Autism Spectrum Disorder (ASD), or what is now also known as Autism Spectrum Condition (ASC), is a neurological or neurodevelopmental condition characterized by difficulties in social, motor, cognitive, and language development.

Children with ASD are characterized by a disorder in neuronal connectivity, abnormal synaptic function, and neurotransmitter imbalances.

It is called a "Spectrum" because it manifests differently in each person.

Due to the neurobiological and behavioral alterations present in ASD/ASC, nutritional needs can be compromised, which makes the analysis of the role of supplementation in people with this condition especially relevant.

It has been discovered that children with ASD/ASC often have increased or reduced sensory sensitivity, which influences their eating habits. This can manifest as a rejection of or preference for certain textures, smells, tastes, specific temperatures, the appearance of the food, etc. These characteristics can lead to a very selective and unvaried diet, hindering proper nutrition.

Therefore, children and adults with ASD/ASC can be particularly susceptible to nutritional inadequacies and deficiencies as a result of often self-limited diets, and as a consequence of this unbalanced diet, behavior, sleep, concentration, etc., may be affected.

Children with ASD/ASC often have a deficiency of vitamin D, magnesium, B-complex vitamins, and omega-3 fatty acids. These deficiencies could be the result of food selectivity or impaired gastrointestinal absorption.

Furthermore, it is important to emphasize that an unvaried diet can not only generate nutrient deficiencies but also negatively affect intestinal health. In people with ASD/ASC, high food selectivity often leads to a predominant consumption of ultra-processed foods, sugars, and refined flours. This limited diet impoverishes the diversity of the gut microbiota, which can hinder both the production of key neurotransmitters and the proper absorption of nutritional supplements. For this reason, a dietary base that favors the development of a healthy microbiota is fundamental for supplementation to be truly effective.

It is for this reason that nutrition and supplementation are so important for people with this condition.

Scientific evidence has identified various nutrients and compounds that could play a relevant role in the neurological development, behavioral regulation, and general well-being of people with ASD/ASC. Below are those that have been most studied in the current literature.

The central nervous system contains polyunsaturated fatty acids (PUFAs), especially docosahexaenoic acid (DHA), which cannot be synthesized by the human body but must be provided through nutrition. Some studies reported that imbalances or deficiencies in fatty acids may be involved in childhood neurological disorders, including attention deficit hyperactivity disorder (ADHD), dyslexia, and the autism spectrum disorders.

Foods rich in omega-3 fatty acids: Fatty fish and seafood (sardines, salmon, anchovies, trout, tuna), flax and chia seeds (ground), walnuts.

A clinical trial with 54 children showed that the administration of omega-3 fatty acids (EPA+DHA) for 8 weeks improved stereotypical behaviors, social communication, and overall ASD scores.

Another study also reported that omega-3 supplementation for 12 weeks decreased hyperactivity in children with ASD.

Vitamin D plays a role in the regulation of synaptic plasticity and the dopaminergic system. In addition, it helps reduce oxidative burden. Children with ASD/ASC have lower serum vitamin D levels, which may be one of the environmental factors contributing to the development of autism in genetically susceptible children.

Studies have found that children with autism often have low levels of vitamin D. It is believed that this deficiency could influence brain development or some symptoms of autism, although it is not known for certain whether it is a cause or a consequence.

The body is capable of producing vitamin D naturally when the skin is directly exposed to sunlight. However, few foods contain vitamin D in significant amounts. Among the main dietary sources are cod liver oil, fatty fish (such as salmon or tuna), egg yolk, fortified cereals, and plant-based drinks enriched with this vitamin.

It is important to adjust the dose according to each case and monitor levels.

Probiotics are live microorganisms that, when administered in adequate amounts, promote intestinal health, while prebiotics are non-digestible fibers (Fructooligosaccharides (FOS), Galactooligosaccharides (GOS)) that feed the beneficial bacteria in the intestine.

In people on the autism spectrum, alterations in the gut microbiota have been observed that could be related to gastrointestinal symptoms (such as abdominal pain, constipation, or diarrhea) and also related to changes in behavior, irritability, and anxiety.

This is explained by the gut-brain axis, a bidirectional communication pathway in which the microbiota influences the nervous system through the production of neurotransmitters such as serotonin, GABA, and glutamate, which regulate behavior, sleep, and mood.

