Health problems challenge human lives in a variety of ways. It is necessary to address for help, be diagnosed, and follow a treatment plan. When a person has to deal with several diseases at the same time, the situation gets worse, especially if a patient is a child. In this paper, the relation between food allergies and autism spectrum disorder (ASD) in paediatric patients will be investigated. One should understand that autism is not an illness but a condition when the brain works differently compared to other people (National Health Service, 2019a). There are no cues to treat autism, and people have to live with this condition their whole lives.
Almost the same situation is observed in people with food allergies. This type of allergy is a condition when the immune system reacts to a specific food as a possibility to defend itself against infection (National Health Service, 2019a). A positive association of food allergies with ASD was found (Xu et al., 2018). The summary of sources about autism and food allergies will help identify the characteristics of this relation and choose the best food diet plan for autistic children.
Autism and Food Allergies: Separately and Linked
Autism and a food allergy are the two different conditions that are usually detected in early childhood and become lifelong disorders. The Centers for Disease Control and Prevention explains that one in 37 boys and one in 151 girls had the diagnosis of ASD in 2018 (as cited in Autism Speaks, n.d.). Relying on the results of different studies, major characteristics of ASD include impairments in social communication and interaction, repetitive behaviours, and restricted interests (as cited in Lyall et al., 2017).
Although autism is usually defined as a heritable (genetic) condition, some environmental factors like parental age, interpregnancy interval, or maternal hospitalisation due to infection, may also be implicated (Frustaci et al., 2012; Lyall et al., 2017). Food allergies change the lives of more than 32 million Americans, including 5.6 million children younger than 18 years (Food Allergy Research & Education, n.d.). More than 170 types of food may cause an allergic reaction, including milk, egg, honey, peanut, and fish (Food Allergy Research & Education, n.d.). As a rule, first allergic reactions developed in childhood and may be of different types, depending on pathogenesis mechanisms.
Autism Spectrum Disorder in Children
The development of a child is a complex process that is characterised by multiple interventions and challenges. Parents try to do everything to protect their children and provide them with the best living conditions. However, ASD is hard to predict and control, with its conditions appearing during the first five years of life (World Health Organization, 2018). Many sources define autism as a lifelong disability, and people can never get rid of its symptoms but are able to live a good life (Moulton, Barton, Robins, Abrams, & Fein, 2016; National Health Service, 2019b; Orinstein et al., 2015).
There are also the studies that prove the possibility of “optimal outcomes” in treating pathophysiological comorbidities and “recovery from autism” when a child no longer meets diagnostic criteria (Barnevik Olsson et al., 2015; Frye & Rossignol, 2016). Hus Bal, Fok, and Lord (2017) explain that autism development may gain different trajectories, including the improvement as language develops or a person gets older, relative stability, and changes in a developmental context. In all these studies, authors support the idea that autism in children is not the reason to believe that nothing can be done.
Food Allergies in Childhood
Along with autistic characteristics, paediatric patients may be challenged by a number of additional diseases and conditions. A food allergy is one of the most frequent reactions of the body to particular products. Allergies may be mild when an itchy moth or hives bother a child or severe when throat tightening and difficult breathing threat the child’s life (Food Allergy Research & Education, n.d.).
Depending on the symptoms, three major types of allergies exist (National Health Service, 2019a). IgE-mediated food allergy is observed in about 3% of the population and characterised by anaphylaxis because of the high-level production of immunoglobulin E (IgE) (Valenta, Hochwallner, Linhart, & Pahr, 2015). Non-IgE-mediated food allergies are caused by other cells of the immune system, and it takes time to recognise this reaction. Mixed allergies (IgE- and non-IgE-mediated) are observed when people experience symptoms of both types.
There are many ways to predict the development of allergies. Some families like the idea of avoidance of harmful products and prediction of possible health complications. Turke (2017) discussed the relationships with the “old friends” (worms, bacteria, and viruses that may live in/on the body) that people must develop. In autistic children, food allergies are frequent because of the impossibility to learn the threat of allergic products or recognise a problem on its early stage.
