Nutritional therapy for autistic children - the rationale?

In medicine, it’s convenient when there is one ‘causal’ factor that can be dealt with, however, as we know, there is nothing convenient about ASD. There are many genetic and environmental factors that have been identified, with some being tentatively and others more firmly placed along the causal pathway.


These causal factors may be common in many but also often vary, and the ASD phenotype itself has enormous heterogeneity. We've all heard the phrase: 'When you've met one autistic person, you've met one autistic person.' This mantra is as vital for nutrient therapy as it is for any other intervention.

Genetic predisposition - Researchers have identified over 800 genes associated with ASD. We know neurodiversity runs in families (heritability estimates of 50–83%), but until recently, we didn’t know why the prevalence was increasing at such a rate. 

It’s clear now that it’s not simply a case of a greater awareness leading to more diagnoses. Another contributory factor is the higher burden of environmental triggers causing changes to the genes themselves (mutations) and to their expression (epigenetics). Some of these changes are reversible, while others aren’t.

Environment - The field of epigenetics is increasingly showing us how our environment can alter the expression and function of our genes, not only during preconception but post-conception and throughout our life course. ASD children show a much greater genetic vulnerability to toxins and much higher levels of oxidative stress than neurotypicals. This directly contributes to body and brain inflammation, and also results in more genes being inappropriately switched on or off, messing with the child's biological systems and adding proverbial fuel to the physiological fire.

This can leave ASD children progressively more sensitive to their environment, and even more vulnerable to inflammation and oxidative stress - a vicious circle sometimes leading to severe and sudden worsening of symptoms or regression, during periods of nutritional vulnerability and high environmental stress. The associated brain inflammation can worsen anxiety, depression, OCD, sensory processing disorder, sleep disorders, and behavioural problems. 

Diet and other environmental exposures can impact our ASD children’s genes from pre-conception all the way throughout their lives, with the brain development window not closing until they are around 25 years old. We can’t change environmental insults already received, but we can modify our child’s environment, and support their physiological systems with nutrient therapy, to reverse toxic damage where possible (and it is possible), and prevent further damage from occurring.

How does brain and body inflammation contribute to anxiety, depression, sleep disorders, etc? 

We’ve known for some time that the brains of ASD children (and adults) experience altered neurotransmitter levels, receptor function, and metabolic pathway disturbances. The neurotransmitters involved include serotonin and melatonin, dopamine and norepinephrine, glutamate, GABA, and even histamine (yes histamine can act as a neurotransmitter).

Inflammation as a cause of mental health conditions is very much against the old medical model of mental health where the brain and body were believed to be largely immunologically separate. However, it is now an established belief among many leaders of research in psychiatry that cytokines (and potentially other inflammatory mediators) released by our immune system during an inflammatory response, cross the blood-brain barrier, enter the brain and trigger the brain’s immune cells (microglia) to release cytokines in the brain. This can damage neurons and alter the function of neurotransmitters, triggering or worsening mental health disorders, such as anxiety, depression, OCD, also sensory processing problems, motor skill impairment, and sleep disorders.

This causal mechanistic theory has been reinforced by research showing that interventions to reduce or block this inflammation cascade, or remove the trigger(s) of inflammation, causes mental health symptoms to subside.

What triggers inflammation in ASD?

Gut dysbiosis 

The gut is one of the body's main 'gates' to the environment and its defences against toxins are impaired in ASD.

A healthy gut has a mucin layer that protects the one-cell-thick lining and is home to a balanced ecosystem of microbes (bacteria, fungi/yeasts, viruses) with just the bacteria alone outnumbering our total human body cells 10 to one. The microbiota, directly and indirectly, interacts with the immune system, the brain, and the endocrine system. A healthy gut breaks down toxins, kills invading pathogens, and optimises the breakdown and transport of nutrients from our diet.  

In ASD (regardless of the presence of gastrointestinal symptoms), the gut lining is often inflamed, the mucin layer is degraded, the microbiota is frequently pathogenic and there are often low-level infections i.e. yeast infection: candida. This dysbiosis leads to increased gut permeability and increases the immune system’s exposure to food proteins, often triggering/exacerbating food allergies and increasing oxidative stress within the body. Repeated triggers of the immune system can eventually result in the development of certain autoimmune conditions.

