The debate about diet and autism

Paula Goodyer

"Boy recovers from autism after going gluten free."

"Gluten- free casein-free diet no remedy for autism."

Welcome to the conflicted world of diet and autism where opinion over the benefits of removing gluten (the protein in wheat, rye and barley) and casein (the protein in milk) from the diet is divided. Depending on which website you click on, the gluten-free, casein-free diet is either saviour or undiluted snake oil.

Between these polar opposites is a grey area with not much to go on - and definitely nothing on which to hang a claim that diet cures or causes Autism Spectrum Disorder - the term covering a range of developmental problems including autism, Asperger's syndrome and atypical autism. There are anecdotes from some parents and health professionals that dietary changes including the gluten-free casein-free (GFCF) diet can improve behaviour, along with some studies showing a benefit for a change of diet in some children - but others showing no benefit at all. Muddying this picture even more is the fact that some studies are only short term and include only small numbers of children.

But where there's no argument is that many children with ASD have significant digestive problems - some estimates put this at 30 per cent of children with ASD, others at 50 per cent or more.

"Both the American Academy of Paediatrics and New Zealand Department of Health now recommend that children with ASD be checked for gastrointestinal problems," says paediatrician Dr Leila Masson who spoke about ASD and diet at the recent Nutrition in Medicine Conference held in Sydney.

"But treating these children with the GFCF diet is controversial and we need more research. We don't have much treatment for autism and we don't even understand what causes it," she says. "But in my clinical experience, about 70 per cent of parents say that children become more connected with other people and more interactive when they try it."

So how might a diet minus gluten and casein influence a child's behaviour?

It hinges on a couple of interlocking theories. One is that some children with autism have a leaky gut, meaning the lining of the gut is more permeable than it should be, allowing molecules that are meant to stay within the gut wall to stray into the bloodstream, causing problems. (This isn't far fetched - there's evidence linking gut permeability to a number of disorders including type 1 and type 2 diabetes.) The second theory is that some children with autism lack an enzyme needed to break gluten and casein down, resulting in the formation of opioid peptides - which can then pass through the leaky gut, cross the blood-brain barrier and mess with brain function.     

"Tackling gut issues in these children is important  - they often experience gut pain, constipation, diarrhoea, bloating or gas to  varying degrees, " says an Accredited Practising Dietitian who's used a range of approaches to treat gut problems in children with autism for 20 years. But identifying the cause of these problems is complex, she adds. There's no one-size-fits-all solution.

"Anecdotally, I know that gluten and casein can play a role but there are many other possibilities too - FODMAPS, a group of fermentable carbohydrates found in some foods that can cause gut pain in some people, is just one example," she says. "Each child needs an individualised approach and any dietary changes should be done in collaboration with a doctor and dietitian. You can be well nourished on a GFCF diet if it's well planned but there are pitfalls such as insufficient fibre or B vitamins - especially if the diet includes a lot of processed gluten-free foods.  Calcium is important for a wide range of functions in the body - not just bone density - so if a child's going to avoid dairy products it's important to make sure they get sufficient calcium from other sources, along with vitamin D to help absorb calcium. You have to make sure you don't resolve one issue and create another - like stunted growth or the risk of osteoporosis."

"There's no question that the number of children with ASD who have gut problems is higher than what would normally be expected in children generally but how this might relate to diet is still very murky," adds Professor Andrew Whitehouse of the Telethon Kids Institute in Western Australia, which is doing a study to see if fish oil supplementation improves learning in children with ASD.

"I see parents who swear black and blue that changing their diet has helped their children and my answer is 'I believe you but at the moment there's  little scientific evidence  to say that changing the diet improves autistic behaviours  - so go into it with your eyes open'. We need more evidence to guide clinical decision-making."

ASD isn't one single disorder, he explains. It's many different conditions, all with a similar cluster of symptoms - and what causes autism in one child may be different to what causes it in another.   

"But this 30 per cent of children with gut problems may provide a clue to understanding the causes of autistic behaviours in some children," Whitehouse says.