Nutritional Deficiencies in Autism

Nutritinal deficiencies -featured

All contents of this resource were created for informational purposes only and are not intended to be a substitute for professional advice, diagnosis, or treatment. Always seek the advice of your physician, therapist, or other qualified health providers with any questions or concerns you may have.

There are numerous circumstances in which our kids diagnosed with autism have nutritional deficiencies. This can be due to restricted eating habits, malabsorption issues in a compromised gastrointestinal tract, autoimmunity, or even genetic abnormalities. No matter the reason, this can have serious impacts on health. In addition, nutritional deficiencies can actually contribute to autism symptoms! Therefore, we will explore the symptoms of some of the most commonly missing vitamins and minerals.

This TACA article will cover:

  • Why do we see nutrient deficiencies in autism?
  • Consequences of nutrient deficiencies 
  • Testing for nutrient deficiencies 
  • Water-Soluble Vitamins
  • Fat-soluble vitamins
  • Minerals
  • Lipids
  • Amino Acids
Graphic illustrating 'Nutritional Deficiencies' in the center with arrows linking it to various causes. Around it are text bubbles labeled 'Picky, Restricted Eating Habits,' 'Malabsorption,' 'Autoimmunity,' and 'Genetics,' each contributing to the central theme of nutritional deficiencies.

Reasons for nutrient deficiencies in kids diagnosed with autism

There are numerous reasons for nutrient deficiencies in kids diagnosed with autism. 

Picky, restricted eating habits.

This 2020 research review of 63 published articles explains that severe nutrient deficiencies of vitamin A, thiamine (B1), vitamin B12, vitamin C, and vitamin D were found in individuals with autism due to their restricted eating. Additionally, this study of kids ages 0-17 with avoidant/restrictive food intake disorder (ARFID) met only 20%-30% of the recommended intake for most vitamins and minerals, with significantly lower intake of vitamin B1, B2, C, K, zinc, iron, and potassium. 

Malabsorption in the gut

Although a healthy diet is always first priority, the compromised gastrointestinal tracts of autism patients can cause nutrient malabsorption issues. Malabsorption can occur for many reasons including Celiac disease, a lack of gastric acid, Small Intestinal Bacterial Overgrowth (SIBO), a lack of digestive enzymes, or a parasitic infection. When these GI issues are present, the body cannot absorb vitamins and minerals as it should. This means that your child could have a very healthy diet but still be very deficient in micronutrients. 

Autoimmunity in the form of autoantibodies blocking nutrient receptors.

Autoimmunity can cause poor folate absorption. This occurs when folate receptor autoantibodies can block the absorption of folate. As a result, levels of folate in the brain are decreased. Learn more in this TACA article on Cerebral Folate Deficiency

An inability to use the form of the vitamin eaten or taken due to particular genetics (SNPs)

Genetic polymorphisms can affect the body’s ability to absorb nutrients. An example of this is the VDR polymorphism, which makes it hard for the body to absorb and use Vitamin D. Likewise, this study showed that some kids with autism had high levels of B6 in their blood, but low levels of the bioavailable form of B6, p5p. They may be unable to convert vitamins to their bioavailable form. 

Chart presenting a list of vitamins and minerals, their corresponding deficiency diseases, and the manifestations of these diseases.

Consequences of Nutrient Deficiencies

There is research showing more kids are being diagnosed with disorders such as Scurvy (lack of Vitamin C) and Beriberi (lack of B1). Doctors have not seen diseases as a result of nutrient deficiencies in many years because of wide-spread access to a variety of foods. Therefore, doctors may not even recognize it when seeing it. However, case studies are showing that some kids with autism are being diagnosed with serious deficiency diseases. 

This 2022 publication of critical vitamin deficiencies in autism showed: 

  • A patient with Beri-Beri as a result of B1 deficiency presented with cardiac arrest and severe neurological problems. Unfortunately, rapid vitamin supplementation did not stop the progression of the disease. 
  • Several children with autism had a critical level of thiamine (B1) deficiency.
  • Another patient with scurvy as a result of vitamin C deficiency had symptoms of leg pain and limping. He recovered with IV Vitamin C and tube feeding.

How to Determine if your Child has Deficiencies 

There is lab testing that can reveal deficiencies. Additionally, you can look for symptoms.  

*Please note that if lab testing shows a deficiency, therapeutic doses may be required and should be accomplished under the care of a functional medicine practitioner.
There is a difference between a standard dose and a therapeutic dose.

  • A standard dose or RDA (Recommended Dietary Allowance) is the amount of a vitamin or mineral needed for the average healthy person to stay well.
  • By contrast, therapeutic doses are higher doses given to achieve a desired outcome. These doses require a functional medicine provider for guidance.

Most vitamins and minerals can be checked with regular bloodwork through LabCorp or Quest Labs. They are individually ordered. However, most insurance companies will not cover these tests unless there is a documented need to test for them, and the correct insurance billing code is provided. Lastly, it is important to remember that even if a blood test does not show a deficiency, that does not mean that the vitamin or mineral is getting to where it needs to go in the body. For example, you can have perfect serum folate levels but low folate levels in the brain.

