Gluten-Free, Casein-Free Diet for Children with Autism Spectrum Disorder: A Case-Controlled Study

ABSTRACT

Background and Objectives:

Numerous therapeutic and dietary interventions have been examined in the last thirty years for pediatric patients diagnosed with autism spectrum disorder (ASD). Our interventional study aimed to assess the effectiveness of the gluten-free, casein-free (GFCF) diet in a cohort of Egyptian children with ASD

Materials and Methods:

The present clinical trial was conducted as a prospective 12-month, open-label, case-controlled interventional study. Thirty-six ASD children who were newly diagnosed and had not taken any prior psychiatric or rehabilitation therapy were included in this study. The patients were randomly assigned into two groups: group A, which received the GFCF diet, and group B, which served as the control group and was not restricted to food containing gluten and casein for 12 months. All patients were followed up for 1 year.

Results:

Following the implementation of the GFCF diet in group A, significant improvements in CARS scores were observed compared to group B after 6-month and 1-year follow-up periods.

Conclusions:

The introduction of the GFCF diet could be helpful and promising for autistic children. Conclusive evidence regarding the effectiveness of the GFCF diet remains a subject of controversy. Nonetheless, our study contributes some evidence supporting its potential benefits for children with ASD. It is recommended that future research on the GFCF diet employ a more sophisticated research design, incorporating a consistent baseline measure that can effectively assess the therapeutic effects of these interventions for individuals with ASD.

INTRODUCTION

Autism spectrum disorder (ASD) is a heterogeneous neurodevelopmental disorder that typically becomes apparent before the age of 3 years. It is characterized by three primary features: i) disruptions in social interaction, ii) impairments in both nonverbal and verbal communication, and iii) repetitive patterns of interests and activities.[1,2,3] Although the diagnosis of ASD primarily relies on the evaluation of behavioral and clinical criteria, which should recognize deviations in speech, social interaction, deficits in receptive and expressive language skills, and the presence of abnormal repetitive behaviors, individuals with ASD may also exhibit various challenging behaviors such as aggression, reduced attention, self-injury, impulsivity, hyperactivity, and tantrums.[1,3] ASD is currently recognized as one of the most prevalent and widespread neurodevelopmental disorders. The prevalence of ASD has increased due to improved analytical procedures and the recognition of various degrees of autism. According to ADDM, the prevalence of ASD in 8-year-old children in the US has increased more than twofold, from 11.3/1000 in 2008 to 23/1000 in 2018. Now, one in 36 (2.8%) has been identified in 2023.[4] Previous studies have reported many environmental and genetic factors that could play a significant role in the development of autism, including maternal diet and exposure to air pollution or certain pesticides during the prenatal period, in addition to maternal diabetes, obesity, and immune disorders.[5] Autistic individuals often experience gastrointestinal (GIT) symptoms, which may be attributed to factors such as allergic reactions, alterations in gut microbiota, increased intestinal permeability, and intestinal inflammation.[3,6] Studies conducted over the past two decades have revealed evidence of cerebral hypoperfusion, gastrointestinal and neuroinflammation, as well as immune and mitochondrial abnormalities in patients with ASD. Most of these problems have been linked to the core symptoms of ASD.[3,7] Although the exact mechanisms underlying ASD pathogenesis remain unidentified, numerous clinical interventional trials have been developed to manage the condition and alleviate the behavioral and health challenges faced by individuals with autism. Currently, there is no pharmaceutical management that can cure ASD; however, a few studies have reported the potential efficacy of the gluten-free, casein-free (GFCF) diet.[7,8] The GFCF diet involves the exclusion of two proteins, casein and gluten, from the diet. Casein is present in all dairy products, while gluten is commonly found in oats, wheat, barley, and rye. This dietary approach, known as GFCF, is widely adopted to address GIT symptoms in children with ASD.[8] Although the evidence is inconclusive, the GFCF diet has shown the potential to partially improve certain symptoms associated with ASD and enhance developmental outcomes in some ASD patients.[7] The objective of our study was to assess the effectiveness of the GFCF diet in a group of autistic children in Egypt.

Patients and methods

This study was conducted in accordance with the ethical guidelines outlined by the World Medical Association’s Declaration of Helsinki. Approval for all procedures was obtained from the Ethical Committee of Al-Azhar Faculty of Medicine, Egypt. Prior to participation, patients’ caregivers received a detailed explanation of the study, and written consent was obtained in accordance with the guidelines set forth by the Ethical Committee.

