Dietary interventions for autism spectrum disorder: An updated systematic review of human studies

Abstract

Autism is a complex spectrum of disorders (ASD) with genetic, epigenetic, autoimmune, oxidative stress, and environmental aetiologies. Treatment of ASD using dietary approaches is a promising strategy, especially owing to its safety and availability. Our study critically analysed the roles and efficacy of antioxidants, probiotics, prebiotics, camel milk and vitamin D. This systematic review provides an updated synopsis of human studies that investigated therapeutic benefits of these dietary interventions in autism. A total of 943 papers were identified out of which 21 articles were included in the systematic review. The selected studies investigated the impact of 5 different dietary supplementations in ASD symptoms and behaviours. These agents include; antioxidants/polyphenolic compounds, probiotics, prebiotics, camel milk and vitamin D. From the results of the present review, antioxidants/polyphenolic compounds decreased the levels of inflammatory cytokines and improved behavioural symptoms. Probiotics improved behavioural and GI symptoms as well as restored gut microbiota equilibrium. Prebiotics decreased levels of inflammatory cytokines, improved behavioural and GI symptoms and improved gut microbiota. Vitamin D improved behavioural symptoms and offered protective effects against neurotoxicity. Camel milk reduced inflammatory responses and oxidative stress. Given the chronic nature as well as early onset of ASD, dietary supplements become useful to complement nutritional deficiencies in children with ASD. Key benefits of these agents stem from their ability to target multiple physiological areas via the gut brain-axis while they are devoid of potential harmful or aggravating effects on ASD patients. The evidence collated in this review propose that dietary intervention may provide a new platform for the management of autism.

The gut microbiome in children with mood, anxiety, and neurodevelopmental disorders: An umbrella review

“…The impact of prebiotic, probiotic, and synbiotic supplementation on Bifidobacterium in the gut was inconsistent. Some studies (Yang et al, 2020; Mitchell and Davies, 2021; Prosperi et al, 2022) reported an increase in Bifidobacterium levels, while others reported decreased levels (Lasheras et al, 2021; Amadi et al, 2022).…”

The connection between epigenetics and gut microbiota‐current perspective

“…The ketogenic diet also has effects on epigenetic mechanisms 56 . The gut metabolites of some phytoestrogens can act as epigenetic modulators for improved human health 57 . An improved behavioral symptoms was observed by both vitamin D initiated by antioxidants and polyphenolic compounds.…”

“…56 The gut metabolites of some phytoestrogens can act as epigenetic modulators for improved human health. 57 An improved behavioral symptoms was observed by both vitamin D initiated by antioxidants and polyphenolic compounds. While decreased inflammatory cytokines were seen with the latter, neurotoxicity was conferred against the former.…”

The Role of Vitamin D in Stroke Prevention and the Effects of Its Supplementation for Post-Stroke Rehabilitation: A Narrative Review

“…The effect of vitamin D on the intestinal microflora was also confirmed in a pilot clinical study by Charoenngam et al Similar to Singh, they investigated the gut microbiome following an intervention with oral vitamin D (600, 4000 and 10,000 IU/day) in adults deficient in vitamin D. They observed a dose-dependent reduction in inflammatory bowel disease associated with an increase in commensal bacteria while reducing the amount of pathogens [107]. Altering the diversity of the gut microflora with vitamin D supplementation has also been studied in many diseases, including cystic fibrosis [108], multiple sclerosis [109], autism/autism spectrum disorder [110,111], diabetes, and obesity [112]. Kanhere et al assessed the effect of a 12-week intervention with high doses of vitamin D (50,000 IU/week) on the composition of the intestinal and respiratory microflora in patients with cystic fibrosis with vitamin D deficiency.…”

“…Similar findings were presented by Cantarel et al, who assessed vitamin D supplementation (5000 IU/day for 90 days) on the intestinal microflora in multiple sclerosis. They also noted a shift in the composition of the intestinal microflora in favor of commensal bacteria [110]. Finally, Hussein et al investigated the effect of vitamin D (500 IU/kg/day) on the colon cannabinoid 1 receptor (CB1R), which directly connects the gut microflora to metabolic and cognitive disorders, compared to metformin (200 mg/kg/day) in rats.…”