Psychobiotics in pediatric autism spectrum disorder: A systematic review of efficacy, mechanisms, and clinical translation

Table 7 Characteristics of included prebiotic studies in children with autism spectrum disorder

Ref.	Study design	Sample characteristics	Prebiotic type	Dose	Duration	Microbiome outcomes	Clinical outcomes
Grimaldi et al[36], 2018	Dietary intervention study	30 children with ASD	B-GOS	1.8 g (80% GOS content)	6 weeks	Increased Lachnospiraceae; altered fecal and urinary metabolites	Improvement in anti-social behavior
Palmer et al[37], 2025	Double-blind randomized placebo-controlled trial	33 children with ASD (4-10 years)	GOS	2.4 g/day	6 weeks	Threefold increase in Bifidobacterium (1.4%-5.9%, P < 0.001)	No significant behavioural differences vs placebo; moderate improvement in GI symptoms (effect size d = 0.47)
Raghavan et al[38], 2022	Randomized parallel-group pilot study	18 children with ASD	β-glucan (Nichi Glucan)	0.5 g twice daily	90 days	Not evaluated	Significant reduction in CARS scores (P = 0.034); increased plasma α-synuclein levels
Inoue et al[39], 2019	Clinical dietary supplementation study	Children with ASD and constipation	PHGG	6 g/day	2-15 (median = 2 months)	Altered gut microbiota composition	Increased defecation frequency, reduced IL-1β and TNF-α, decreased behavioral irritability
Saxami et al[40], 2023	In vitro microbiome fermentation study	Fecal samples from autistic and neurotypical children	Mushroom-derived prebiotics (Pleurotus eryngii, Pleurotus ostreatus)	Not applicable	24-hour fermentation model	Increased Bifidobacterium, Bacteroides, and Faecalibacterium prausnitzii; increased butyrate production	Mechanistic study (no direct clinical outcomes)
Grimaldi et al[41], 2017	In vitro gut model study	ASD and neurotypical fecal microbiota	B-GOS prebiotic	Not applicable	Gut model simulation	Increased Bifidobacterium and Lactobacillus; altered SCFA production	Mechanistic microbiome outcomes only

ASD: Autism spectrum disorder; B-GOS: Bimuno^® galacto-oligosaccharide; GOS: Galacto-oligosaccharides; IL-1β: Interleukin-1 beta; PHGG: Partially hydrolyzed guar gum; SCFAs: Short-chain fatty acids; TNF-α: Tumor necrosis factor alpha.