There is no one-size-fits-all answer to the question of what causes ADHD and autism. However, there is growing evidence that suggests that eating habits and gut health play a role in the development of these conditions–mainly due to their impact on your microbiome as a whole. As we continue to explore the relationship between the gut microbiome, ADHD and autism, we'll discuss how integrative medicine can help identify underlying root causes. We will also look at the effects of certain foods upon ADHD symptoms, and how food additives and high sugar intake influences brain function.

For the 1 in 9 children who now live with ADHD very important questions remain about these figures. Are genetic changes at the root of this increase in the past decade? Or has our modern lifestyle begun to affect behavior in unexpected ways?

Learn more about conditions we treat: ADHD/ADD

What's responsible for the increase in ADHD and ASD?

Most conventional sources attribute genetics to the dramatic increase in attention deficit hyperactivity disorder (ADHD) and autism spectrum disorders (ASDs) in the past decades, but other than that—there aren't any real known causes.

Others go as far to say that eating habits and a child's diet have nothing to do with autism spectrum disorders or ADHD symptoms. But this approach is not aligned with what current research suggests. On the contrary, current research tells us two things:

Genetic changes occur too slowly to be the sole factor responsible for ASDs and ADHD.
That there are some environmental factors that are contributing to this increase in ADHD or ASDs.

Environmental factors vs. genetics

Because the prevalence of ADHD has increased almost 50 percent in the last 10 years (with ASDs not far behind), this suggests that environmental factors like diet—and not just genetics—are a major contributing factor, though genes do certainly play a role in predisposition (1).

First, while ADHD and autism spectrum disorders are not the same thing, they do share some characteristics and overlapping symptoms. What they have in common are changes in typical brain function, and in certain mechanisms responsible (2).

For example, changes in the neurotransmitters dopamine and serotonin have both been implicated in the development and mechanisms of ASDs and can affect ADHD symptoms. Current studies show a link between the production, function, or transport of certain neurotransmitters and this may contribute to the onset of symptoms associated with neurodivergent disorders (3).

When we examine autism spectrum disorders or ADHD it's also important to remember that research is constantly evolving. As recently as 2011, the FDA stated that synthetic color additives had no adverse effects on cognition (4). However, research has since shown that they can worsen ADHD symptoms, and that some children are more sensitive than others to their effects (5).

Read: Exploring the Link Between ADHD and Anxiety

Brain function and your gut—ADHD and ASDs

Many lines of scientific research suggest that Autism Spectrum Disorders (ASDs) may be linked with changes in the body's internal ecosystem—that is, the microbiome.

Changes in our microbiome are believed to be due to a variety of factors relating to the developed world: decreased exposure to beneficial bacteria, dietary changes, and an overuse of antibiotics. The microbiome then goes on to alter the immune system and metabolic function—which then both influence the expression of certain genes.

If these changes occur during critical developmental windows, it can alter the trajectory of brain development, as well as brain function.

The collection of these changes may converge to trigger or exacerbate the formation of an ASD. Authors of one meta-analysis explain this process with three points (6):

Biome depletion
Environmental stimulus
Genetic or epigenetic predisposition

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Does ‘biome depletion’ cause ADHD?

The first factor that researchers believe alters the gut microbiome is what’s referred to as “biome depletion”. This is a loss of certain gut bacteria that has been suggested to contribute to not only autoimmune diseases but also conditions like autism, and possibly ADHD.

The ‘biome depletion hypothesis’ suggests that beneficial gut bacteria have co-evolved with humans over hundreds of thousands of years to regulate and stabilize immune function. And that our lifestyle and dietary habits are what’s responsible for the reduced diversity in these symbiotic gut microbes.

Things like an ultra-hygienic environment, increased antibiotic usage, and lack of exposure to beneficial microbes disrupts the microbiome in a way that results in a lack of immune competence. And that, in turn, increases the risk of autoimmune disease, food sensitivities, autism spectrum disorder, ADHD, and a host of other problems.

Changes in gut bacteria are also linked to an increase in leaky gut, which research suggests is a key trigger for food sensitivities. People with ADHD are also more likely to experience food sensitivities than those without (7).

Diet and other environmental factors do play a role in ADHD and ASDs

The second factor contributing to the development of these disorders is an environmental trigger. This includes a potentially very long list of diet and lifestyle factors, which may be:

Poor diet (Standard American Diet, or a lack of healthy foods)
High consumption of refined and processed foods (including food additives, sugar, and artificial colors)
Increased antibiotic use
Vitamin D deficiency
Low intake of essential fatty acids

Children with ADHD have been shown to have a higher deficiency in essential fatty acids (such as omega-3s) despite consuming similar amounts of EFAs as those without ADHD (8). Similarly, supplementation with high-dose omega-3 has been shown to help manage ADHD symptoms in both children and adults.