Study design

The study was a prospective 12-month, open-label, case-controlled interventional clinical trial. The research was conducted at the outpatient clinics of two tertiary Hospitals in Assiut, Egypt, throughout the years 2021 and 2022.

Participants

A total of 36 Egyptian pediatric patients diagnosed with ASD were selected from a larger pool of 55 children. These individuals were recruited from our outpatient clinics and were recently diagnosed with ASD. None of the participants had received any prior rehabilitation therapy, and they were all in a generally healthy condition. Among the initial sample, nine patients were excluded based on predefined exclusion criteria outlined in Table 1. In addition, 10 patients were excluded as their families declined to join the study. All participants were recruited from the outpatient clinics of Al-Azhar and Assiut University Hospitals in Egypt.

Table 1.

Exclusion criteria

1. Other metabolic and neuropsychiatric disorders, e.g., epilepsy, urea cycle disorder, and cerebral palsy.

2. Faltering growth or chronic malnutrition.

3. Children with anemia and autoimmune disorders.

4. Patients taking any of the following medications: steroids, diuretics, multivitamins, diltiazem, thiazide diuretics, verapamil, and digoxin.

5. Poor oral intake.

6. Cardiomyopathy.

7. Children with known chronic systematic diseases.

MATERIALS AND METHODS

The enrolled patients were randomly divided into two groups:

Group A: This group consisted of 19 patients who were provided with a GFCF diet tailored to each individual’s age and daily energy requirements, following the approach described by El-Rashidy et al.[7] Patients were offered alternative food options free from gluten and casein, and a metabolic kitchen at our university supplied the necessary foods. A qualified nutritionist assessed the baseline data of all participants, and the GFCF diet was gradually implemented over 1 month, with weekly assessments of nutritional status. Prior to initiating the GFCF diet, three meetings were conducted with caregivers to explain the implementation process. Families were provided with instructional materials detailing the foods containing gluten and casein, and they were trained to read food labels accordingly. Written nutritional regimens specifying calorie requirements were given to parents. Families were also instructed on how to document a 24-hour food recall. Weekly appointments at the nutrition clinic were mandatory to evaluate the patients’ compliance through the 24-hour recall and adjust the diet as necessary.

Group B: This group consisted of 14 patients who were not restricted from consuming foods containing gluten and casein throughout the 12-month study period.

Psychiatric assessment

The same psychologist established the diagnosis of ASD for all patients included in the study. The diagnostic process followed the criteria outlined in the DSM-5.[9] In addition, the diagnosis was confirmed, classified, and monitored using the Autism Diagnostic Interview-Revised (ADI-R)[10] and the Childhood Autism Rating Scale second edition (CARS II).[11]

The diagnostic process involved two separate interviews with parents, each lasting at least 30 minutes. The first interview focused on establishing the diagnosis of ASD according to the DSM-5 criteria and utilizing the ADI-R. The second interview was conducted to assess the severity of ASD by using CARS II. CARS II evaluates autistic behaviors across 14 domains and includes a parameter for providing an overall impression of autism, enabling differentiation from other developmental disorders.[11]

CARS assessments were conducted before the commencement of interventions and were repeated at the 6-month and 12-month follow-up points to evaluate changes in ASD severity over time.

RESULTS

The study included a total of 36 children (29 males (80.6%) and 7 females) newly diagnosed with ASD. The mean age of the patients was 3.5 years, ranging from 2.5 to 6 years. Baseline assessments using the CARS indicated scores ranging from 30 to 55, with a mean score of 36.7. At the start of the study, no significant differences were observed between both groups [Table 2] in terms of age, sex, anthropometric data, and autism classification. Following the implementation of the GFCF diet in group A, significant improvements in CARS scores were observed compared to group B after a 6-month and 1-year follow-up period [Table 3].

Table 2.

