of neurodevelopmental disorders such as autism, is fast growing.
A study of 800,000 children in Scotland hinted at an interesting likelihood. It found that children conceived in winter months are at an increased risk of developing autism and other learning disorders than those conceived in summers. The researchers speculated that scarcity of sunlight, hence vitamin D deficiency, during the first trimester could be the reason behind this finding.  It is the time when fetal brain development is taking place at a fast pace. And vitamin D has come across as a critical and multi-faceted player in the development of fetal lungs, brain, and bone in many studies.
There has been a dramatic rise in the number of autism cases. Keeping in mind that vitamin D supplements are cheap, well tolerated and safe, all these findings and research present exciting possibilities in reducing risk and manage this ‘incurable’ condition. Right now, there is no cure for autism. It can only be managed through intensive intervention programmes including education, support and behavioral therapies – aiming to minimize symptoms and improve quality of life.
What role could vitamin D possibly play in autism? What are the possible mechanisms through which vitamin D supplements may help manage autism? We are going to talk about all this and more in our future blogs. Stay tuned.
- Khaled Saad et al. Randomized controlled trial of vitamin D supplementation in children with autism spectrum disorder. Journal of Child Psychology and Psychiatry. October 2016.
- Mc Grath et al. Gestational vitamin D deficiency and autism-related traits: the Generation R Study. Molecular Psychiatry. 29 November 2016
- Mackay et al. Month of Conception and Learning Disabilities: A Record-Linkage Study of 801,592 Children. Am J Epidemiol. 2016