A literature search found no well-documented evidence showing that implementing a gluten-and-casein-free diet in children with autism produces statistically significant differences in autism-related behaviors.
Giving children with autism a diet free of gluten and casein does little to treat the condition, say researchers who presented a critical analysis of several studies at the 2013 American College of Gastroenterology annual scientific meeting in San Diego.
The purpose of the review led by Nidhi Rawal, MD, of the University of Maryland, was to determine the safety and efficacy of eliminating gluten and casein from the diet of children with autism spectrum disorders.
“Our systematic review of scientific literature shows no evidence to support empirical use of gluten- and casein-free diets to improve autism-related behaviors,” Rawal said of the findings.
Rawal and her colleagues searched five medical databases from 1980 to 2013 for the words “autism” and “diet” and selected all peer-reviewed articles that reported on the effect of a gluten-and casein-free diet.
For each study, researchers looked at and evaluated design, interventions, outcome measures, results, and statistical significance, as well as who participated and whether a control group was included.
Researchers considered the evidence weak if no control group was used. A “positive outcome” was defined as statistically significant improvement in standardized scores after a gluten- and casein-free diet was introduced. A “negative outcome” was defined as either no improvement or improvement that was not statistically significant, or if there was no statistical analysis performed.
There were 29 studies out of 111 publications that were reviewed based on the inclusion criteria. Seventeen reported positive outcomes but of those only 6 met the review criteria for a “positive outcome study.” They included four observational studies and two randomized controlled trials.
“The quality was very low in these studies that were positive,” Rawal said.
The studies that had better designs had a negative outcome, noted Rawal. One double-blind, randomized controlled trial reported no statistically significant difference in autism-related behaviors after implementing a gluten-and casein-free diet.
The popularity of a gluten-and-casein-free diet was indicated by the literature review that showed a significant use as a way to manage autism in children. However, the researchers noted that when critically analyzed for methodological rigor, results showed no well-documented evidence for the efficacy of such a diet in children with autism spectrum disorders. The poor quality of scientific evidence included extreme variability in design among studies, inconsistent use of standardized behavior measuring tools, and control group challenges.
“The quality of study design varied significantly between the studies and hence it is not possible to arrive to any conclusion in terms of efficacy,” Rawal said.
The researchers suggested that gluten-and casein-free diets for the management of children with autism should be further investigated with large-scale, randomized controlled trials given the potential for nutritional deficiencies of restrictive diets.