Prebiotic supplement use, the gut microbiome and behaviour change in children with autism spectrum disorder (ASD).

We will conduct a 6-week double blind RCT in which the intervention group (25 children with a clinical diagnosis of ASD, aged 4 to 10 years) will be given a daily dose of 2.4g of prebiotic galacto-oligosaccharides (ßGOS) divided into 4 doses of 0.6g. Each dose is contained in a capsule which should be opened and the powder mixed into 100mls of fluid / drink. Compliance will be measured by counting returned capsules on completion of the intervention, and by a supplement diary which asks a tick for each dose administered. The supplement is to be given under supervision of the parent / carer. A parent or carer of the child participant will attend 2 research visits, the first on day 1 (baseline) and the second on day 43 (completion) of the intervention. These visits will last 1 hour. During these visits, completed questionnaires and clinical samples will be collected (see attached protocol), and standardised dietary advice will be given by one paediatric dietitian (JP), focusing on promoting positive mealtime environments, reducing stress around mealtimes and focusing on small steps involving sensory acceptance of foods.