Related: Brain Health, ADHD, and Omega-3s

A genetic predisposition to ASD or ADHD

Obviously, not all kids with a less-than-healthy diet or who were exposed to (and needed) antibiotics at a young age have ADHD or ASDs. So why do some children have this experience and other kids do not?

This is where genetics and epigenetics come in.

You may have heard the role of epigenetics explained like this: Adding eggs, butter, and flour to a bowl doesn’t automatically produce a cake. But if you combine them in a certain way and perform the necessary actions, the result is a cake. Your genes in this case provide the ingredients, but your environment and personal choices control the outcome to a large extent.

Epigenetics is the study of how your behaviors and environment influences which genes get expressed, and which do not. For some people, a combination of ingredients (genes), paired with an environmental trigger, may result in the development of ADHD or ASDs.

How does Sugar affect ADHD symptoms?

The role of diet in ADHD is a complex one. While some studies have found no correlation with sugar intake and ‘hyperactivity’, others have shown that the more sugar a child with ADHD consumes, the more restless and destructive they become (9).

So, while sugar itself isn’t likely to cause ADHD symptoms, it does appear that it can worsen them in children who already struggle with attention issues.

There is also some evidence that certain food additives can contribute to hyperactive behavior, although again, it’s not clear if this is cause and effect or just an association.

GABA/Glutamate Imbalance

A diet high in refined foods and low in essential minerals can contribute to an imbalance in neurotransmitters, such as GABA and glutamate.

GABA, or gamma aminobutyric acid, is an amino acid and neurotransmitter that calms the brain, while glutamate is more excitatory in nature, stimulating the brain and sometimes putting it in overdrive.

Low GABA levels are associated with ADHD (10). Low GABA is usually accompanied by inattention while high glutamate levels can lead to aggression and impulsivity. GABA, like serotonin, is primarily manufactured in the gut.

Artificial colors & food additives

Red dye #40 is a synthetic food dye made from byproducts of petroleum. It is linked to certain ADHD symptoms, such as hyperactivity, and may cause neurological effects in children (11). While small amounts are generally considered safe for consumption, some children may be more sensitive to its effects than others.

Will restoring gut microbiota cure ADHD symptoms and ASD?

The simple answer is that there is no ‘cure’ for ADHD or ASD, and even if we could restore the gut microbiota, it’s unlikely that these conditions would be completely cured.

We do know that the gut microbiota plays a role in both ADHD and ASD, but we don’t yet know if restoring the microbiota would completely reverse these conditions or help alleviate some of the symptoms.

It is possible that restoring the gut microbiota, improving the diet, and optimizing overall health could help alleviate some of the symptoms of these conditions, and this is something that warrants further investigation.

The bottom line on diet and ADHD

So what does all this mean? Well, first of all, it means that there is no singular cause of ADHD or autism spectrum disorders.

These are complex disorders with a variety of possible underlying causes. And that’s why integrative medicine approaches like functional medicine are so important.

Functional medicine is all about identifying and addressing the underlying root causes of disease, rather than just treating the symptoms. In the case of ADHD and autism spectrum disorder, some of the underlying root causes may include things like:

Microbiota depletion
Poor diet
Nutrient deficiencies
Exposure to toxins

By addressing these underlying causes, we can often improve symptoms. If you or someone you know is struggling with ADHD or autism spectrum disorder, there is hope. Contact a patient care coordinator today to learn more about how we can help.

Working with an integrative provider

The gut microbiome has been implicated in a range of chronic diseases, including autism spectrum disorders and ADHD. While the research is still emerging, it’s clear that diet and lifestyle can play a role in shaping the gut microbiome, and thus brain function. To promote a healthy gut microbiome, eat a healthy diet of vegetables, fruits, and minimally processed grains; drink plenty of water; get regular exercise; and reduce stress in your life. It’s also important to avoid antibiotic overuse and exposure to environmental toxins.

If you are struggling with symptoms related to ADHD or an ASD, it’s important to consult with a qualified integrative practitioner who can help you develop a treatment plan that works for you.

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About
the author

CentreSpring MD, formerly known as Atlanta Center for Holistic and Integrative Medicine, provides the best medical care by using an integrative approach to find a patient’s centre—their core—empowering them to spring forth into health.

Blog Reviewed By:

Dr. Taz Bhatia, M.D.

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ADHD and Autism: The Role of Diet and Gut Health