There is some limited evidence to suggest that certain individuals on the autism spectrum may have a deficiency of vitamin B6. However, the number of individuals on the autism spectrum who have a vitamin B6 deficiency is not clear. It is also unknown whether a vitamin B6 deficiency can cause or worsen symptoms (of autism or related issues) or arises because of autism or is completely unrelated to autism.
There is a reasonable amount of low-quality research (11 group studies and two single-case design studies with three or more participants) into the use of vitamin B6 and magnesium supplements as an intervention for individuals on the autism spectrum.
However, because the quality of that research is so poor, we cannot determine whether vitamin B6 and magnesium are likely to provide any benefits to anyone on the autism spectrum. We must wait for further research of sufficiently high quality to be completed.
There is a need for further research into the use of vitamin B6 and magnesium supplements for people on the autism spectrum. Specifically, there is a need for studies which use robust methodology, for example, large-scale, placebo-controlled, randomised, double-blind trials carried out on several sites.
That research should also identify which individuals are most likely to benefit from which formulations and dosages; should determine if vitamin B6 and magnesium supplements can be used as one of the elements within comprehensive, multi-component, treatment models; should compare vitamin B6 and magnesium supplements with other interventions which are designed to achieve similar results, such as special diets.
That research should also identify if vitamin B6 and magnesium supplements have any beneficial or harmful effects in the medium to long term. It should also involve people on the autism spectrum in the design, development and evaluation of those studies.