Relation Between Autism and Food Allergies
Many parents of autistic children observe a relation between ASD and food allergies. Autism Speaks (2017) reported that autism is explained as a whole-body disorder that includes such comorbidities as gastrointestinal disorders, eating or feeding challenges, and seizures. Being a complex organ of the immune system and the “second brain” due to enteric nerves, the intestinal tract completes a neurological function (de Theije et al., 2014). When the intestinal immune system is disturbed by outside factors, behavioural and emotional changes may be observed.
It is said that “enhanced internalising behaviour and a trend towards low social emotional scores” are associated with food allergies, and children with ASD frequently have intestinal problems (as cited in de Theije et al., 2014, p. 266). Although no one can explain what comes first, an allergy or autism, their correlation remains a significant topic for discussions in different countries. The influence of food allergy on the nervous system has been proved by Xu et al. (2018). Alterations in the gut microbiome and allergic immune activation provoke new neurodevelopmental abnormalities among children with ASD, the prevalence of which has considerably increased during the last several decades.
Preventive Diets and Food Plans to Reduce Autistic and ADHD Behaviours
Considering the already proved connection between food allergies and autism and the possibility to reduce symptoms of both conditions, it is expected that researchers focused on the discussion of preventive steps and treatment plans. Some scientists and healthcare workers believe that a properly chosen diet and food can reduce hyperactive behaviours in children (Ly et al., 2017). Parental involvement, education, community support, and communication play a crucial role in such autism preventive intervention for paediatric patients (Kerns, Newschaffer, & Berkowitz, 2015).
Autistic children usually have impeded self-sufficiency skills and are challenged by daily living activities, so they are in need of ongoing support offered by their family members (as cited in Spain et., 2017). The research by Solomon et al. (2017) demonstrated that about 37% of autistic children undergo considerable intellectual development from age 2 by age 7, and about 30% experience symptoms’ reduction. Therefore, enough evidence to reduce ASD behaviours may be found today. Along with the autism-allergy connection, one should admit that the control of food intake is one of the potential options for ASD patients to improve their skills.
There are some foods that can worsen autism symptoms, including dairy products, gluten, and sugar. Gluten and casein are the proteins whose abnormal metabolism may lead to excessive opioid activities and challenge the work of the nervous system (Piwowarczyk, Horvath, Łukasik, Pisula, & Szajewska, 2017). In some cases, autistic children experience feeding difficulties because of the inherent inability to take products of specific colour, form, or texture (Pineles, Avery, Liu, 2010). As a result, vitamin (A or B12) deficiency is developed due to the absence of meat or dairy products in the body causing the cases of optic neuropathy, anaemia, DNA methylation, or tumour necrosis (Fenech, 2012; Pineles et al., 2010; Zhang et al., 2016).
As cited in Valenta et al. (2015), “wheat amylase trypsin inhibitors and certain milk oligosaccharides” may provoke new intestinal inflammation processes because Toll-like receptor 4 is activated (p. 1121). Immune mechanisms cannot be challenged by poorly chosen food, so paediatricians and caregivers decide to choose preventive diets and reduce attention-deficit hyperactivity disorder (ADHD) or ASD behaviours.
A possibility of an autistic child to live a healthier life and reduce ADHD and ASD behaviours is a responsibility of parents. Orinstein et al. (2015) based their study on the fact that, in 20% of ASD patients, such comorbidities as ADHD or social anxiety are observed. Therefore, as soon as symptoms of these disorders are defined, and a child meets an ASD diagnostic criteria, healthy food plans are developed as a part of therapy. Diets are usually based on the removal of one or several substances (sugar, flavours, or sweeteners) because they are believed to cause symptoms of autism or, at least, making them worse (Interactive Autism Network, 2008). It is important to test a child for the most common and expected allergies and make sure that a new product does not provoke new complications.
