Food and Behaviour Research

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Autism: Will vitamin D supplementation during pregnancy and early childhood reduce the recurrence rate of autism in newborn siblings?

Stubbs G, Henley K, Green J. (2016) Med Hypotheses 88 74-8 doi: 10.1016/j.mehy.2016.01.015. Epub 2016 Feb 2.

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Vitamin D deficiency is widespread in the world including the vulnerable group of pregnant women. Vitamin D deficiency during pregnancy is hypothesized to contribute to the cause of autism. Further, it is hypothesized that vitamin D supplementation during pregnancy and early childhood will reduce the recurrence rate of autism in newborn siblings.


To investigate the hypothesis an open label prospective study was performed prescribing vitamin D during pregnancy to mothers of children with autism at a dose of 5000IU/day. The newborn siblings were at high risk for the recurrence of autism. The newborn infants were also prescribed vitamin D, 1000IU/day to their third birthday. The newborn siblings were followed for three years and during that time, were assessed for autism on two separate occasions: at 18months and 36months of age. The results were compared to the reported recurrence rates in siblings of autistic children in the literature.


The final outcome was 1 out of 19 (5%) developed autism in contrast to the recurrence rate of approximately 20% in the literature. We did not have a control group, nor was there blinding.


The results are promising, however, this is a preliminary study with very small numbers and was uncontrolled. Further study with larger numbers is indicated. The ethics of prescribing a low dosage of vitamin D such as 400IU D3/day to a control group of mothers in comparison to a large dose such as 5000IU D3/day are problematic in our opinion.