It is important to consider certain practical aspects when using probiotics in people with ASD/ASC. Since each probiotic strain may have different effects or approaches, it is essential to select those with scientific backing. Additionally, it is recommended to seek professional advice to determine the appropriate type and dosage.

Magnesium is an essential mineral for neurological function and participates in more than 300 enzymatic reactions, including synaptic transmission and the modulation of neurotransmitters such as glutamate, GABA, and serotonin, all linked to behavior and cognition.

Although there are not yet high-level clinical trials, various experimental and observational studies have shown improvements in ASD and ADHD symptoms with magnesium supplementation.

- In 18 studies, approximately 50% of children with ASD showed improvements without adverse effects. Parents reported better attention, learning, language, and eye contact.

- A study on 33 children with ASD who took magnesium (6 mg/kg/day for 6 months) found:

• Low intracellular magnesium levels before treatment.
• Significant improvements in social interactions, communication, and repetitive behaviors in 23 children.
• Reappearance of symptoms upon discontinuing supplementation.

Among the different forms of magnesium, magnesium threonate is notable for its ability to cross the blood-brain barrier, making it especially effective for improving cognitive and behavioral functions.

Magnesium's relationship with key neurotransmitters

• Serotonin: Associated with mood, learning, and sleep. Its production depends on magnesium; low magnesium levels = less serotonin = mood and behavioral alterations.
• Melatonin: Regulates sleep and is produced from serotonin. Therefore, magnesium indirectly contributes to better rest at night.
• GABA: An inhibitory neurotransmitter related to calm and relaxation. Magnesium helps restore its balance, which can reduce symptoms such as anxiety, repetitive behaviors, and cognitive difficulties.

Vitamin B6 is important for the synthesis of numerous neurotransmitters, such as GABA, serotonin, dopamine, and norepinephrine, among others, which indicates that supplementation with vitamin B6 can enhance many neurotransmitter systems. This could reduce behavioral problems, improve general behavior, attention, and anxiety, and potentially regulate mood, sleep, and emotional response.

Vitamin B9, also known as folic acid, is key in processes such as DNA methylation and the production of neurotransmitters—functions that are altered in ASD/ASC. Abnormalities in its metabolism are associated with oxidative stress and the risk of ASD/ASC. Its supplementation prenatally, especially before and during the first trimester, can reduce this risk.

The active form of folate, methylfolate, can cross the blood-brain barrier more easily and does not depend on enzymes such as MTHFR, which makes it an effective option, especially in people with genetic variations in this pathway.

An open-label study with 66 autistic children who underwent vitamin B9 supplementation for 3 months showed improvements in sociability, language, emotional expression, and communication, along with a normalization of metabolic markers such as homocysteine and glutathione.

Methylcobalamin, an active form of vitamin B12, has been studied as a potential treatment for ASD. It can improve methylation; therefore, greater methylation and glutathione production can enhance the body's ability to detoxify harmful substances, which could reduce toxic load and impact neurological health. Studies show improvements in behavior, communication, and cognitive functions.

It should be noted and emphasized that supplementation with the vitamins and minerals mentioned above must be personalized and supervised by a healthcare professional. Although the preliminary results of the studies mentioned above regarding some nutrients are promising, more quality research is still required to determine optimal dosages, effective combinations, and potential long-term effects.

Nutritional supplementation for people with Autism Spectrum Disorder/Condition (ASD/ASC) emerges as a valuable complementary tool in the comprehensive approach to this condition. Given that many people on the spectrum have dietary difficulties and a higher predisposition to nutritional deficiencies, the controlled and personalized incorporation of certain nutrients can contribute positively to their physical, emotional, and cognitive well-being.

Nutrients such as omega-3 fatty acids, vitamin D, magnesium, probiotics, as well as B-complex vitamins, have shown potential benefits in various studies regarding key aspects such as behavior, sleep, communication, attention, and emotional regulation. These effects can be explained in part by their influence on the nervous system, neurotransmitter production, and gut health.

However, it is fundamental to remember that supplementation does not replace other therapeutic interventions nor should it be applied in a generalized way. Each person with ASD/ASC is unique, and therefore supplementation must be individualized, evaluated, and supervised by healthcare professionals who consider specific needs, the clinical context, and potential interactions or contraindications.

Considering the above, well-applied supplementation can be an ally in improving the quality of life for people on the autism spectrum, provided it is based on scientific evidence, professional evaluation, and a holistic view of health.