Which supplements have been shown to be helpful for autism, and which have not?

Answer:

As discussed below, no supplement can treat or cure autism spectrum disorder (ASD), but some supplements may help reduce symptoms such as irritability, tantrums, rule-breaking behavior, aggressive behavior, hyperactivity, and sleep disturbances. There are also supplements that, although touted, do not seem to be beneficial.

Possibly Useful

CoQ10 & Ubiquinol

Some research on autism has proposed oxidative stress as a potential cause of neuronal dysfunction and clinical symptoms in people with ASD. Ubiquinol, the active form of CoQ10 with strong antioxidant properties, has shown some benefit for communication and sleep, and decreased food rejection, based on parental reports when taken by children with ASD (Gvozdjakova, Oxid Med Cell Longev 2014). The authors noted that in the first days of supplementation, a small subset of children had increased anger, hyperactivity or sleep disturbance, which was managed by modifying the timing of the doses to morning and evening. More research is needed to confirm whether ubiquinol is beneficial for symptoms of ASD.

For more about ubiquinol, including our most recent product tests and reviews, see the CoQ10 & Ubiquinol Supplements Review.

Digestive Enzymes

Clinical studies have assessed if supplementation with digestive enzymes that help break down protein (i.e., protease enzymes such as pepsin and papain) improve symptoms among children with autism, but results are conflicting (Saad, Clin Psychopharmacol Neurosci 2015; Munasinghe, J Autism Dev Disord 2010). An investigational drug called CM-AT (by Curemark), which is a high-protease pancreatic enzyme composed mainly of chymotrypsin (which helps release tryptophan from protein), has been shown to improve irritability/agitation, hyperactivity, and inappropriate speech among children with autism (Pearson, JAMA Netw Open 2023), but this drug has not yet been approved by the FDA.

Fish Oil

Several very small, preliminary studies have linked supplementation with omega-3 fatty acids with decreased hyperactivity in children with ASD or improvement in other ASD symptoms. The studies used daily doses of 1,000 mg to 1,500 mg of omega-3 fatty acids (in the case of the 1,500 mg dose, 840 mg was from EPA and 700 mg from DHA) (Meiri, J Child Adolesc Psychopharmacol 2009; Bent, J Autism Dev Disord 2011; Amminger, Biol Psychiatry 2007).

For more about omega-3s and fish oil, including our most recent product tests and reviews, see the Fish/Marine Oil Supplements Review.

Folic acid (Vitamin B-9)

Observational studies in Israel and Norway (countries without required folate fortification of food) have linked taking a folic acid supplement or a multivitamin containing folic acid during pregnancy with a lower chance of having a child with ASD compared to not taking folic acid (Levine, JAMA Psychiatry 2018; Suren, JAMA 2013; Roth JAMA 2011). Be aware that excessively high blood levels of folate (>59 nmol/L) in pregnant women has been associated with an approximate twofold increased chance of ASD compared to lower levels (Raghavan, International Meeting for Autism Research 2016).

A small study in China showed that folic acid supplementation may improve some, but not all, behaviors among children with ASD compared to no supplementation (Sun, Nutrients 2016). However, fortification of food with folic acid is not required in China, and it is unclear if folic acid supplementation would be beneficial for children with ASD in countries that require fortification, such as the U.S.

For more about folic acid, including our most recent product tests and reviews, see the B Vitamin Supplements Review.

A form of folic acid sold as the medication leucovorin calcium (Wellcovorin) (also called folinic acid) has been touted for treating autism, although supporting evidence appears to be very limited. The American Academy of Pediatrics does not recommend its routine use for autistic children, as questions remain about who may benefit, what doses are appropriate, and if long-term use is safe (AAP, 2025).

