Intestinal permeability and nutritional status in developmental disorders

Autism is a developmental disorder with a possible connection between dietary components and triggering or worsening of symptoms. An altered intestinal permeability might allow absorption of incompletely digested peptides (gluten and casein) that could produce opioid-like activity on the brain, causing significant changes in behavior.

To assess the intestinal permeability and nutritional status of participants with developmental disorders to determine if changes in the intestinal mucosal barrier and/or injury to the intercellular junctions have occurred that might justify application of further dietary modifications.

To assess intestinal permeability, the research team analyzed participants urine under fasting conditions, using gas chromatography to determine chromatographic peaks. To assess nutritional status, the team determined participants heights and weights and performed a bioelectric bioimpedance examination at least 4 hours after their most recent meal. In addition, the team determined food intake using three diet diaries. They asked participants and caregivers to register each food consumed during 2 nonconsecutive weekdays and 1 weekend day.

The study occurred at the Ribeirao Preto School of Medicine, Sao Paulo University.

Seven participants aged 9 to 23 years with developmental disorders (the developmental group, DG) completed the study. The research team recruited them through the Association of Friends of the Autistic Persons of Ribeirao Preto in Ribeirao Preto, Brazil. The control group (CG) consisted of nonsmoking healthy volunteers in the general population who were similar in age to the experimental group and did not suffer from diseases that potentially could influence nutritional status and intestinal function.

To assess intestinal permeability, participants ingested 150 mL of an isosmolar solution of the sugars mannitol (2 g) and lactulose (7.5 g) under fasting conditions and the researchers collected all voided urine over a period of 5 hours.

Using chromatographic peaks, the research team quantified the mannitol and lactulose in participants urine by calculating the percentage excreted in relation to the ingested amounts of sugar. This calculation gave them the lactulose-to-mannitol ratio (L/M). To evaluate nutritional status, they used data regarding bioimpedance resistance, heights, and weights to estimate lean mass and body water (in liters). They classified adults and adolescents using the body mass index (BMI). For children (2-10 y), they classified participants height-to-age and weight-to-height ratios. The research team used food intake to examine the macronutrient interval, the mean added sugar consumption, and the quantity of protein, in g/kg weight.

Participants with developmental disorders (n = 7) were more likely to be overweight. Their usual diet revealed a high intake of lipids (%) and proteins (g/kg) (compared to reference values) and a high intake of calories (kcal) and carbohydrates (%) (compared to CG) as well as a high intake of food sources that are important contributors of casein and gluten. The DGs (n = 7) mean mannitol excretion was lower, and their L/M higher than the CGs (n = 7) (P < .05). Their increased L/M may indicate atrophy of the intestinal-mucosa surface and/or injury to the intercellular junctions or the effect of some other abnormality. The small number of participants, however, prevented more complex statistical analysis.

Researchers need to complete additional studies to confirm the existence of abnormalities in autistic individuals intestines and to justify the use of dietary restrictions on gluten and casein to improve the symptoms of autism.