Nutritional management and autism spectrum disorder: A systematic review

Table 3 The dietary interventions, supplements, and their related details for autism spectrum disorder

Intervention/supplement	Description	Functions	Potential links with ASD	Current research findings	Practical considerations
Gluten-free diet	Eliminates gluten (wheat, barley, rye). Requires careful planning for nutritional adequacy	Aims to improve gastrointestinal symptoms, behavior, attention, and social interactions	Increased sensitivity to gluten may affect brain function	Mixed evidence; more rigorous trials are needed.	Strict adherence is challenging; potential nutritional deficiencies; more expensive and less accessible
Casein-free diet	Eliminates casein (dairy products). Requires careful planning for nutritional adequacy	Aims to improve gastrointestinal symptoms, behavior, attention, and social interactions	Sensitivity or allergy to casein may exacerbate autism symptoms	Mixed evidence; more rigorous trials are needed	Strict adherence is challenging; potential nutritional deficiencies; more expensive and less accessible
Ketogenic diet	High-fat, low-carbohydrate, moderate-protein diet. Requires careful planning, medical evaluation, and regular monitoring	Aims to improve behavior, cognitive function, seizure control, and gastrointestinal symptoms	Ketones may have neuroprotective properties and improve brain function	Limited data; more rigorous trials are needed.	Potential nutritional deficiencies; strict adherence is challenging; potential side effects (GI discomfort, kidney stones, increased cholesterol)
Specific carbohydrate diet	Eliminates complex carbohydrates, disaccharides, and polysaccharides. Includes meats, certain vegetables, fruits, nuts, and seeds	Aims to improve gastrointestinal symptoms, behavior, and cognitive function	Addresses gut dysbiosis and gastrointestinal inflammation	Mixed results; more rigorous trials are needed	Restrictive; potential nutritional deficiencies; strict adherence is challenging; more expensive and less accessible
Gut and psychology syndrome diet	Structured in phases, includes bone broths, fermented foods, and healthy fats	Aims to improve gut health, behavior, cognitive function, and overall well-being	Focuses on healing the gut lining and restoring healthy gut flora	Limited peer-reviewed research; indirect support from studies on gut microbiota.	Restrictive; potential nutritional deficiencies; challenging to implement; anecdotal evidence
Camel milk	Rich in vitamins, minerals, and unique proteins	Anti-inflammatory, antioxidant, immune modulation, gut health promotion	Emerging research suggests behavioral improvements, cognitive functions, and GI symptom relief	Emerging research and anecdotal reports suggest significant benefits	Obtain from reputable sources, gradually introduce, consult healthcare provider for dosage, monitor response and allergic reactions
Probiotics	Restores healthy gut bacteria balance, reduces gut inflammation, strengthens gut barrier	Improves GI function, potential behavioral improvements	May improve gut health and behavior by restoring healthy gut bacteria	Mixed results; some studies show improved GI and behavioral symptoms	Choose effective strains, determine optimal dosage with clinical guidance, monitor and adjust based on individual response
Prebiotics	Promotes growth of beneficial gut bacteria, reduces inflammation, supports neurotransmitter synthesis	Improves gut health, potential behavioral and cognitive benefits	May improve gut health and behavior by promoting beneficial gut bacteria growth	Limited human trials but promising; animal models support positive effects	Start with low dose, include prebiotic-rich foods, use supplements under healthcare guidance, consider combining with probiotics, monitor for adverse reactions
High-dose methylcobalamin	Supports methylation cycle, boosts glutathione synthesis, neuroprotective properties	Enhances cognitive functions, reduces oxidative stress, improves detoxification	May improve behavioral and cognitive functions, reduce oxidative stress	Promising results; improved methylation capacity and reduced oxidative stress markers	Administer via injections, determine dosage with healthcare provider, regular monitoring of vitamin B12 Levels, consider combined treatment with folinic acid
Folic acid	Supports DNA methylation, reduces homocysteine levels, involved in neurotransmitter synthesis	Potential reduction in ASD risk, improved neurodevelopment, reduced oxidative stress	Prenatal supplementation may reduce ASD risk.	Prenatal doses support reduced ASD risk; large epidemiological studies support benefits	Recommend 400-800 mcg/day prenatal doses, consider genetic variations, ensure balanced diet, consult healthcare provider for high doses
Vitamin B6	Synthesizes neurotransmitters, reduces homocysteine levels, converts glutamate to GABA	Potential improvements in behavior, language development, cognitive function	May improve behavior, language, and cognitive functions	Mixed results; some studies show improvements; variability in outcomes	Determine dosage with healthcare provider, monitor for side effects (peripheral neuropathy), consider combination with magnesium.
Vitamin D	Fat-soluble vitamin; exists as vitamin D2 and D3; synthesized in skin or obtained from food sources	Facilitates calcium and phosphorus absorption, modulates immune system, reduces inflammation, supports brain development	Low vitamin D levels linked with ASD risk; deficiency associated with immune dysregulation and neurotransmitter imbalances	Benefits of vitamin D3 supplementation include improved autism severity scores and social behaviors	Dosage varies; general recommendation 600-800 IU daily; excessive intake can lead to toxicity; regular monitoring essential
L-Carnitine	Naturally occurring amino acid derivative; involved in energy metabolism and mitochondrial health	Facilitates fatty acid transport into mitochondria, supports mitochondrial health, and has antioxidant properties	Mitochondrial dysfunction and oxidative stress observed in autism; L-carnitine may improve mitochondrial function and reduce oxidative stress	Lower L-carnitine levels in autism; improvements in behavior and communication with supplementation.	Dosage ranges from 50 to 100 mg/kg/day; consult healthcare providers; generally safe but may cause gastrointestinal discomfort or fishy odor
Omega-3 and Omega-6	Essential polyunsaturated fatty acids; Omega-3 (ALA, EPA, DHA) and Omega-6 (LA, AA)	Vital for brain function, anti-inflammatory effects, and overall neural health	Omega-3 deficiencies may impair neurodevelopment; Omega-3s may improve behavior; Omega-6 imbalance can promote inflammation	Mixed results; some studies show improvements in behavior, cognitive development, and social skills	No standardized dosage; consult healthcare providers; high doses may cause GI issues and increased bleeding risk; balance omega-3 and omega-6 intake

ASD: Autism spectrum disorder; ALA: Alpha-linolenic acid; EPA: Eicosapentaenoic acid; DHA: Docosahexaenoic acid; LA: Linoleic acid; AA: Arachidonic acid; GI: Gastrointestinal; GABA: gamma-aminobutyric acid.