1. A meta-analysis of studies evaluating dietary interventions used in treatment of autism spectrum disorder (ASD) in children found that omega-3, vitamin supplementation, and other supplementations were more effective than placebo in treating a number of ASD symptoms.
2. All types of dietary interventions had small effect sizes relative to placebo, as well as low statistical heterogeneity and low risk of publication bias.
Evidence Rating Level: 1 (Excellent)
Study Rundown: Dietary and nutritional interventions are used by many families to treat ASD. However, evidence for the efficacy of most of these interventions remains limited and controversial. In this meta-analysis, researchers used study-level data from 27 randomized clinical trials studies to examine the effect of dietary intervention on an array of symptom groups in subjects with ASD. The meta-analysis revealed that dietary supplementation, including omega-3 and vitamin supplementation, was significantly more effective than placebo in treating a number of clinical domains, including anxiety, behavioral problems and impulsivity, and restricted and repetitive behaviors. These relationships were all of small effect sizes relative to placebo.
These findings are limited by the methodologic heterogeneity of the studies, which varied in intervention dose, outcome measures, follow-up time, and sample characteristics. Furthermore, most of the included studies did not assess the presence of baseline nutritional deficits. Nonetheless, the study is strengthened by its extensive meta-analysis of a large aggregated sample. For physicians, these findings suggest that there is little evidence to support the use of nonspecific dietary interventions in children with ASD, although there may be some benefits from a number of specific dietary interventions.
In-Depth [meta-analysis]: Researchers used publication databases to identify 2283 records of placebo-controlled, double-blind, randomized clinical trials published from database inception to September 2017 that examined the effectiveness of dietary interventions on 17 symptom groups relating to ASD. Studies were included if they were published in English, had at least 5 subjects in the ASD intervention group, and included individuals diagnosed with ASD, pervasive development disorder, or Asperger syndrome. They conducted a meta-analysis using study-level data from 27 studies, comprising a total sample of 1028 subjects with ASD, to calculate Hedges’ adjusted g values* as estimates of effect size of dietary intervention relative to placebo.
Meta-analyses revealed that dietary supplementation (omega-3, vitamin supplementation, and/or other supplementation) was more effective than placebo in treating a number of clinical domains and symptoms, including anxiety (Hedges’ g = 0.482, 95% confidence interval [CI] 0.167-0.797), behavioral problems and impulsivity (Hedges’ g = 0.482, 95%CI 0.242-0.721), and restricted and repetitive behaviors (Hedges’ g = 0.269, 95%CI 0.106-0.432). All types of dietary intervention had small effect sizes relative to placebo, as well as low statistical heterogeneity and low risk of publication bias.
*Hedges’ g is a measure of effect size that incorporates the difference in means between groups and the pooled and weighted standard deviation. A g of 1 indicates the 2 groups differ by 1 standard deviation.
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