One challenge is that many autistic children have a strong need for consistent routine or "sameness," Dawson said, which can cause anxiety when asked to try new foods. Children with autism can also have sensory sensitivities, causing aversions to certain textures or tastes.
Some autistic children have motor delays that can cause problems eating or swallowing.
And although the underlying causes are poorly understood, autism is also associated with gastrointestinal problems, such as constipation and diarrhea, leading some kids to avoid eating.
In the study, some 8 percent of parents reported that their children were on a special "allergy" diet, compared to about 2 percent of other kids. Though there was no other information collected about what the allergy might be, many parents put their children on diets free of gluten (wheat) and casein (dairy). There is little evidence it helps ease symptoms, according to recent studies.
One strength of the findings, Dawson said, is that parents were queried about their children's diets prior to an autism diagnosis, reducing the chances of bias in describing their child's behavior. The median age of diagnosis was just under 4 years.
"The eating difficulties appear to start very early and seem to be pretty inherent in the syndrome for many kids," Dawson said.
Dawson agreed with the researchers' suggestion that children who have persistent feeding difficulties may need to be screened for autism.
The U.S. National Institute of Neurological Disorders and Stroke has more on autism.
SOURCES: Pauline Emmett, Ph.D., nutritionist, University of Bristol, Bristol, England; Geraldine Dawson, Ph.D., chief science officer, Autism Speaks, New York, N.Y.; Pediatrics, August 2010
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