Characteristics of all study subjects

Variable	Group A (n=19)	Group B (n=17)	P
Age, years
Range	2.5-5	2.5-6	NS
Mean±SD	3.00±1.25	3.5±1.5
Sex [Number (%)]
Males	15 (79%)	14 (82%)	NS
Females	4 (21%)	3 (18%)
Childhood Autism Rating Scale (CARS)
Range	30.5–53.5	30–55	NS
Mean±SD	36.9±4.8	36.4±5.3	NS
Mild/moderate (≤36.5) Number (%)	12 (63%)	11 (65%)	NS
Severe (≥37) Number (%)	7 (37%)	6 (35%)	NS
Autism Diagnostic Interview-Revised (ADI-R)
Communication	17.1±5.4	18.9±3.8	NS
Stereotyped behavior	3.7±1.0	3.2±1.1	NS
Social interaction	11.4±3.3	13.1±4.2	NS
Play	4.9±1.7	4.3±2.3	NS

NS=Non-significant

Table 3.

Comparison between A and B by CARS raw scores

Mean±SD	CARS 0 (At baseline)	CARS 1 (After 6 months)	CARS 2 (After 12 months)	P (1)
				0 vs. 1	0 vs. 2	1 vs. 2
Group A (n=19)	36.9±4.8	32.6±2.1	31.9±6.7	0.001*	0.001*	0.02*
Group B (n=17)	36.4±5.3	36.5±1.2	35.9±3.4	0.001*	0.001*	0.001*
P (2)	0.153	0.023*	0.001*

⁽¹⁾Comparison between different CARS using the Wilcoxon signed-rank test. ⁽²⁾Comparison between groups A and B by using the Mann–Whitney test. *Significant level is taken at P<0.05. Group A: restricted diet for 12 months. Group B: not restricted diet for 12 months

DISCUSSION

In an effort to alleviate the core symptoms of ASD, various complementary or alternative treatments have been utilized, including immune therapy, vitamin supplements (particularly vitamin D and polyunsaturated fatty acids), and, more recently, special diets.[6-8,12] The current trend is to adopt multiple therapeutic approaches that may synergize to achieve optimal outcomes based on the intervention stage and severity of ASD. However, the lack of rigorous studies and conflicting results have hindered the ability to draw definitive conclusions regarding these treatments for ASD.[1,13] In our study, we observed a significant improvement in CARS scores after 6 and 12 months of follow-up in subgroup A, which received the GFCF diet. This suggests that the GFCF diet serves as a cofactor in improving autism symptoms. Our findings are supported by a previous study conducted by El-Rashidy et al.,[7] which assessed the efficacy of GFCF in 15 children with ASD over a 6-month period. The study reported that patients who received the GFCF diet exhibited improvements in total CARS scores and in speech and behavior assessed by the Autism Treatment Evaluation Checklist (ATEC) compared to baseline scores and the control group. Similar results have been reported by other studies.[14,15] Pedersen et al.[15] conducted a controlled clinical trial with an adaptive design, showing significant differences between the dietary and non-dietary groups, indicating a positive effect of the GFCF dietary intervention. These results were consistent with those of Whiteley et al.[14] and Pennesi and Klein,[16] who found that GFCF was particularly effective in improving social behaviors in autistic children. Furthermore, ASD patients with food allergies and/or sensitivities and gastrointestinal symptoms demonstrated more significant improvement when compared to other ASD children.[16] However, contrasting results have been reported in some studies. Johnson et al.[17] and Pusponegoro et al.[18] found no significant differences between ASD groups receiving the GFCF diet and those who did not. It is worth noting that the duration of the GFCF diet in these studies was relatively short (<3 months), and methodological differences between these studies and ours may account for the divergent findings. The main limitations of our study include the absence of a double-blinded evaluation and the small sample size. Recruiting patients proved to be challenging as many caregivers declined participation and were hesitant about implementing a special GFCF diet.

CONCLUSION

The introduction of the GFCF diet could be helpful and promising for autistic children. Conclusive evidence regarding the effectiveness of the GFCF diet remains a subject of controversy. Nonetheless, our study contributes some evidence supporting its potential benefits for children with ASD. It is recommended that future research on the GFCF diet employ a more sophisticated research design, incorporating a consistent baseline measure that can effectively assess the therapeutic effects of these interventions for individuals with ASD.

Ethics approval

The study was conducted as per the Declaration of Helsinki, and the Ethics Committee of the Faculty of Medicine, Al-Azhar University reviewed and approved the research (N: 2023/7).

Consent to participate

All caregivers of all participants have given their informed written consent.

Availability of data and materials

The datasets used and/or analyzed during the current study are available from the corresponding author upon reasonable request.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.