In ASD, toxins either ingested from our diet (herbicides, pesticides, heavy metals etc) or produced by pathogenic microbes, aren’t broken down and/or excreted effectively in the gut, or the liver. They accumulate in the body, trigger inflammation and oxidative stress, damage mitochondria and disrupt the methylation cycle, triggering further epigenetic changes, causing neurotoxicity and neuroinflammation in the brain, and worsening conditions associated with altered brain neurotransmitter function. 

In addition, the ASD population has a much greater risk of suffering from GI disorders such as IBS and chronic constipation, which worsen inflammation, cause further nutrient deficits and increase the toxic load. 

Toxin accumulation  

ASD children are more vulnerable to toxins entering their blood due to increased gut permeability and reduced detoxification capacity within the gut itself.

ASD children also often have impaired liver detoxification and a more permeable blood-brain barrier than neurotypicals, which can result in toxin accumulation in the body and brain. 

The reduced liver detoxification capacity is due to genetic polymorphisms in phase I and II liver enzymes such as cytochrome p450 and Glutathione-S-Transferase. Single Nucleotide Polymorphisms, SNPs  (pronounced ‘snips’) occur much more frequently in these enzymes in ASD. A SNP is essentially a mis-programming in the building of a protein (usually enzymes) so that one amino acid is placed where another one should be. Often this has no effect on the enzyme’s function but other times, especially if it occurs in an important location on an enzyme, it can significantly reduce (or sometimes increase) the function of the enzyme, usually somewhere between 20-80%.

In the genes identified to be associated with ASD, 47 have been found to encode for detoxification enzymes and 30 encode for proteins involved in physiological barrier function like the blood-brain barrier, explaining the predisposition in ASD for toxins to enter the brain. Nutrient therapies can be used to enhance the function of enzymes made sluggish by polymorphisms, and also to help restore the integrity of the gut and the blood-brain barrier. 

So, where do we start?

Clinical Nutritionists should take a broad and thorough patient history and assessment which should flag any undiagnosed medical conditions, for example, IBD, celiac disease, eating disorders, or undiagnosed mental health disorders, and refer immediately for a diagnosis.

Nutritional therapy itself is best focussed upstream, identifying and removing any causes of oxidative stress and inflammation in the child. Triggers could be due to a number of factors, such as low-grade gastrointestinal infections or dysbiosis, toxins from the diet and environment, endogenous toxins, or food allergies or sensitivities.

Once the triggers have been identified and removed where possible, any residual inflammation and oxidative stress should be tempered with targeted nutrient therapy. This can encompass a wide range of potential interventions from supporting liver detoxification, restoring gut health and physiological membrane integrity, supporting immune regulation, providing cofactors for ‘sluggish’ biochemical pathways in the body and brain, and most crucially, determining an optimal diet to suit the child and their physical and psychological needs, whilst placing minimum burden on the family. 

It’s important nutrient therapies and diet interventions are tailored to the individual; there are many common physiological and biochemical imbalances in ASD, yet each genotype (the genes our child has) and phenotype (how they are expressed in their body) are entirely unique, and should be treated as such. The best approach is personalised, led by a specialist, and tailored to signs, symptoms and where appropriate, laboratory results, and always backed by the most robust clinical evidence available. 

We are specialists in nutrition therapy in ASD children, so please do get in touch if you would like to find out more. 

The views expressed in this article are those of the author. All articles published on Nutritionist Resource are reviewed by our editorial team.

Share this article with a friend
Tunbridge Wells TN1 & London N1
Written by Haley Hill, MSc (Clinical Nutrition), BSc(Hons) (Pharmacy), PgDip, AfN
Tunbridge Wells TN1 & London N1

Haley is a registered Clinical Nutritionist (AfN) with a MSc (distinction) in Clinical Nutrition, and a BSc (Hons) & PGDip in Pharmacy and Clinical Pharmacy. She has held senior clinical roles within NHS teaching hospitals and specialist clinical rotations within the HCA hospital group, The Maudsley and The Priory.

Show comments

Find the right nutritionist for you

All nutrition professionals are verified

All nutrition professionals are verified