To predict the development of symptoms, it is recommended to put autistics children from an early age to 18 years of age on specific diets. In the majority of cases, researchers prefer to follow gluten-free and casein-free food plans (Piwowarczyk et al., 2017). As soon as the reduction of inflammation processes in the intestinal tract is promoted, children can improve their food selectivity and follow their ordinary steps. Selective eating, as a well-known feature of autism, is a benefit and a challenge for parents. On the one hand, they are able to identify the basic needs of their ASD children and reduce the number of unpredictable behavioural changes and stresses.
On the other hand, in case the same order or traditions are not followed, the child’s behaviour turns out to be hard to control, and the outcomes of such unpredictable food products promote new problems. Frye et al. (2013) concluded that safe nutritional interventions positively influence the daily living, social, and communication skills in children. Similar repeated presentations, escape prevention, and the establishment of a regular meal schedule help parents and children get used to new and old product equally.
The choice of a particular dietary plan for autistic children is also a good chance to avoid new allergic reactions. Valenta et al. (2015) identified the importance of diets as a possibility to ensure balanced nutrition, improve the quality of life, and eliminate unfavourable products. To reduce the problems associated with nutritional deficiencies, paediatricians and dieticians cooperate with families and offer autism-friendly communication tools to increase nutrition and exercises (Autism Speaks, 2017). Discussing the relation between allergies and autism, it is also important to mention that food plans must be healthy in regard to the fact that autistic children are less physically active then typically developed children. Therefore, the consumption of food must be properly evaluated from emotional, physiological, and behavioural perspectives.
Gut Microbiota and the Nervous System
During the last several decades, the gut microbiota has been identified as a topic for research in the fields of biology, psychology, and health care. It is a well-known fact that the human gut is a source of multiple microorganisms like bacteria or fungi. Although the body is one of the best places for viruses to grow, the years of common development resulted in a beneficial symbiotic state of the gut bacteria (Zhu et al., 2017).
These microorganisms play a crucial role in homeostasis development and determine metabolic functions. Contributions to food digestion and the production of vitamins are also defined as the merit of the gut microbiota. Gut-associated lymphoid tissues improve the work of the immune system (Zhu et al., 2017). Children get the gut microbiota from their birth and milking, which formulate the intestinal flora for the rest of life (Bell, Ferrão, & Fernandes, 2018). There is an opinion that the gut flora may affect the work of nerve cells (Zhu et al., 2017). Therefore, digestive bacteria that developed in the intestines of children with autism are abnormal and dangerous sometimes.
There are many cases when medications that are used to help a patient relieve symptoms lead to new problems. For example, Clostridia and similar bacteria produce propionic acid and other fatty acids that remain resistant to antibiotics (Bell et al., 2018).
These species have a tendency to grow in the gut soon after the course of antibiotics and cause new intestinal inflammation that increases the risks of autism or its symptoms worsening. When patients who are on a diet without folic acid take antibiotics as a part of treatment, the chosen drug eradicates folate, produces new dangerous bacteria in the gut, and provokes autism (Fenech, 2012). In their investigation, Piwowarczyk et al. (2017) discovered the effect of “leaky gut” according to which the gut barrier weakens and allows gluten or casein reaching the bloodstream and the nervous system. Such a situation also leads to a new metabolic defect and the growth of ASD symptoms. All these examples prove that the gut microbiota is able to regulate the processes in the central nervous system from the neural and immune points of view.
As soon as a problem is observed in the human gut, the production of unfavourable chemicals cannot be controlled. In a short period of time, some brain functions undergo considerable changes (due to the amounts of serotonin or dopamine). In ASD patients, even insignificant changes in the brain can result in new problems and uncontrollable behaviours. Therefore, the gut microbiota is not only a mediator of risk factors but a protective means that has to remain stable (Zhu et al., 2017).
