Background: Autism spectrum disorder (ASD) is one of the most prevalent neurodevelopmental disorders. Many patients with ASD often show behavioral problems at mealtimes, including food selectivity and atypical feeding behaviors. The Mediterranean diet (MD) has a beneficial effect on mental health for the general population across different ages. There is evidence that good adherence to the MD is effective in reducing peripheral inflammatory markers, such as the cytokine interleukin-6 (IL-6). The present study was designed to evaluate adherence to the MD in children with ASD using age- and sex-matched, typically developing individuals (TDs) as a control group and to determine whether differences in adherence to the MD are associated with salivary IL-6 and IL-6 receptor concentration. Methods: Twenty children and adolescents with ASD (mean age 9.95 ± 0.65 years) and twenty TDs (mean age: 9.85 ± 0.59 years) participated in this study (N = 16 males and N = 4 females in each group). Participants with ASD were enrolled in a psychiatric consultation in Valencia (Spain), and TDs were recruited from two public schools in Valencia. The parents of both ASD and TD groups answered the items in a validated Mediterranean Diet Quality Index for children and adolescents (KIDMED) questionnaire on their children’s adherence to the MD. Results: The mean adherence to MD score was significantly lower in the ASD group (9.10 ± 0.42) (range 6–12) than in the TD group (10.35 ± 0.31) (range 8–12) (p = 0.02, Mann–Whitney U test). There was no statistically significant association between adherence to the MD and age or sex in both groups, but there was a significant correlation between the total KIDMED score and body mass index (BMI) in the ASD group. Regarding the concentration of Il-6 and the Il-6 receptor in saliva samples, there were no significant differences between the two groups; however, linear regression analysis by group revealed significant associations between the adherence to MD score and the concentration of IL-6 and its receptor in saliva in the ASD group (p = 0.003, OR = 0.68, 95% CI 0.007 to −0.02; p = 0.009, OR = −0.64, 95% CI −0.01 to −0.00). In contrast, no significant associations were observed between the adherence to MD score and the concentration of IL-6 and its receptor in saliva in the TD group. Conclusions: Children and adolescents with ASD showed significantly lower adherence to the MD, which can contribute to nutritional deficits described in ASD, and the role of BMI composition (fat versus lean mass) needs to be further investigated in this group. The concentration of IL-6 and its receptor in saliva is associated with adherence to the MD, suggesting a possible link between IL-6 and diet in ASD. Further studies to clarify the associations between IL-6, psychiatric alterations, and diet in ASD are needed.

Background: Sleep disorders are common in youths with autism spectrum disorders. Inflammatory cytokines such as Il-1 beta and Il-6 in saliva have been associated with alterations in sleep quality in various conditions. We assessed whether there were associations between the salivary concentration of IL-1 beta and IL-6 and sleep quality in youths with ASD versus typically developing (TD) age- and gender-matched youths. Method: Forty children and adolescents with ASD or TD participated in this study (20% females). Their parents answered the items of a validated questionnaire on sleep quality (Pittsburgh Sleep Quality Index). Results: The mean Pittsburgh score was significantly higher (i.e., the quality of sleep was poorer) in the ASD group (8.68 ± 0.35 (SEM), ranging from 7 to 12 points), compared to the TD group (7.35 ± 0.54 (SEM), ranging from 2 to 12 points) (p = 0.02, Mann–Whitney U test). There were no significant differences in the salivary concentration of Il-1 beta and IL-6 receptor between the two groups, but salivary IL-1 beta concentration was inversely associated with poor sleep quality in the ASD group. No associations between the salivary Il-6 concentration and sleep quality were found in either group. Linear regression analysis by separate groups revealed significant associations between the sleep quality score and the concentration of IL-1 beta in the ASD group (p = 0.01, OR = −0.53, 95% CI −0.008–0.001). In contrast, no significant associations were observed in the TD group, or for IL-6 in either group. No significant effects of sex, age, or use of psychotropic medications were found. Conclusions: Children and adolescents with ASD showed significantly poorer sleep quality based on their parents’ reports compared to the TD group, and the salivary IL-1 beta concentration was inversely associated with sleep quality only in the ASD group. Further studies on the associations between inflammatory cytokines and sleep in ASD are needed.