Additionally, there are specialty labs that look at a wide variety of micronutrients:

Water-Soluble Vitamins

Water-soluble vitamins are easily absorbed. Excess water-soluble vitamins are excreted in the urine. 

Vitamin B1 (Thiamine)

Thiamine plays an important role in the metabolism of fats, carbohydrates, and protein. Therefore, it is important for mitochondrial function.

The bioavailable forms of B1 are alliathiamine, lipothiamine, benfonthiamine.

Often seen in conjunction with Vitamin B1 deficiency:

Vitamin B2 (Riboflavin)

Riboflavin is also important to the metabolism of carbohydrates, fat, and protein. It is also needed to activate B6 and B9.
Often, if you get a fishy smell from taking L-carnitine, B2 will resolve that issue.

The bioavailable form of B2 is r5p.

Often seen in conjunction with Vitamin B2 deficiency:

Vitamin B3 (Niacin)

Niacin is important for cell metabolism and is the only vitamin that releases growth hormones. It also stimulates hydrochloric acid in the stomach to ensure proper digestion. 

Niacin is known as “nature’s valium” because it is very calming.

The best form of niacin is niacinamide because it will not cause flushing.

Often seen in conjunction with Vitamin B3 deficiency:

Vitamin B5 (Pantothenic acid)

B5 is called the anti-stress vitamin because it activates the adrenal glands to produce cortisol.

The bioavailable form of B5 is Coenzyme A.

Often seen in conjunction with Vitamin B5 deficiency:

Vitamin B6 (Pyridoxine)

B6 is involved in energy, amino acid, carbohydrate, lipid, and hormone metabolism. Additionally, B6 works to make neurotransmitters and is responsible for nerve function.

The active form of B6 is p5p.

Often seen in conjunction with Vitamin B6 deficiency:

Vitamin B9 (Folate)

Folate is brain food. It is needed to make red blood cells, for energy production, and is important for proper cell division and replication. 
There is also research showing that many kids diagnosed with autism have autoantibodies that block folate from entering the brain. See more information on that topic in TACA’s website article titled “Cerebral Folate Deficiency in Autism

The most bioavailable forms of B9 are folinic acid and 5MTHF.
Folic acid should be avoided as it is oxidized and difficult for most people to convert to a usable form. 

Often seen in conjunction with Vitamin B9 deficiency:

Vitamin B12 (cobalamin)

B12 is a red vitamin needed to make red blood cells, protect the nervous system, and metabolize carbohydrates, fats, and proteins,

Methyl B12 not only supports methylation but has also been found to help many kids with autism. Learn more about Methyl B12 for Autism here

Active forms of B12 are Methylcobalamin (MB12) and Adenosylcobalamin (AB12).

Often seen in conjunction with Vitamin B12 deficiency:

Vitamin C (ascorbic acid)

Vitamin C is a powerful antioxidant; therefore, it is important for immunity. It is needed to help heal wounds and assist iron absorption. 

The body does not produce or store Vitamin C, so sources of Vitamin C MUST be eaten regularly to avoid a deficiency.  

It is important to know that Vitamin C supplementation is contraindicated with kidney disease, high oxalates, and hemochromatosis.

Also note that Vitamin C is derived from corn, in case there is a corn sensitivity. 

Often seen in conjunction with Vitamin C deficiency: 

Fat-soluble vitamins 

Fat-soluble vitamins must be taken with a fat to be absorbed. They can accumulate in the liver; therefore, monitoring levels with blood testing is critical. 

Vitamin A

Vitamin A is important to fight off illness and infections. Additionally, it is needed for proper vision, growth, and development

The retinol-binding protein that transports vitamin A needs zinc. Therefore, if there is a zinc deficiency, vitamin A function is usually impaired. 
Zinc converts retinol to retinal, which is the form of vitamin A needed for rods in the eyes.  

Micellized Vitamin A is a water-soluble form of Vitamin A, which is well absorbed. 

Often seen in conjunction with Vitamin A deficiency:

Vitamin D

Vitamin D is needed to help the body absorb calcium and fight off illness and infection. The majority of Vitamin D is made in the skin after being exposed to sunshine. However, despite plenty of sunshine it, is still possible that some kids cannot convert sunshine to Vitamin D effectively.

This 2020 study of 1529 patients with ASD, ages 3 to 18 years, showed Vitamin D deficiency or insufficiency was found in approximately 95% of all patients.

Vitamin D3 is best for supplementation.

Often seen in conjunction with Vitamin D deficiency:

Vitamin E

Vitamin E is an antioxidant that prevents cell damage by inhibiting the oxidation of fats. It also helps nerve function, muscle health, and cholesterol metabolism.

D-alpha-tocopherol or mixed natural tocopherols are the most effective.

Often seen in conjunction with Vitamin E deficiency:

Vitamin K

Vitamin K is needed for blood clotting and bone formation and helps the bone absorb calcium.

The best form is MK-7 (K2)

Often seen in conjunction with Vitamin K deficiency:


Minerals are important for bones, teeth, hormone production, muscles, and brain and nervous system health.


