Dietary Supplements and Autism


Bottle of a vitamin supplementDietary supplements (also called nutritional supplements) are intended to correct nutritional deficiencies.

Dietary supplements include vitamins, minerals, herbals and botanicals, amino acids, enzymes, and many other products. They come in a variety of forms including tablets, capsules, and powders, as well as drinks and energy bars.

There are numerous different types of supplements including amino acids, botanicals, cofactors, digestive enzymes, essential fatty acids, minerals, prebiotics probiotics and vitamins.

  • Vitamins include vitamin A, vitamin B-6, vitamin B-9, vitamin B-12, vitamin C, vitamin D and multi-vitamins.
  • Amino acids and derivatives include Carnitine, Dimethylglycine, Glutamate, Piracetam and Taurine.
  • Botanicals and derivatives include Ginkgo Biloba, Luteolin, Quercetin, St John's Wort and Yokukansan.
  • Enzymes and derivatives include. Bromelain, Dipeptidyl Peptidase, Papain, Tetrahydrobiopterin.
  • Essential fatty acids and derivatives include Cholesterol, Omega 3, Omega 6 and Omega 9.

Some people think that some autistic people have a range of nutritional and metabolic problems. These include low levels of nutrients, high levels of oxidative stress (a chemical state within cells that can increase cellular damage) and difficulties with metabolic processes (such as digestion). 

Some people think that these nutritional and metabolic differences may be the cause of some of the core features of autism (such as impaired communication and social difficulties) and related issues (such as challenging behaviours). They also think that some of these problems can be overcome by taking one or more dietary supplements, sometimes in combination with other therapies, such as special diets. 


Eating a healthy and varied diet is important for good health.

Food and drinks provide a range of nutrients and all vitamins and essential minerals are just that – essential for good health. If too little of any of these nutrients is consumed, nutrient deficiencies can occur, which cause ill health. Consuming too much of any of these nutrients can also cause poor health. It is unusual to consume too much via foods, however taking dietary supplements with high levels of nutrients does carry a risk of nutrient overload.

Some evidence shows that some autistic people may have nutritional and metabolic problems. However, the number of autistic people who have these problems is not clear. It is also not clear whether these problems or differences are any more common in autistic people than in other individuals. Possibly, these problems cause or worsen symptoms (of autism or related issues). Or maybe they arise because of autism, or they could be completely unrelated to autism. Nobody knows.

Most dietary supplements provide the same benefits for autistic people as they do to people who are not autistic. Some dietary supplements may make some problems worse for some autistic children and young people. 

Risks and safety 

Many dietary supplements contain active ingredients that can have strong effects in the body, so those pose risks. For example, according to the Office of Dietary Supplements: "... getting too much vitamin A can cause headaches and liver damage, reduce bone strength, and cause birth defects. Excess iron causes nausea and vomiting and may damage the liver and other organs."  Supplements are most likely to cause side effects or harm when people take them instead of prescribed medicines or when people take several supplements at the same time. Dietary supplements can also interact with certain prescription drugs in ways that can cause problems. For example, vitamin B6 can reduce the effectiveness of some epilepsy drugs, such as sodium valproate, carbamazepine and phenytoin.


Carnitine is the generic term for a group of natural substances that include L-carnitine, acetyl-L-carnitine, and propionyl-L-carnitine. 

Carnitine is found in nearly all cells of the body and in certain foodstuffs, such as meat, fish, poultry, and milk.

Carnitine plays a critical role in energy production. It transports long-chain fatty acids into the mitochondria (the ‘power stations’ inside the cell) so they can be metabolised to produce energy. It also transports the waste products out of the mitochondria to prevent their accumulation.

Carnitine supplements are sometimes used to treat anyone who is autistic who is believed to have one or more nutritional or metabolic deficiencies.

Some people think that carnitine can be used to treat a variety of issues in autistic people including ‘behaviour, cognition, socialisation, and health/physical traits associated with autism diagnosis’.

More information

Please see


Dimethylglycine (DMG) is a constituent of many important substances in the body, including amino acids, hormones and neurotransmitters.  It also appears to play an important role in the brain and in the immune system. 

Dimethylglycine is found naturally in plant and animal cells and certain foods are good sources, such as beans and liver.

DMG supplements are sometimes used to treat anyone who is autistic and who is believed to have one or more nutritional or metabolic deficiencies.

Some people think that DMG supplements can cause a range of behavioural improvements in autistic people including improved behaviour, better eye contact, and improved speech.

More information

Please see

Multi Vitamin and Mineral Supplements

Multivitamin/mineral supplements (MVMs) contain a combination of vitamins and minerals, and sometimes other ingredients as well.

Many types of multivitamin/ mineral supplements are on the market. Manufacturers choose which vitamins, minerals, and other ingredients, as well as their amounts, to include in their products.

Multivitamin/mineral supplements are sometimes used to treat anyone who is autistic and who is believed to have one or more nutritional deficiencies. 

Some people think that multivitamin/mineral supplements bring a range of benefits to autistic people, including a reduction in challenging behaviours and improved social communication.

More information

Please see

Omega 3 Fatty Acids 

Omega-3 fatty acids are essential fatty acids, that is, essential to good health.

Omega-3 fatty acids cannot be created within the human body and must therefore be obtained from foodstuffs, such as some
plant seeds and fish oil.

Omega-3 fatty acids are important for a number of bodily functions, including muscle activity, blood clotting, digestion, fertility, cell division and cell growth.

Some people think that some autistic peoeple have too little omega-3 and too much omega-6 in their bodies. They think that this imbalance can lead to a range of problems in autistic people.  

They think that taking omega-3 supplements can lead to a range of benefits including improvements to overall health, social interaction and communication

More information

Please see

Probiotics and Prebiotics

Probiotics are live microorganisms (such as bacteria) thought to be beneficial to human health.

Prebiotics are natural substances (non-digestible carbohydrates) found in some foods and are supposed to encourage the growth of probiotics.

Commonly used probiotics include Lactobacillus and Bifidobacterium, each of which includes specific types of bacteria.

Probiotics are commonly used to treat gastrointestinal problems such as diarrhoea, irritable bowel syndrome, and inflammatory bowel diseases (such as ulcerative colitis and Crohn’s disease)

Prebiotics and probiotics are sometimes given to autistic people with gastrointestinal problems.

Some people think that taking probiotics or prebiotics can restore normal gut functioning, which will in turn lead to behavioural improvements.

More Information

Please see

Vitamin B6

Vitamin B6 is naturally present in many foods (such as beans, nuts and cereals). It is also added to many other foods and is available as a dietary supplement.

Vitamin B6 performs a wide variety of functions in the body and is extremely versatile, with involvement in more than a hundred enzyme reactions, mostly concerned with metabolising proteins.

Vitamin B supplements are sometimes used to treat autistic people who are believed to have a vitamin B deficiency.

Some people think that taking vitamin B6 supplements can lead to behavioural improvements in autistic. For example, Nye and Brice reported that, if effective, ‘... B6-Mg
intervention would result in improved verbal skills, non-verbal skills, social interaction skills, and reactions to environmental stimuli and changes.’

More Information

Please see

Related Pages

Please see

Related Glossaries

27 May 2022