Observations of autistic behaviours prove that repetitive (stimming) behaviours like hand flapping or obsessive talking are frequent activities that cannot be ignored or controlled (Randall et al., 2018). If one step is missing, the whole process can be put under threat, and autistic children start crying, scaring, or hiding. Similar processes are observed in the gut – when a problem emerges in one part of the body, the whole system may be broken with time. Instead of thinking about what can happen to the nervous system due to the information and products of the outside world, it is better to predict negative outcomes.
The relationship between the central nervous system and the gut is also known as the microbiota gut-brain axis. It is one of the pathways for communication between the gut and the brain that touches neuroendocrine and neuroimmune systems (Zhu et al., 2017). The gastrointestinal tract dominates over the enteric nervous system due to the number of neurons that regulate gastrointestinal functions. Food intake determines the composition of the gut microbiota, thus influences the quantity and quality of microorganisms that reach the brain. If there is no allergy on milk, mothers prefer to feed their children with breast milk.
They want to be sure that the gastrointestinal tract has enough necessary and healthy microorganisms to support the child’s wellbeing and ASD symptoms’ control. However, when an autistic child is allergic to breast milk, additional injections, probiotics, and fermented food have to be considered as a new option for families to control ASD and ADHD symptoms and behaviours.
Probiotics and Fermented Food for Autistic Kids
In addition to healthy food diets that replace specific products from the child’s life, scientists discover new methods to cure autism or reduce its symptoms. Hendren et al. (2016) investigated the worth of methyl B12 injections at the DNA level to improve impaired methylation capacity in ASD children. A relatively small sample due to the necessity to work in laboratories with small children limited the study, and this topic remains poorly investigated. A similar situation was observed in the use of vancomycin, an oral antibiotic, directed to the Clostridium genus responsible for gastrointestinal symptoms in ASD children (Frye & Rossignol, 2016).
Although temporary improvements were observed, this type of treatment is still neither totally approved by healthcare organisations nor supported by families. Much attention is now paid to the role of probiotics and fermented food and their possibility to reduce poisonous effects and improve flavour (Bell et al., 2018). Piwowarczyk et al. (2017) explained probiotics as one of the most successful alternative treatments for ASD children to be offered to families. They are characterised by certain benefits and shortages that have to be mentioned in the discussion of food plans.
Modern mothers, regardless of their age or geographical location, hear the need to add probiotics to their children’s food. Probiotics are defined as “good, or healthful, bacteria, traditionally found in cultured food products such as yoghurt and kefir… and kimchi” (Autism Speaks, 2017, p. 7). Although it sounds strange for many parents to add bacteria to the products consumed by their children, human and animal studies demonstrate promising results for behavioural improvements. In case of autism, children who use probiotics regularly reduce the number of problems associated with social avoidance and repetitive habits (Autism Speaks, 2017). In addition, the use of probiotics helps to restore the number of good bacteria after the use of antibiotics. By its good nature, these bacteria keep the necessary balance between other bacteria or viruses in the body.
The role of probiotics in helping ASD children to restore their gut system is a challenging topic for analysis. On the one hand, there is enough evidence to prove that probiotic-based treatment could result in positive behavioural changes and stool consistency (Frye & Rossignol, 2016). On the other hand, as well as the majority of bacteria, probiotics may have a tendency to damage the gut system and influence the work of the nerves in the body.
Therefore, it is necessary to analyse as many studies as possible to clarify if probiotics can help ASD children in controlling their symptoms. Still, the Food and Drug Administration (FDA) does not consider probiotics as medications but define them as supplements, which results in the lack of professional and safety control (Autism Speaks, 2017). There is a threat that a helpful probiotic can be mixed up with a harmful bacterium, and a child is exposed to some negative effects of the product not because of its poor qualities but because of the lack of control.
Fermented food is one of the available options for children to improve their health and avoid gastrointestinal complications. Child’s nutrition begins with milk, and fermented dairy products have been promoted since ancient times (Bell et al., 2018). People use fermentation processes to preserve food and determine their healthiest qualities. Lacto fermentation occurs when “natural bacteria or yeasts feed on the sugar and starch in the food creating lactic acid” (Bell et al., 2018, p. 1).
