Body, brain and behaviour More parents are making a connection between the way their child’s gut functions and their behaviour – and noticing that altering their diet can have a lasting effect, says nutritionist Angelette Müller
Angelette Müller has more than 10 years’ experience as a practitioner, educator and culinary health specialist. She has an MSc in Clinical Neuroscience and Immunology and a Postgraduate Diploma in Nutrition Therapy. Angelette is part of the ASD team at the Breakspear Medical Group in the UK, where she works with Dr Daniel Goyal.
The gut is the only organ in the body that has ‘a mind of its own’. The gut-brain, technically known as the enteric nervous system (ENS), is composed of 100 million neurons that directly control the body’s digestive processes; just like the larger brain in our heads, the ENS sends and receives impulses as it oversees gut function. One of the challenges of the gut is that its ‘mind’ can be influenced by the huge population of bacteria that inhabit it, the microbiome. These bacteria play a significant role in the absorption of nutrients, gut barrier health and xenobiotic processing, in other words how the body deals with chemicals that are not naturally found in it. This microbiome can also influence gutbrain communication, affecting brain and behaviour. Scientists do not fully understand how this happens, but there is some suggestion that it involves the amygdala, an area in the brain that processes memory and emotion. Links between the gut, dysbiosis – where there is a bacterial imbalance – and the brain have been reported in a number of psychological and developmental disorders. For instance, dysbiosis has been linked with psychiatric issues in individuals who have irritable bowel syndrome. In an experiment, mice expressed anxious behaviour within seven hours of being infected with
14 Au t i s m | e y e I s s u e 5 2 0 1 2
Campylobacter jejuni, bacteria commonly found in animal faeces that cause human gastroenteritis. Children with autism are commonly reported to have dysbiosis, with related behavioural issues. Carbohydrate malabsorption – when the digestion of starchy foods is impaired - is linked to dysbiosis in the gut. The digestion of carbohydrates begins in the
Improvements include better sleep, less aggression, more focus, better eye contact, more speech and improved understanding” mouth and depends on adequate levels of stomach acid to stimulate the release of pancreatic enzymes, which help to break down large carbohydrate compounds into smaller ones. Finally, brush border enzymes, such as disaccharide enzymes, split the disaccharides into simpler sugars called monosaccharides. These monosaccharides then cross from the gut into the body. A 2011 study6 found a 93% deficiency of disaccharide enzymes in autism. This results in an increased build-
their child after this diet. We need to look at whether this type of diet can improve gut flora, reduce dysbiosis and impact absorption. Diets such as the SCD, or a gluten-free diet, may also need modification if carbohydrates and sugar alcohols known as FODMAPS (Fermentable Oligosaccharides, Di-saccharides, Mono-saccharides And Polyols) are poorly absorbed or not digested at all. These can then promote symptoms of bloating, diarrhoea and flatulence. Fructose, or ‘fruit sugar’, malabsorption can sometimes be an issue. Thus honey, while recommended on the SCD, may cause issues through excess fructose intake, as may high-fructose fruits such as apples, pears, mangoes and watermelon.
up of partially digested carbohydrates, acting as a food source for bacteria and potentially leading to bacterial overgrowth. The role of undigested carbohydrates in developmental disorders has prompted many parents to reduce starchy carbohydrates and follow grainfree diets for their children, such as the specific carbohydrate diet (SCD). This diet excludes all starchy carbohydrates such as wheat, rye, barley, oats, maize and rice, as well as gluten-free pseudograins such as quinoa, buckwheat and amaranth. Starchy foods such as potatoes, cassava, sweet potato and additional vegetables are considered to be ‘too starchy’ or difficult to digest and are also excluded from the diet. A comprehensive list can be found at www.breakingtheviciouscycle.info/ legal/legal_illegal_a-c.htm.
Fructose and emotion
Essential planning Foods that are allowed in the diet are meats, fish, certain vegetables, fruit, nuts, soaked lentils or white beans, home-made yoghurt, honey and cheeses. The introduction of foods can be undertaken in different phases, and direction by a doctor or nutritionist is necessary. Planning is essential for this type of diet, as replacements for commonly eaten foods such as bread, crackers, pasta, dough bases or pastry, rice and potatoes need to be found. Vegetables usually need to take the place of these foods, and nut flours are often used to make baked alternatives to breads and cakes. Challenges such as self-restriction of vegetables or nut sensitivity can sometimes cause problems, so supervision is necessary. No peer-reviewed trials have been published to show how well the SCD works in children with autism, but limited published material is available on this subject. One internet publication compared the effects of a gluten- and caseinfree diet with an SCD in four children. These children were split into two groups. One group was placed on a gluten- and caseinfree (GFCF) diet and the other on an SCD. Physiological and behavioural responses were www.autismeye.com
Eating their way to health: children with autism often have gut problems that special diets may address
recorded for both diets. Positive behavioural changes listed for children on the SCD included no night-waking, fewer tantrums, more and clearer speech, loss of head banging, and less screaming and crying. The limitations of this type of observation include the small number of patients studied, the variation of severity and symptoms in the individuals on the autistic spectrum who took part, and varying treatment response rates.
In clinical practice parents often report positive behavioural and symptomatic changes in response to the SCD. Improvements include better sleep, less aggression, more focus, better eye contact, more speech and improved understanding. Often these improvements have been reported in addition to any changes a child has already gained from following a GFCF diet. However, not all parents have reported benefits in
Lower-fructose fruits can sometimes be used, such as kiwis or berries. Interestingly, in fructose malabsorption, lowering fructose intake was associated with a reduction in depression, illustrating a link between poorly absorbed carbohydrates and mood. Research shows that high fructose in those with fructose malabsorption can modulate tryptophan regulation, potentially influencing the body’s levels of serotonin, which affects our emotional state. Other FODMAPS can individually or collectively influence gut-related symptoms in autism. This highlights the importance of evaluating the diet during treatment to decide if further individualisation needs to take place without restricting foods unnecessarily. Looking at the effects of dietary carbohydrates on dysbiosis, brain, gut and behaviour is still in its infancy. Further research is needed on how different components of the diet can affect intestinal health and, therefore, behaviour.
Bibliography 1 Barrett JS, Gibson PR. Clinical ramifications of malabsorption of fructose and other short-chain carbohydrates. Pract Gastroenterol. 2007:54-65. 2 Collins SM, Bercik P. The relationship between intestinal microbiota and the central nervous system in normal gastrointestinal function and disease. Gastroenterology. 2009;136:2003-14. 3 Cryan JF, O’Mahony SM. The microbiome-gut-brain axis: from bowel to behavior. Neurogastroenterol Motil. 2011;23:187-92. 4 Heijtz RD, et al. Normal gut microbiota modulates brain development and behavior. Proc Natl Acad Sci USA. 2011;108:3047-52. 5 Licht TR, et al. Dietary carbohydrate source influences molecular fingerprints in the rat faecal microbiota. BMC Microbiol. 2006 Nov 30;98. 6 Williams BL, et al. Impaired carbohydrate digestion and transport and mucosal dysbiosis in the intestines of children with autism and gastrointestinal disturbances. PLoS One. 2011;6(9):e24585 www.autismeye.com
Au t i s m | e y e I s s u e 5 2 0 1 2 15