Interest in leucovorin for autism is largely due to its ability improve folate levels and verbal communication in people with cerebral folate deficiency (CFD), an autoimmune condition that causes autistic features and is present in about 38% of people with autism (FDA, 9/22/2025; Rossignol, J Pers Med 2021; Ramaekers, N Engl J Med 2005). On September 22, 2025, the U.S. FDA initiated the process to approve leucovorin calcium tablets for people with CFD (FDA, 9/22/2025). A 12-week study in the U.S. among 48 children with ASD and language impairment showed that taking 2 mg/kg/day (maximum daily dose 50 mg/day) of leucovorin calcium in two divided doses daily for 12 weeks improved verbal communication by 5 points or more (on scales ranging from 50 to 150 or 45 to 155) in 65% of participants compared to only 24% in the placebo group. The difference compared to placebo was slightly greater among those who were positive for anti-folate receptor autoantibody, but there was no significant difference among those who were antibody negative (Frye, Mol Psychiatry 2018). Another study conducted in India among 40 children with autism found that taking the same dose of leucovorin calcium for 24 weeks slightly reduced autism symptom severity by 1.2 points (on a scale of 15 to 60) compared to placebo, and the benefit was greater among those with high levels of anti-folate receptor autoantibodies compared to those with low levels (Panda, Eur J Pediatr 2024). However, this study was later retracted due to errors in how the findings were presented and an inability to replicate the original findings from the dataset provided by the authors (Panda, Eur J Pediatr 2026).

L-Carnitine

One preliminary clinical trial found that L-carnitine, taken daily (50 mg per kg bodyweight) as a liquid supplement, significantly improved disease severity (based on clinician assessment), as well as cognition (based on parent assessment), but not speech, sociability or behavior based on parent assessment in children with ASD (Geier, Med Sci Monit 2011).

Melatonin

An estimated 50% to 80% of children with ASD may suffer from sleep difficulties or insomnia (Malow, J Autism Dev Disord 2013), and several studies have found that individuals with ASD to have lower levels of melatonin or melatonin metabolites than those without ASD (Rossignol, Dev Med Child Neurol 2011). Consequently, there is interest in melatonin supplementation for improving symptoms of this condition. An analysis of 18 studies of people with ASD (mostly children and adolescents) found that melatonin supplementation (in doses ranging from 0.75 mg to 25 mg daily) significantly improved the time it took to fall asleep (sleep latency) and sleep duration, and, in some individuals, also improved daytime behavior (Rossignol, Dev Med Child Neurol 2011). Other studies also found that a daily dose of 1 mg, 3 mg, or 4 mg of melatonin improved sleep latency in children with ASD (Hayashi, J Autism Dev Disord 2021; Malow, J Autism Dev Disord 2013). Taking melatonin may improve sleep efficiency, sleep latency, and sleep duration among people with ASD similarly to exercising five times weekly, although a combination of melatonin and exercise does not appear to have synergistic effects (Tse, J Autism Dev Disord 2023).

For more about melatonin, including our most recent product tests and reviews, see the Melatonin Supplements Review.

Multivitamin and Multimineral Supplements

Multivitamin and multimineral supplements are among the most widely recommended supplements by physicians for children with ASD. One randomized, double-blind, placebo-controlled study involving 141 children and adults with ASD found supplementation with a specially formulated liquid multivitamin/mineral (see ingredients and amounts here) that also contained CoQ10, MSM and N-acetyl cysteine (NAC), improved the nutritional and metabolic status of children with this condition, and significantly reduced symptoms such as hyperactivity and tantrums (Adams, BMC Pediatrics 2011). The supplement was given in three equal doses at breakfast, lunch and dinner.

For more about multivitamins, including our most recent product tests and reviews, see the Multivitamin Supplements Review.

N-Acetyl Cysteine (NAC)

The amino acid N-acetyl cysteine (NAC) has been found to reduce irritability, but not other symptoms, in children with ASD (Hardan, Biol Psychiatry 2012) and in children taking risperidone (an atypical antipsychotic drug sometimes prescribed for people with ASD) (Ghanizadeh, BMC Psychiatry 2013). The dose in these studies ranged from 900 mg to 2,700 mg daily, which was generally well tolerated.

For more about NAC and our tests of products, see the N-Acetyl Cysteine Supplements Review.