The most known products that are derived from fermentation are beverages like wine, cider, or beer and food like yoghurt, fish, meat, or cheese (Bell et al., 2018). The probiotic activity is one of the main benefits of fermented food because these bacteria are able to prevent illnesses. Such characteristics of fermented food as hormone balance, the strengthening of the immune system, and the control of chronic inflammations serve as the main reasons for mothers to include it to the child’s diet. Bell et al. (2018) also mentioned that fermented milk products could block the absorption of phytonutrients. Being critical natural chemicals obtained from plants and plant-based food, phytonutrients help the body to work properly.
The use of probiotics and fermented food for babies is predetermined by the improvements of the gut flora. In the investigations by Bell et al. (2018), coconut kefir, sweet potatoes, and sauerkraut are the most frequently offered fermented products to broaden their food interests and keep safety measurements. Many children prefer sweeteners and sugar to other healthy products. The introduction of fermented products is a good opportunity for parents to control their desire and consume less sugar without any behavioural or emotional changes. Compared to breast milk that is full of healthy fat and other necessary bacteria, everyday food does not contain the necessary amount of biological elements and vitamins.
Bell et al. (2018) recommended fermented food with probiotics as medicine for children that can improve digestion and nutritional content. ADHD and ASD children suffer from the leaky gut and must change their dietary interests because of the inability to understand what happens inside of them. Fermented food and probiotics impair such disorders and restore the gut, which results in general health improvement.
The Best Food Diet Plan for Autistic Children
The analysis of different microelements in the human body and alternative treatments that can be offered to families with ASD or ADHD children proves the significance of dietary choices for health control. It is not enough for parents to provide their children with healthy food and avoid food allergies. Autism is a condition when any additional health problem or allergy can challenge the child and the family (Hendren et al., 2016). The control of the gut microbiota, the nervous system, and general health is a responsibility of a parent or any other caregiver, and if there is a chance to predict autism-related or allergic complications, it must be chosen.
In the medical field, the most famous food plans for ASD children from birth to 18 years are gluten- or casein-free diets and fermented products. Gluten- and casein-free diet will be a significant contribution to the safe development and growth of autistic children (Piwowarczyk et al., 2017). Probiotics in fermented food are helpful for children to predict infections and inflammations (Bell et al., 2018). Both options are effective for children to control their autism symptoms and predict behavioural changes.
There are no clearly defined attitudes towards the chosen food diet plans. Still, there are the supporters and promoters of gluten-free and fermented products. For example, such non-profit organisations like Autism Speaks (2017) and the Interactive Autism Network (2008) introduced the gluten-free diet as one of the common autism-focused diets for children. They recommended avoiding the usage of such products as rye or barley as they are the major sources of gluten.
Similar support is defined in terms of casein-free diets where the consumption of dairy products is rejected. Ly et al. (2017) hold the same positions despite the fact that the authors believe that the absence of such products can result in nutritional deficiencies (vitamin B, iron, or calcium). Piwowarczyk et al. (2017) and Valenta et al. (2015) investigated the benefits of these mixed diets and chose them for the body’s functional improvement. De Theije et al. (2014) promoted gluten-free and milk protein-free diets to control autistic behaviours and restore intestinal permeability. In many cases, the combination of both diets is appropriate to make sure ASD children avoid harmful products that increase disorder’s symptoms.
Fermentation processes also attract the attention of scientists in the field of medicine and health care offered to autistic patients. Fermented food contains probiotics that have a positive effect on the child’s intestinal system. The use of antibiotics or other harmful products is not always easy to control or prevent. Therefore, probiotics, along with fermented food, are consumed as a mediator between good and bad bacteria in the body. In their investigation, Bell et al. (2018) underlined a number of strengths of the chosen diet because it is not only a chance to restore the kids’ gut systems but an opportunity to avoid inflammations and negative food reactions.
