Autism Spectrum Disorder, or ASD, is a complex developmental and neurological condition that affects brain function—particularly in social interaction and communication skills. ASD usually begins in early childhood with symptoms including speech delays, lack of interest in playing and interaction, and poor eye contact. According to the World Health Organization (WHO), one in 100 children has autism worldwide . In addition, the Centers for Disease Control and Prevention estimates that one in every 44 children in America has ASD. Although the causes of ASD are not well-known, genetics, environment, nutrition, and immunological factors are reported to play a role [2,3]. This article presents some of the major nutritional and dietary considerations being researched with regard to ASD.
Among nutritional and environmental factors, vitamin D3 (cholecalciferol) plays a notable role in biological activities like brain development, cellular proliferation, differentiation, calcium signaling, neurotrophic, and neuroprotective actions. . ASD is linked with decreased vitamin D levels in patients . Decreased maternal vitamin D levels during pregnancy are observed with ASD in many studies . Some studies with increasing vitamin D levels have shown improvement in core ASD symptoms, but further large-sample studies, including randomized, double-blind trials, are needed .
Vitamin B12 deficiencies can affect cell production and brain function, specifically developmental delays in speech and language in young children. Many studies have observed improvement in speech and language abilities after B12 intervention . While methyl B12 injections and B12 supplementation have grown in popularity as alternative treatments for autism, more studies are required to determine whether methyl B12 could be used as a dietary supplement for ASD .
Gastrointestinal disorders are known to be one of the most common medical conditions that are comorbid with ASD. Emerging research indicates a possible connection between autism and the imbalances in the composition of microbiota in the gut. Alterations within the microbiome-gut-brain (MGB) axis could play a role in the development of ASD . The MGB axis is a link between the gut and the brain that allows the brain to influence intestinal activities, including mood, cognition, and mental health. Therefore, gut microbiome modulation offers a promising approach to managing ASD. Prebiotics and probiotics offer a non-invasive, straightforward approach to addressing MGB dysfunction in children with ASD. While probiotics are the live culture of beneficial bacteria and yeast, prebiotics are the fibers that stimulate their growth, and together they can promote a healthy gut microbiome. .
In 2002, Paul Shattock proposed the Opioid Excess Theory, which hypothesizes that autism results from a metabolic disorder where opioid peptides pass through an abnormally permeable intestinal membrane and then affect neuro-transmission through binding with opioid receptors. These opioid peptides result from incomplete digestion of certain foods—especially gluten from wheat and other grains and casein from dairy . Elevated levels of opioid peptides have been observed in the urine of more than 70% of people with autism. These peptides are thought to leak out of the intestines into the bloodstream—making their way to the brain to attach to neuroreceptors and negatively impacting neurotransmission, resulting in behavioral problems and increased symptoms of ASD . Many investigations have attempted to determine the effectiveness of gluten and casein-free diets for treating ASD. For example, a study conducted by Knivsberg and colleagues showed a significant decrease in autistic traits in the combined gluten and casein-free diet group versus those in the regular diet group . However, the sample sizes and the quality of studies have not yielded statistically significant results.
Today, around 80% of parents with autistic children report to be using some dietary intervention. However, the American Academy of Pediatrics does not endorse alternative diets to treat autism. Alternative diets and supplements pose a considerable risk because they can mask underlying medical conditions or lead to nutritional deficiencies, increased stress, and financial burden for families. Any restrictive diet and supplements require careful planning with the child’s physician to rule out underlying medical conditions and guidance on safe supplements and probiotics as needed . Physicians may refer the child to a registered dietitian nutritionist, who can work with the child to identify any nutritional risks, discuss the effectiveness and safety of nutrition therapies and supplements, and help create a meal plan for healthful living.
World Health Organization. (2022, March 30). Autism. World Health Organization. Retrieved October 28, 2022, from https://www.who.int/news-room/fact-sheets/detail/autism-spectrum-disorders.
Ranjan S, Nasser JA. Nutritional Status of Individuals with Autism Spectrum Disorders: Do We Know Enough? Adv Nutr. 2015;6:397–407. doi: 10.3945/an.114.007914.
Esparham AE, Smith T, Belmont JM, et al. Nutritional and metabolic biomarkers in autism spectrum disorders: An exploratory study. Integr Med. 2015;14:40–53.
Cannell JJ. Vitamin D and autism, what’s new? Rev Endocr Metab Disord (2017) 18(2):183–93. 10.1007/s11154-017-9409-0. https://pubmed.ncbi.nlm.nih.gov/28217829.
Wang T, Shan L, Du L, Feng J, Xu Z, Staal WG, et al. Serum concentration of 25-hydroxyvitamin D in autism spectrum disorder: a systematic review and meta-analysis. Eur Child Adolesc Psychiatry (2016) 25(4):341–50. 10.1007/s00787-015-0786-1 https://pubmed.ncbi.nlm.nih.gov/26514973.
Grant WB, Soles CM. Epidemiologic evidence for supporting the role of maternal vitamin D deficiency as a risk factor for the development of infantile autism. Dermatoendocrinol (2009) 1(4):223–8. 10.4161/derm.1.4.9500. https://pubmed.ncbi.nlm.nih.gov/20592795.
Wang, J., Huang, H., Liu, C., Zhang, Y., Wang, W., Zou, Z., Yang, L., He, X., Wu, J., Ma, J., & Liu, Y. (2022). Research Progress on the Role of Vitamin D in Autism Spectrum Disorder. Frontiers in behavioral neuroscience, 16, 859151. https://doi.org/10.3389/fnbeh.2022.859151
James SJ, Cutler P, Melnyk S, Jernigan S, Janak L, Gaylor DW, et al. Metabolic biomarkers of increased oxidative stress and impaired methylation capacity in children with autism. Am J Clin Nutr (2004) 80(6):1611–7. https://pubmed.ncbi.nlm.nih.gov/15585776.
Is there a connection between vitamin B12 and autism? Simple Spectrum Supplement. (2022, February 15). Retrieved November 12, 2022, from https://simplespectrumsupplement.com/blogs/news/is-there-a-connection-between-vitamin-b12-and-autism
Coretti L, Paparo L, Riccio MP, Amato F, Cuomo M, Natale A, et al. Gut microbiota features in young children with autism spectrum disorders. Front Microbiol. 2018;9:3146. https://doi.org/10.3389%2Ffmicb.2018.03146
Abdellatif, B., McVeigh, C., Bendriss, G., & Chaari, A. (2020). The Promising Role of Probiotics in Managing the Altered Gut in Autism Spectrum Disorders. International journal of molecular sciences, 21(11), 4159. https://doi.org/10.3390/ijms21114159.
Shattock P, Whiteley P (2002) Biochemical aspects in autism spectrum disorders: updating the opioid-excess theory and presenting new opportunities for biomedical intervention. Expert Opin Ther Targets 6: 175-183. https://www.ncbi.nlm.nih.gov/pubmed/12223079.
Knivsberg AM, Reichelt KL, Høien T, Nødland M (2002) A randomised, controlled study of dietary intervention in autistic syndromes. Nutr Neurosci 5: 251-261. http://www.ncbi.nlm.nih.gov/pubmed/12168688
Ansel, C. K. (2022, April 1). Autism spectrum disorders and Diet. EatRight. Retrieved October 28, 2022, from https://www.eatright.org/health/diseases-and-conditions/autism/nutrition-for-your-child-with-autism-spectrum-disorder-asd.