Updated on January 3, 2023
- Research suggests that food plays a critical role in the development of autism and in the escalation of autism symptoms.
- Food-related issues, such as selective eating and nutritional deficiencies, are often manifestations of autism.
- Of the dietary therapies proposed to manage autism symptoms, those that support the gut microbiome via targeted supplementation are considered particularly promising.
Within both the research and the clinical communities, the relationship between autism spectrum disorder (ASD) and diet has long been a topic of discussion. However, understanding the complex relationship between autism and food continues to be an ongoing challenge. This is largely because food can play a role in each of three distinct areas: the development of autism, the manifestation of symptoms, and addressing the condition. When considering the relationship between autism and food from each of these three perspectives, it is important to examine the existing research and what it can mean for the future of autism therapies.
Food as a Contributing Factor to the Development of Autism
There is broad consensus within the research community that autism is caused by a wide range of factors, including both genetic characteristics and environmental influences. Most scientists also agree that the pathogenesis of autism begins during prenatal development. This idea has led some researchers to hypothesize that the mother’s nutritional status might be among the environmental causes of autism that interact with genetic factors to cause autism’s development. Indeed, multiple studies have established strong correlations between diet-related health conditions in the mother and a higher risk of autism in the child. For instance, both type 2 diabetes and gestational diabetes are associated with a higher risk of autism. In addition, if the mother meets the standards for obesity, then the risk of autism increases by 21.5 percent, and if the mother has hypertension, then the risk of autism in the child rises by 14.3 percent.
In 2017, a researcher at UC Davis published a paper proposing a mechanism through which a mother’s diet-related health conditions might facilitate the development of autism. Based on a review of the latest research in the field, the researcher suggests that these conditions are associated with a lower intake of several key micronutrients that might be involved in the etiology of autism: zinc, copper, iron, and vitamin B9. In combination with genetic risk factors, an insufficient intake of these nutrients might contribute to disruptions in fetal brain development that lead to autism. Although future research is needed to conclusively establish a causal relationship between maternal nutritional status and autism, it is clear that the mother’s relationship with food before and during pregnancy is associated with the development of autism.
It is important to note that pregnant mothers who have one of these food-related health conditions can still take action — making strategic dietary decisions that target specific micronutrients — to address the risk of autism for the child. Studies in animal models suggest that supplements with certain micronutrients might address autism risk. In the future, clinical trials in humans might make it possible to identify the most effective food and nutritional supplement choices for expectant mothers who are concerned about autism.
Food-Related Issues as a Manifestation of Autism
Although the discussion of food as a potential cause of autism remains primarily confined to the research community, many patients and families experience a concrete connection between food and autism on a daily basis. Put simply, children with autism are significantly more likely to be “selective” or “picky” eaters. According to one estimate, one-fourth of healthy children are picky eaters, whereas about 80 percent of children with autism demonstrate selective eating tendencies, often refusing to eat (or even try) whole categories of foods. In the most serious cases, an autistic child might limit their diet to as few as five foods.
One of the proposed explanations for selective eating among autistic children is their heightened sensory sensitivity. According to some estimates, about 90 percent of children with autism process tactile, olfactory, visual, and auditory information differently than normally developing children. Based on these statistics, it should come as no surprise that preferences regarding the taste, texture, smell, and even appearance of food are evident in children with autism.
Unsurprisingly, studies also show that selective eating issues in children with autism can lead to deficiencies in important micronutrients—especially among children with the most restrictive diets. Although specific nutritional deficiencies are likely to depend largely on a child’s individual food restrictions, a broad study of more than 250 autistic children from five different U.S. states highlighted insufficient consumption of vitamin A, vitamin C, zinc, phosphorus, fiber, choline, calcium, vitamin D, and potassium. Although the commonness of inadequate intake is just as high among normally-developing children as autistic children for some of these nutrients, the effects on autistic children might be more significant. For instance, evidence suggests that certain nutrients are less readily absorbed by autistic children. As a result, the problem can quickly escalate from inadequate intake to measurable nutrient deficiency.
A possible explanation for why certain nutrients are less readily absorbed in autistic children is the difference between the gut microbiome in children with autism and their healthy counterparts. Bacteria in the gut play a key role in nutrient absorption, and studies in both human and animal models suggest that the bacterial composition of the gut is different for children with autism. Although there are not yet results from clinical trials, modifying the gut microbiome in children with autism to optimize absorption and address gastrointestinal issues is being considered as a potential therapy.
Food as a Contributor to the Escalation of Autism Symptoms
For children with autism, food selectivity can also exacerbate other symptoms. Deficiencies in multiple nutrients, including vitamin B12, vitamin D, and folic acid, have all been associated with autism etiology and the core symptoms of the disorder. Moreover, it is widely recognized within the research and clinical communities that the gut microbiome is impacted by food choices—and the health of the gut microbiome is directly related to both gastrointestinal and neurological symptoms of autism. For instance, disruptions in the gut microbiome can affect gut motility, which is a common symptom of autism. Also, in patients with Leaky Gut syndrome (which is also common among patients with autism), toxins from the microbiome can enter the bloodstream and impact the brain, potentially contributing to the neurological symptoms of autism. Because repetitive behaviors—such as selective eating—are among these neurological symptoms, abnormal food behaviors in autistic children might even be driving a vicious cycle: the more a child restricts nutrients, the more their internal neurological processes will support a tendency toward restriction.
There is also preliminary evidence that consuming certain types of foods directly exacerbate symptoms of autism. For example, some studies indicate that dietary gluten and casein are not properly digested in the gut of individuals with autism. Not only can the resulting peptides interfere with regular bowel motility, they can also directly affect brain functioning. In patients with “leaky gut”—a condition commonly associated with autism—partially-digested peptides can cross the intestinal barrier and build up the brain, where they can have an opioid-like effect associated with some of autism’s core symptoms.
Food as a Possible Therapy for Children with Autism
Because of the associations between eating behaviors, nutritional status, and autism, a wide range of food-related therapies have been proposed by both researchers and practitioners. Some of the most popular are elimination diets, like gluten-free, casein-free, and lactose-free diets. Other dietary strategies emphasize the importance of eating more probiotic-rich foods that support the health of the gut microbiome. Although small-scale studies have examined the efficacy of specific diets for individuals with autism, the results are mixed. Given that selective eating patterns vary widely, it is little surprise that no single diet has been identified as the best option.
Still, some clinicians can recommend dietary strategies based on an individualized evaluation of their patient’s symptoms and needs. Improving the health of the gut microbiome can be a major goal of these dietary strategies. As previously mentioned, studies suggest that the bacterial composition of the gut is tied to both gastrointestinal and neurological symptoms, so a physician might recommend nutritional changes that focus specifically on the gut microbiome.
If an autistic child is not getting the nutrition they need from food, then another option is to support micronutrient intake through supplementation. Taking supplements optimized for bioavailability can be helpful for a child who struggles with the sensory processing of a normal, balanced diet. Although research is still in the early stages, studies on supplements like butyric acid, vitamin B12, and folinic acid offer preliminary evidence of addressing behavioral symptoms in children with autism.
Clearly, the relationship between autism and food is complicated. In pregnant mothers, nutritional status can affect a child’s risk for autism. During childhood and beyond, abnormal food behaviors can manifest as a symptom of autism, which can exacerbate other symptoms by affecting the child’s neurological and gastrointestinal functioning. At the same time, the relationship between autism and food presents opportunities for dietary interventions that might help symptoms of autism. This possibility is opening up exciting avenues for research into nutritional supplementation therapies for children with autism.
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