vitamin D and autism

In a recent Irish study, researchers investigated whether there is a link between a deficiency in Vitamin D and autism in children.


Autism Spectrum Disorder (ASD) is a neurological condition with a diverse set of symptoms. Individuals with ASD are typically more sensitive to light and sound, display repetitive behaviours, and have a narrow range of interests. To varying degrees, they may also have impaired motor skills, verbal or nonverbal communicative ability, or social skills, and may think and learn differently than their peers. ASD is thought to be caused and contributed by a number of genetic and environmental risk factors.

Vitamin D, which plays roles in neurological development and function, has emerged as a potential risk factor. Research into the dietary habits of children with ASD has found them to have much lower Vitamin D intake than their peers and a few small studies have found that an increase in Vitamin D consumption may improve ASD symptoms. To establish whether there is a link between Vitamin D and autism, however, the effects of Vitamin D on ASD symptoms must be explored in depth.

What is the Effect of Vitamin D Supplementation?

In a recent Irish trial published in the Archives of Disease in Childhood, researchers investigated the effects of Vitamin D supplementation in children with ASD. Children with clinically-diagnosed ASD were recruited for the study. Those without a Social Communication Questionnaire score of 15 or greater, who were receiving Vitamin A supplements, or who had chronic health conditions were excluded. Participants were assigned to receive either Vitamin D or a placebo in the form of drops to be added to food. At the beginning of the trial, parents and guardians were given eight bottles of either Vitamin D or a visually identical placebo and instructed to administer 20 drops (2000 IU) per day for 20 weeks.

They assessed compliance based on diary entries provided by the parents and the number of bottles returned. Changes in symptoms were evaluated based on three measures: the Aberrant Behaviour Checklist (ABC), which assesses irritability, social withdrawal, typical behaviour, hyperactivity, and inappropriate speech; the Social Responsiveness Scale, which assesses social impairment; and the Developmental Disabilities-Children’s Global Assessment Scale (DD-CGAS), which assesses self-care, communication, social behaviour, and academic performance. Blood samples were taken before and after the trial to assess changes in Vitamin D levels.

Vitamin D Supplementation Had No Effect

A total of 42 children with ASD entered into the study, 38 of whom completed the trial. Compliance was high among participants. Of those who completed the trial, 20 had been assigned to the placebo group and 18 to the Vitamin D group. About 40% were Vitamin D-deficient at the start of the trial. By the end of the trial, Vitamin D levels were 28.7 nmol/L higher in the Vitamin D group than in the placebo group.

Although at the beginning of the trial there was a significant association between Vitamin D levels and hyperactivity, no association was found after having received Vitamin D or placebo supplementation. Individuals in the Vitamin D group scored 12.8 points (out of 100) higher on average than those in the placebo group on the self-care portion of the DD-CGAS, and those in the placebo group scored 2.4 points (out of 12) lower than in the Vitamin D group on the inappropriate speech section of the ABC. Overall, Vitamin D supplementation was not found to improve ASD symptoms compared to placebo.

The findings suggest that Vitamin D supplementation at 2000 IU/day provides no significant improvement in ASD symptoms. Introducing more stringent measures of compliance (e.g. dietary guidelines to reduce any undocumented Vitamin D intake) and dosing based on pre-trial Vitamin D levels or body weight instead of a standard supplement could have allowed the researchers to examine the effects of Vitamin D supplementation on each child more precisely. An investigation of its effects at higher doses and in large study populations grouped by Vitamin D status might provide more definitive results regarding the link, if any, between Vitamin D and autism.

Written by Raishard Haynes, MBS

Reference: Kerley, C.P. et al. (2017). Lack of effect of vitamin D3 supplementation in autism: a 20-week, placebo-controlled RCT. Arch Dis Child doi:10.1136/archdischild-2017-312783

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