There is evidence that some individuals on the autism spectrum may have nutritional and metabolic problems. For example, some autistic people eat restricted diets which are nutritionally imbalanced and can lead to severe nutrition deficiencies. Symptoms of severe deficiencies include skin rashes, mouth sores, limps, unexplained irritability, eyesight changes and severe ill health. The effects of these can be life threatening and life changing. There is also evidence that some individuals on the autism spectrum may have other nutritional and metabolic problems that have less severe, but behaviourally or medically significant effects.
However, the number of individuals on the autism spectrum who have these problems is not clear. It is also not clear whether these problems or differences are any more common in individuals on the autism spectrum than in other individuals. Possibly, these problems cause or worsen symptoms (of autism or related issues). Or maybe they arise because of autism, or they could be completely unrelated to autism. Nobody knows.
Most dietary supplements provide the same benefits for people on the autism spectrum as they do to people who are not on the autism spectrum. They do not appear to provide any additional benefits to people on the autism spectrum, according to a limited amount of research evidence of sufficiently high quality. Some dietary supplements may make some problems worse for some children and young people on the autism spectrum according to a limited amount of research evidence of sufficiently high quality. There is no high quality research to suggest that any dietary supplements provide any benefits to adults on the autism spectrum.
For details of the research on specific supplements, where it exists, please see http://researchautism.net/vitamins-and-minerals and http://researchautism.net/other-dietary-supplements.
The National Institute for Health and Care Excellence (NICE) is a UK government body which supports healthcare professionals and others to make sure that the care they provide is of the best possible quality and offers the best value for money.
NICE made the following observations on the use of dietary supplements for adults on the autism spectrum. “... there is very little evidence regarding safety and efficacy for exclusion diets, vitamins, minerals or supplements for the treatment of autism. Moreover, it is important to bear in mind that ... some dietary supplements can be associated with adverse side effects and/or interact and perhaps interfere with the action of other supplements or prescribed drugs”. (NICE, 2012)
NICE also reported that some dietary supplements may be beneficial for some children and young people on the autism spectrum. However it also reported that “... the evidence was very limited and further randomised placebo-controlled studies are required to corroborate the existing evidence for ... dietary supplements in children and young people with autism”. (NICE, 2013).