Autism Spectrum Disorder (ASD) is a neurodevelopmental condition with increasing prevalence worldwide and no approved treatments for its core symptoms. This randomized, double-blind, placebo-controlled trial evaluated the effects of a probiotic mix (K11) and a formulation combining probiotics with vitamins, amino acids, and minerals (K11-TMAX) in children with ASD. 

A total of 505 children aged 3–11 years were initially enrolled in the study. After applying inclusion and exclusion criteria, 207 participants were selected and randomized into three groups: placebo, K11, and K11-TMAX. Assessments were conducted at baseline, 45 days, and 90 days. The study was completed with 182 participants. Among them, 4.3% discontinued due to family decisions, while 7.7% were excluded for failing to attend scheduled evaluations. 

Primary outcomes were measured using the Vineland Adaptive Behavior Scales (Vineland-3), while secondary outcomes included the Autism Diagnostic Observation Schedule (ADOS-2), Childhood Autism Rating Scale (CARS), and inflammatory biomarkers. 

After 90 days, both probiotic groups showed statistically significant improvements (p < 0.05) in Vineland-3 subdomains such as communication, daily living skills, motor skills, and adaptive behavior. The overall average improvement across these domains was 79.6%, highlighting the intervention’s meaningful impact on adaptive functioning. Additionally, the K11 group showed significant improvement in socialization. 

ADOS-2 and CARS assessments further supported the reduction in autism-related symptoms in the probiotic groups compared to the placebo at both 45 and 90 days. Notably, ADOS-2 results showed an average improvement of 138.2% across domains such as interpersonal relationships, emotional response, object use, auditory response, and intellectual response. These changes suggest a shift toward typical developmental profiles, reinforcing the therapeutic potential of probiotic treatment. 

Biochemical analyses revealed significant reductions in insulin, C-reactive protein, and cortisol levels in both K11 and K11-TMAX groups. Furthermore, fecal calprotectin levels decreased significantly in the K11-TMAX group. 

Microbiota analysis indicated a significant increase in Lactobacillus and a reduction in E. coli counts in the probiotic groups. Additionally, 81% of participants reported improvements in gastrointestinal symptoms, supporting the intervention’s positive impact on gut health. 

These findings suggest that K11 and K11-TMAX may alleviate core ASD symptoms, modulate gut inflammation, and influence microbiota composition, offering promising therapeutic benefits with minimal side effects. 

REC approval: CAAE #77402523.6.0000.5064; Opinion No. 6.715.143; ClinicalTrials.gov #NCT06382909. 

Keywords: Probiotics, Autism Spectrum Disorder, Gut-Brain Axis, Adaptive Behavior, Microbiota Modulation, Inflammatory Biomarkers.