In autistics children, food changes or removal of the already preferred food can be a real challenge. Fermented milk products with probiotics keep the balance in the gut, which is related to brain development and the stability of the nervous system (Zhu et al., 2017). Frye and Rossignol (2016) also discovered the benefits of probiotics in dealing with pathophysiological comorbidities that are observed in autistic children. All these examples explain the choice of gluten-/casein-free products and fermented food as the most famous dietary plans for ASD patients at an early age.
Conclusion
Such conditions as autism and food allergies are frequently observed in many children. These disorders are explained as a genetic predisposition, environmental factors, and the quality of life. Parents take any possible steps to predict health changes in their children, and as soon as a child is diagnosed with autism, appropriate care and treatment must be chosen. In this paper, the analysis of peer-reviewed articles, studies, and reports of non-profit organisations helps to reveal the most famous dietary plans for ASD and ADHD children. The connection between the gastrointestinal tract, the nervous system, and brain development cannot be ignored.
Therefore, the use of healthy products, supplements, and vitamins is an option for parents to stabilise the condition of a child. Although there is no definite cure to remove autism or food allergies from human life, multiple scientific efforts are directed to reduce symptoms and improve the quality of the child’s life. Gluten-free and casein-free diets are effective as well as fermented food that is rich in proteins. Dietary guidelines for children have to be constantly developed and improved in regards to children’s needs and parents’ expectations.
References
Autism Speaks. (2017). Autism and health: A special report by Autism Speaks. Web.
Autism Speaks. (n.d.). Autism facts and figures. Web.
Barnevik Olsson, M., Westerlund, J., Lundström, S., Giacobini, M., Fernell, E., & Gillberg, C. (2015). “Recovery” from the diagnosis of autism – And then? Neuropsychiatric Disease and Treatment, 11, 999-1005. Web.
Bell, V., Ferrão, J., & Fernandes, T. (2018). Fermented food guidelines for children. Journal of Pediatrics and Pediatric Medicine, 2(1), 1-4. Web.
De Theije, C. G. M., Wu, J., Koelink, P. J., Korte-Bouws, G. A. H., Borre, Y., Kas, M. J. H., … Kraneveld, A. D. (2014). Autistic-like behavioural and neurochemical changes in a mouse model of food allergy. Behavioural Brain Research, 261, 265–274. Web.
Fenech, M. (2012). Folate (vitamin B9) and vitamin B12 and their function in the maintenance of nuclear and mitochondrial genome integrity. Mutation Research, 733(1-2), 21–33. Web.
Food Allergy Research & Education. (n.d.). Facts and statistics. Web.
Frustaci, A., Neri, M., Cesario, A., Adams, J. B., Domenici, E., Dalla Bernardina, B., & Bonassi, S. (2012). Oxidative stress-related biomarkers in autism: Systematic review and meta-analyses. Free Radical Biology and Medicine, 52(10), 2128–2141. Web.
Frye, R. E., & Rossignol, D. A. (2016). Identification and treatment of Pathophysiological comorbidities of autism spectrum disorder to achieve optimal outcomes. Clinical Medicine Insights: Pediatrics, 10, 43-56. Web.
Frye, R. E., Melnyk, S., Fuchs, G., Reid, T., Jernigan, S., Pavliv, O.,… James, S. J. (2013). Effectiveness of methylcobalamin and folinic acid treatment on adaptive behavior in children with autistic disorder is related to glutathione redox status. Autism Research and Treatment, 2013. Web.
Hendren, R. L., James, S. J., Widjaja, F., Lawton, B., Rosenblatt, A., & Bent, S. (2016). Randomized, placebo-vontrolled trial of methyl B12 for children with autism. Journal of Child and Adolescent Psychopharmacology, 26(9), 774–783. Web.
Hus Bal, V., Fok, M., & Lord, C. (2017). Stability and change in ASD symptoms from childhood to young adulthood: Associations with spoken language development. Web.
