Effect of diet intervention on symptoms in autism spectrum disorder: An umbrella review

The study systematically evaluated the efficacy of dietary interventions in improving clinical symptoms of ASD through umbrella review methodology. A total of 15 meta-analyses were included, covering 118 clinical studies with a total of 5033 ASD patients, with an age range of 1.5-45 years for individuals with ASD. Primary interventions included gluten-free and casein-free (GFCF) diets, probiotics, Vitamin D, and polyunsaturated fatty acids (PUFAs). We found that dietary interventions significantly improved overall symptoms (SMD = -0.26, 95% CI [-0.33, -0.18]), communication (SMD = -0.16, 95% CI [-0.30, -0.01]), social interaction (SMD = -0.18, 95% CI [-0.33, -0.02]), and hyperactivity (SMD = -0.20, 95% CI [-0.39, -0.02]). Vitamin D showed the most significant effect on overall symptoms of ASD (SMD = -0.45). However, dietary intervention did not show significant improvement in four outcomes: stereotypical behaviour, irritability, lethargy, and inappropriate speech. Future large-scale multicentre RCTs are needed to explore the neurobiological mechanisms and safety of dietary intervention, with a focus on monitoring changes in objective indicators such as gut microbiota and blood biochemical markers.