Magnesium is a critical mineral needed for hundreds of metabolic processes in the body. It is needed for energy production, for the uptake of calcium and potassium, for hormone production, and more. 

This study from 2020 showed that kids with autism and ADHD had lower magnesium in their hair and excreted too much magnesium in their urine. For this reason, hair and urinary magnesium levels were considered significant predictors of neurodevelopmental disorders.

Different forms of magnesium have different functions. 

  • Magnesium Citrate – for constipation
  • Magnesium Oxide – for constipation 
  • Magnesium Glycinate – for calming and sleep
  • Magnesium L-Threonate – for cognition 
  • Magnesium Sulfate (used as Epsom Salt in baths) – for calming
  • Magnesium Taurate – for nerve and muscle function 
  • Magnesium Malate – for energy production and detoxification 
  • Magnesium Chloride – to increase low stomach acid, boost energy, and relax muscles 

Common symptoms of deficiency are:


Iron is needed for the production of hemoglobin which takes oxygen from the lungs to the tissues. It is important for growth, a healthy immune system, and energy production. 


  • Your doctor must test your child’s iron level before supplementation because too much iron is dangerous.
  • A hemoglobin test is not enough. You need an iron panel and ferritin to know exact iron levels.  

Common symptoms of deficiency are:


Every human cell contains zinc. It is very important to immune function and proper growth. Additionally, zinc is needed for reproductive health, energy metabolism, proper sense of taste and smell, and to fight the formation of free radicals. 

Note about zinc & copper:

Taking zinc is known for upsetting the stomach, so make sure to take it with food. 
In addition, zinc can lower cortisol levels; therefore, it is better to take it in the evening since it is ideal for cortisol to be lower before bedtime. 

Zinc Picolinate tends to be the zinc form of choice, especially when using zinc to treat picky eating. 

Common symptoms of zinc deficiency are:


Lipids are fats that control what goes in and out of cells. They also help absorb vitamins and make hormones. 

Omega 3 Fatty Acids (EPA & DHA)

Omega 3s keep cell walls soft and not rigid. Sixty percent of the brain is fat; therefore, healthy fats are extremely important to brain health.

The body cannot make Omega 3 fatty acids, so they are considered “essential”.

The most bioavailable forms of Omega 3 are found in fish. For this reason, it is referred to as fish oil. Therefore, if you do not eat fish, you likely need a supplement. Make sure your supplement is third-party tested for mercury toxicity. Look for brands that are molecularly distilled.

The three main omega-3 fatty acids are:

  • Alpha-linolenic acid (ALA) – This is found in plants and can be converted to EPA & DHA to be used by the body BUT studies show only a very low percentage of Alpha-linolenic acid is actually converted to a usable form.
  • Eicosapentaenoic acid (EPA) – EPA is an anti-inflammatory.
  • Docosahexaenoic acid (DHA) – DHA is known to help with cognition

Common symptoms of Omega 3 fatty acid deficiency are:

Coenzyme Q10 (Ubiquinone)

CoQ10 is critical to energy production. In fact, ubiquinol is the most important nutrient for mitochondrial dysfunction which is so common in autism. For this reason, it is very important for neurological function, cognition, immune function, and circulation. It also inhibits histamine, so it can be beneficial for allergies. 

CoQ10 is oil soluble and best when taken with fatty food or healthy oil for best absorption.

The most bioavailable form of CoQ10 is ubiquinol.

Common symptoms of CoQ10 deficiency are:

Amino Acids

Amino acids are the building blocks of proteins.


Carnitine carries fat into the cell so it can be used for energy. Therefore, if you have difficulty with fatty acid oxidation (or breaking down fatty acids to more useable forms to then be converted to energy), then carnitine is needed. Remember that it only helps to eat healthy fats if the body can use them. For these reasons, L-carnitine is a very important mitochondrial support.

The body can make its own carnitine ONLY if it has enough Vitamin C, B1, B6, iron, lysine, and methionine. Otherwise, a carnitine deficiency can occur. 

Serum (blood) testing for Carnitine levels is very important and can be ordered by your pediatrician. However, it is important to note that L-carnitine is not stored in the blood. It is stored in the muscle and tissue. Therefore, even if your child’s carnitine level is normal, it may still be low in the muscle and tissue. For this reason, supplementation decisions are often based on symptoms. 

Prescription L-Carnitine, also known as LevoCarnitine, is covered by insurance. 

Commonly seen in conjunction with carnitine deficiency:


Taurine is a sulfur-containing amino acid that supports both the immune and nervous systems. Therefore, it is needed most during illness and stress. 

Taurine helps protect the brain from glutamate toxicity by helping balance glutamate and GABA.

The body can make its own taurine from other amino acids but if you are eating a vegetarian or vegan diet, your levels of taurine will be lower

Additionally, taurine supplementation may interfere with seizure medication or antidepressants. 

These symptoms may warrant investigating a Taurine supplement:


In conclusion, there can be numerous reasons that your child diagnosed with autism has nutrient deficiencies. These deficiencies can result in a variety of symptoms that look a lot like autism, but the good news is that vitamin and mineral deficiencies are very treatable. 


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