Gluten and autism

Autism, or autism spectrum disorder (ASD), is a developmental disability that begins in childhood and which will have an impact on a person for their entire life. ASD can cause significant social, communication and behavioural challenges. 

People with ASD often have difficulties with social, emotional and communication skills. They might repeat certain behaviours and be upset by changes to their daily activities. People with ASD tend to have abnormal ways of learning and paying attention, or reacting to things that happen around them. Some people with ASD have trouble relating to others, avoid eye contact and do not enjoy experiencing physical affection such as hugs. 

There are many subtypes of autism, influenced by a combination of genetic and environmental factors. This means that each person with ASD will have a different set of strengths and challenges. As adults, some may need significant levels of support in their daily lives, while others live independently.  

Signs of ASD begin during early childhood and last throughout the person’s life, although early intervention including behavioural therapy and medication can lead to positive outcomes. ASD is a common condition. According to the Centers for Disease Control, autism affects an estimated one in 54 children in the United States today. Boys are more likely to de diagnosed with autism than girls. 

The idea of a connection between gluten and autism emerged in the late 20th century, with the idea that gluten could worsen autism symptoms by causing inflammation in the gut that then spreads to the brain. The same could be the case with casein, a protein fund in dairy products, or so the theory went.  

The controversial theory is based on the idea that children with ASD have a “leaky gut”, which allows fragments of proteins such as gluten or casein to leak from their digestive tracts. These proteins, so the theory runs, can have an opioid-like effect on a child’s brain, leading to abnormal development. Many children with ASD also seem to have digestive problems, such as diarrhoea, abdominal pain, constipation or reflux, which serves to underline the idea in some people’s minds that there is a connection between autism and diet.  

Some research has found abnormal levels of peptides associated with the incomplete breakdown of proteins gluten, gliadin and casein in the urine of people with ASD, but it is not clear what this might mean.  

In the absence of any effective medical cure for autism, parents of children with ASD understandably seek alternative measures in the hope that they will help their child to develop. The GFCF diet is one method tried by some, and in surveys many parents have indicated that they see improvements as a result of the diet.  

There is no solid scientific evidence to back up the idea that a gluten free or GFCF diet can help to reduce the symptoms of autism, but some alternative practitioners continue to recommend this kind of dietary approach.  

Many studies have been carried out attempting to examine what impact, if any, a gluten free or GFCF diet has on autism. Until recently, few had provided very reliable conclusions, due to a combination of factors such as the small number of participants or the difficulty in assuring that they adhere to a strict diet without any gluten or casein.  

In 2019 a  study was carried out by the University of Warsaw in Poland and published in the Journal of Autism and Developmental Disorders. The study involved 66 children with ASD, half of whom followed a strict gluten free diet for six months, while the other 33 ate a normal diet with gluten in at least one meal a day. When behavioural changes were measured in a standardised way, no differences were found between the two groups.  

A review of major studies on the GFCF diet carried out in 2017 found that this approach had no measurable impact on autistic symptoms. It still may be possible that there is a small subset of children whose autism symptoms are helped by the diet, but it does not seem to be at all effective in general terms. 

Attempts to connect coeliac disease with autism have yet to provide any conclusive results. The largest study to date, conducted in Sweden and using the country’s national health registry, found that people with ASD were not more likely to also be diagnosed as having coeliac disease with a biopsy sample from the intestine.  

However, the same study revealed that people with autism were three times more likely than the population at large to have a positive coeliac blood test. This would suggest that their immune system was reacting to gluten but without this leading to intestinal damage. This could hint at some link between non-coeliac gluten sensitivity and ASD in some cases, but more studies are needed to understand what, if any, connection there is.