A gluten and casein-free diet may lead to improvements in behaviour and physiological symptoms in children with autism spectrum disorder (ASD), recent research has suggested.

Researchers from Penn State College of Medicine discovered that autistic children with gastrointestinal (GI) symptoms, who follow a gluten and casein-free (the protein found in milk), experienced an improvement in behaviour and ASD symptoms.

The research team questioned 387 parents of children with ASD and asked them about their child’s GI symptoms, food allergies, suspected food allergies and diet.

Researchers discovered that GI symptoms improved in those with ASD who followed a strict gluten and casein-free diet. Other symptoms linked to ASD, like social behaviour (eye contact, engagement, attention span, social responsiveness) also improved.

The results were compared to autistic children without GI symptoms and those whose parents did not restrict their gluten and casein intake.

“Research has shown that children with ASD commonly have GI symptoms. Notably, a greater proportion of our study population reported GI and allergy symptoms than what is seen in the general paediatric population,” Christine Pennesi, from the study said in a statement.

“Some experts have suggested that gluten- and casein-derived peptides cause an immune response in children with ASD, and others have proposed that the peptides could trigger GI symptoms and behavioural problems."

However, researchers added that parent’s who implemented the diet on their child for six months or less, reported the diet as less effective in reducing their child’s ASD symptoms.

This also applied to parents who chose to only eliminate either gluten or casein from their child’s diet, instead of both.

Despite these positive findings, researchers admitted that more research needed to be done.

“While more rigorous research is needed, our findings suggest that a gluten-free, casein-free diet might be beneficial for some children on the autism spectrum,” explains Pennesi. “It is possible that there are other proteins, such as soy, that are problematic for these children.”

Caroline Hattersely, head of information, advice and advocacy at The National Autistic Society, agrees that more research needs to be done.

“Although some individuals and parents of children with autism report benefits from following special diets, we would still urge caution over this study as there simply has not been enough scientific research investigating the link between autism and food intolerances,” Hattersely told The Huffington Post.

“It can be very difficult to follow gluten-free or casein-free diets strictly, and dietary restrictions can lead to poor nutrition, so they should only be carried out following advice from a medical professional.”

Virginia Bovell from the Ambitious About Autism charity is also mother to an autistic teenager who follows a gluten-free diet. She told The Huffington Post:

“The Ambitious About Autism welcomes research in this area as many parents are interested in this type of intervention but are worried about the lack of supported evidence.

“However, we agree that much more research is needed as only a proportion of children with ASD suffer from underlying gastrointestinal problems. Therefore, the impact of changing your child’s diet may not be the same for every autistic child. There isn’t enough evidence to blanket the symptoms.

“Be cautious if you are thinking about changing your child’s diet and ask yourself whether the invention is for the symptoms or providing a better quality of life for your child.”

A casein-free diet is an eating plan where casein, a milk protein, is removed through dairy products. A gluten-free diet bans wheat, barley, rye, oats and any other food products made from grains.

Children with gastrointestinal problems may find it hard to digest milk protein properly and other studies have found that eating milk proteins can lead to a high level of protein by-products, called casomorphines.

In some autistic children with GI symptoms, casomorphines can reduce the desire for social interaction, block pain messages and increase confusion. The idea behind the elimination process is that it could improve ASD-related behavoiur as a result.

A previous study, by the Mailman School of Public Health at Columbia University, discovered gut bacteria in autistic children is different from non-autistic children.

Another study, by the Autism Treatment Network, discovered that gastrointestinal problems are common in children with ASD, with nearly half of autistic children reported as showing symptoms.