The gluten-free, casein-free diet (GFCF diet) is designed to exclude all foodstuffs which contain gluten and casein.
Gluten is a protein found in some cereals such as wheat, rye and barley. Oats contain a similar protein called avenin and are usually processed in the same factories, so are often included in the list of foods to be avoided for people following this diet. Casein is a protein found in dairy products such as milk, butter, cheese and yoghurt.
There are several overlapping theories as to why gluten and/or casein may be harmful to some individuals. For example, some people believe that improperly digested gluten and/or casein (in the form of harmful peptides) may adversely affect the central nervous system. Other people believe that gluten and/or casein may provoke adverse autoimmune responses in the gastrointestinal (GI) system.
Some people believe that harmful peptides and/or adverse autoimmune responses may create some of the core features of autism, such as difficulties with social communication and social interaction, alongside related problems, such as challenging behaviours. They also believe that by excluding gluten and-or casein from the diet, they can prevent these problems.
The National Institute for Health and Care Excellence (2012) made the following observations on the use of exclusion diets for adults on the autism spectrum:
"... there is very little evidence regarding safety and efficacy for exclusion diets ... for the treatment of autism."
The National Institute for Health and Care Excellence (2013) made the following observations on the use of exclusion diets for children and young people on the autism spectrum:
“Do not use the following interventions for the management of core features of autism in children and young people: exclusion diets (such as gluten- or casein-free diets).”
Eating a healthy, balanced diet is recommended for everybody in order to maintain good health. Anyone with a particular condition (in addition to or separate from autism) may be recommended to follow a special diet by a dietitian and this should be followed on an individual basis. For example, dietitians may recommend a gluten or milk exclusion diet for various gastrointestinal problems.
There is some research to suggest that some individuals on the autism spectrum may have significant gastrointestinal problems, although the actual number of individuals with GI problems is unclear. There is no scientific consensus on whether individuals on the autism spectrum do or do not have unusual levels of peptides in their bodies.
Determining if gastrointestinal problems or high levels of peptides cause the core features of autism or related problems is not currently possible. We must wait until further research of sufficiently high quality has been completed.
There have been several randomised controlled trials and several single-case design studies into the use of the gluten-free, casein-free diet for people on the autism spectrum but the results are mixed.
Determining if the GFCF diet has any significant benefits for individuals on the autism spectrum is not currently possible. We must wait until further research of sufficiently high quality has been completed.
The gluten-free, casein-free diet can involve significant inconvenience and cost, as well as significant limitations on what you can eat. It also poses a number of potential risks including a low intake of calcium, iodine and fibre which can lead to weaker bones, iodine deficiency and gut problems (there is also a risk of masking undiagnosed coeliac disease if a coeliac disease test is not carried out before trialling the diet). Because of this, we cannot recommend its use.
However, because the diet is one of the most commonly used interventions for people on the autism spectrum we do strongly recommend that further research is undertaken. This research should use more scientifically robust, experimental methodologies with larger numbers of participants. It should also investigate if there are different subsets of individuals on the autism spectrum (such as those with gastrointestinal problems or those with allergies to gluten and/or casein) who might benefit most from the diet.
Please read our Disclaimer on Autism Interventions