Autism spectrum disorders (ASD) are increasingly prevalent developmental disorders that affect children by impairing their ability to communicate verbally and nonverbally and to interact socially. There is currently no cure for ASD. However, early intervention treatments have been shown to improve children’s development by helping them learn important skills.

Several genetic factors are known to influence the etiology of ASD, but these do not apply to the majority of autistic patients. The importance of environmental factors in the development of ASD has been gaining ground, namely the contribution of autoimmunity, early exposure to viruses and drugs, and altered gastrointestinal bacterial composition. In fact, studies have shown that 70% of children with ASD report gastrointestinal complaints that strongly correlate with the severity of autism and that include changes in nutrient absorption, altered  digestion, microbial overgrowth and abnormal intestinal permeability.

Consequently, an alternative therapy that has recently been gaining popularity is the use of specialized diets to reduce autism symptoms, either through the use of nutraceuticals or through restriction diets. This stems from theories that link ASD with metabolic disorders, allergy or high sensitivity to certain foods.

By counterbalancing these deficits, specialized diets could indeed offer several promising health benefits. If its efficacy is indeed validated, dietary restrictions and the use of nutraceuticals in ASD therapy could potentially be an easy approach to the management of its symptoms. Although research on nutritional therapies for autism is not abundant, there are some findings worth mentioning.

The gluten-free/casein-free diet, also known as the GFCF diet, has shown an increased popularity in ASD treatment. In this diet, all foods containing gluten (found in wheat, barley and rye) and casein (found in milk and dairy products) are removed from the daily food intake. This is based on a theory that states that children with autism may have an allergy or high sensitivity to foods containing gluten or casein, since elevated urine levels of gliadin and glutenin, the two main groups of proteins in gluten, and of casein peptides can be found in ASD patients. This can lead to an imbalance in the microbiota of the digestive tract leading to inflammation and to neurophysiological alterations via the brain-gut axis. 

An additional theory states that the peptides derived from incomplete breakdown of gluten and casein may have direct opioid action or act as ligands to the enzymes that would break down the endogenous opioids. However, there is not enough evidence to unequivocally support this hypothesis.

The goal of using the GFCF diet is to reduce symptoms that, in theory, are exacerbated by the different processing of gluten and casein. Indeed, symptom improvements have been reported, specifically in verbal and non-verbal communication, attention, aggressiveness, affection, motor skills, sleep, anxiety, empathy and learning. Moreover, reintroduction of gluten in the diet led to the worsening of symptoms such as hyperactivity and impulsivity, stereotyped behaviors, aggression and language and communication skills.

However, it is important to underline that, although improvements in autism symptoms due to this dietary approach have been described, the available experimental and clinical data is still insufficient to confidently affirm its efficacy.

Given the similarity between the symptoms of inflammatory bowel disease and irritable bowel syndrome and the gastrointestinal symptoms of ASD patients, a possible treatment of autism with probiotics has also been suggested. Studies using different probiotics have shown some beneficial effects such improved behavior outcomes, communication, and ability to concentrate and carry out orders. But again, evidence is still too scarce.

A positive role of vitamin and mineral-based nutraceuticals in treating ASD has also been described by some studies. One of these studies compared the effect of micronutrient supplementation with vitamins, dietary minerals, amino acids, and antioxidants (without any medication for autism) with the effect of conventional medication without supplementation. Results showed that although patients in both groups showed improvements, these were significantly greater in the dietary supplementation group.

Although there is compelling evidence supporting the presence of gastrointestinal alterations in ASD patients and a role for the brain-gut axis in the etiology of autism, the efficacy of nutritional interventions is still mostly speculative and in need of further research.

References

de Theije CG, Bavelaar BM, Lopes da Silva S, Korte SM, Olivier B, Garssen J, & Kraneveld AD (2014). Food allergy and food-based therapies in neurodevelopmental disorders. Pediatric allergy and immunology : official publication of the European Society of Pediatric Allergy and Immunology, 25 (3), 218-26 PMID: 24236934

Herbert MR, & Buckley JA (2013). Autism and dietary therapy: case report and review of the literature. Journal of child neurology, 28 (8), 975-82 PMID: 23666039

Marí-Bauset S, Zazpe I, Mari-Sanchis A, Llopis-González A, & Morales-Suárez-Varela M (2014). Evidence of the gluten-free and casein-free diet in autism spectrum disorders: a systematic review. Journal of child neurology, 29 (12), 1718-27 PMID: 24789114

Mehl-Madrona L, Leung B, Kennedy C, Paul S, & Kaplan BJ (2010). Micronutrients versus standard medication management in autism: a naturalistic case-control study. Journal of child and adolescent psychopharmacology, 20 (2), 95-103 PMID: 20415604

Sutcliffe JS (2008). Genetics. Insights into the pathogenesis of autism. Science (New York, N.Y.), 321 (5886), 208-9 PMID: 18621658

van De Sande MM, van Buul VJ, & Brouns FJ (2014). Autism and nutrition: the role of the gut-brain axis. Nutrition research reviews, 27 (2), 199-214 PMID: 25004237

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