Interactive Autism Network. (2008). IAN research findings: Special diets. Web.
Kerns, C. M., Newschaffer, C. J., & Berkowitz, S. J. (2015). Traumatic childhood events and autism spectrum disorder. Journal of Autism and Developmental Disorders, 45(11), 3475–3486. Web.
Ly, V., Bottelier, M., Hoekstra, P. J., Vasquez, A. A., Buitelaar, J. K., & Rommelse, N. N. (2017). Elimination diets’ efficacy and mechanisms in attention deficit hyperactivity disorder and autism spectrum disorder. European Child & Adolescent Psychiatry, 26(9), 1067-1079. Web.
Lyall, K., Croen, L., Daniels, J., Fallin, M. D., Ladd-Acosta, C., Lee, B. K., … Newschaffer, C. (2017). The changing epidemiology of autism spectrum disorders. Annual Review of Public Health, 38(1), 81–102. Web.
Moulton, E., Barton, M., Robins, D. L., Abrams, D. N., & Fein, D. (2016). Early characteristics of children with ASD who demonstrate optimal progress between age two and four. Journal of Autism and Developmental Disorders, 46(6), 2160–2173. Web.
National Health Service. (2019a). Overview: Food allergy. Web.
National Health Service. (2019b). What is autism? Web.
Orinstein, A., Tyson, K. E., Suh, J., Troyb, E., Helt, M., Rosenthal, M., … Fein, D. A. (2015). Psychiatric symptoms in youth with a history of autism and optimal outcome. Journal of Autism and Developmental Disorders, 45(11), 3703–3714. Web.
Pineles, S. L., Avery, R. A., & Liu, G. T. (2010). Vitamin B12 optic neuropathy in autism. Pediatrics, 126(4), 967-970.
Piwowarczyk, A., Horvath, A., Łukasik, J., Pisula, E., & Szajewska, H. (2017). Gluten- and casein-free diet and autism spectrum disorders in children: A systematic review. European Journal of Nutrition, 57(2), 433–440. Web.
Randall, M., Egberts, K. J., Samtani, A., Scholten, R. J., Hooft, L., Livingstone, N., … Williams, K. (2018). Diagnostic tests for autism spectrum disorder (ASD) in preschool children. Cochrane Database of Systematic Reviews, 2018(7). Web.
Solomon, M., Iosif, A. M., Libero, L., Li, D. D., Deprey, L., Ozonoff, S., … Amaral, D. G. (2017). IQ-based developmental phenotypes of ASD between ages 2 and 7 years and their correlates. Web.
Spain, D., Sin, J., Paliokosta, E., Furuta, M., Prunty, J. E., Chalder, T.,… Happé, F. G. (2017). Family therapy for autism spectrum disorders. Cochrane Database of Systematic Reviews, 5. Web.
Turke, P. W. (2017). Childhood food allergies: An evolutionary mismatch hypothesis. Evolution, Medicine, & Public Health, 2017(1), 154-160. Web.
Valenta, R., Hochwallner, H., Linhart, B., & Pahr, S. (2015). Food allergies: The basics. Gastroenterology, 148(6), 1120-1131. Web.
World Health Organization. (2018). Autism spectrum disorders. Web.
Xu, G., Snetselaar, L. G., Jing, J., Liu, B., Strathearn, L., & Bao, W. (2018). Association of food allergy and other allergic conditions with autism spectrum disorder in children. JAMA Network Open, 1(2). Web.
Zhang, Y., Hodgson, N. W., Trivedi, M. S., Abdolmaleky, H. M., Fournier, M., Cuenod, M., … Deth, R. C. (2016). Decreased brain levels of vitamin B12 in aging, autism and schizophrenia. PLoS One, 11(1). Web.
Zhu, X., Han, Y., Du, J., Liu, R., Jin, K., & Yi, W. (2017). Microbiota-gut-brain axis and the central nervous system. Oncotarget, 8(32), 53829-53832. Web.