Probiotics

The gut microbiota in people with ASD has been found to differ from that of people without autism (Kong, Nutrients 2019), and this has been associated with increased irritability, tantrums, aggressive behavior and sleep disturbances. Children with ASD can also experience significantly more gastrointestinal symptoms, including diarrhea, constipation and abdominal pain, than others, and probiotics may be helpful for some of these symptoms (Critchfield, Gastroenterol Res Pract 2011).

Probiotics may also improve some of the core symptoms of ASD. Two small studies in children and young adults with ASD found that supplementing with a specific strain of Lactobacillus improved some symptoms such as rule-breaking behavior and hyperactivity/impulsivity, as well as global functioning compared to placebo (Kong, Nutrients 2019; Liu, Nutrients 2019). However, larger and longer-term studies are needed to confirm these results.

For more details about these studies and the probiotics used, see the Probiotic Supplements Review.

Vitamin C

One small study found significant improvements in sensory motor behaviors (such as pacing, flapping, rocking and whirling) in children with ASD who received a high dose of vitamin C (8,000 mg per 70 kg of body weight) daily when compared to placebo. However, there were no significant improvements in social or affective behavior, or language (Dolske, Prog Neuropsychopharmacol Biol Psychiatry 1993). It is important to note, however, that taking such a large dose of vitamin C may cause diarrhea in some people.

For more about Vitamin C, including our most recent product tests and reviews, see the Vitamin C Supplements Review.

Vitamin D

Low blood levels of vitamin D have been associated with increased chance of ASD (Wu, J Bone Mineral Res 2017). One small clinical study suggests that vitamin D given to children with ASD and vitamin D deficiency may modestly improve ASD severity based on two scale, although it does not seem to improve aberrant behaviors such as irritability, hyperactivity, social withdrawal, and inappropriate speech (Javadfar, Nutrition 2020). There is no evidence that vitamin D improves symptoms of ASD in children who already have adequate levels of vitamin D.

For more details, and our tests of products, see the Vitamin D Supplements Review.

Probably Not Useful

L-Carnosine

L-Carnosine has been evaluated for a variety of brain-related conditions based on its neuroprotective effects, but it doesn’t not appear to be beneficial for ASD. Although a small clinical study showed that taking an 800 mg daily dose of L-carnosine for 8 weeks significantly improved scores on the Gilliam Autism Rating Scale (a measure of ASD severity) in children with ASD (Chez, J Child Neurol 2002), subsequent analysis of data from this study and three other studies evaluating L-carnosine for ASD found that, overall, taking L-carnosine did not significantly improve socialization, communication or behavior compared to placebo (Abraham, Amino Acids 2021).

Sulforaphane and Broccoli Extract

Sulforaphane, an isothiocyanate compound found in the seeds and sprouts of cruciferous vegetables such as broccoli, has demonstrated antioxidant, anti-inflammatory, neuroprotective, and improved mitochondrial function effects in laboratory studies. Because ASD has been linked with oxidative stress, inflammation, and mitochondrial dysfunction, there has been interest in sulforaphane for treating this condition. Despite promising initial clinical results, more recent clinical research suggests limited benefit, if any, of sulforaphane for ASD.

An early study among young men (ages 13 to 27) with ASD found that taking sulforaphane derived from broccoli sprout extract (about 9 to 27 mg per day depending on body weight) for 18 weeks improved aberrant behavior and social responsiveness, respectively, by 34% and 17% compared to baseline, while those in the placebo group showed improvements of less than 3%. These between-group differences were statistically significant (Singh, Proc Natl Acad Sci U S A 2014). However, a subsequent study among children (ages 3 to 12) with ASD showed that taking sulforaphane (as Avmacol tablets by Nutramax Laboratories) for 15 weeks did not significantly improve aberrant behavior, verbal communication, repetitive behavior, or social interaction compared to placebo (Zimmerman, Mol Autism 2021), and a 12-week study showed that this product improved only clinician-rated but not parent-caregiver-rated scores of autism behaviors when given to children (ages 5 to 15) with ASD (Smith, ACNP 59th Annual Meeting 2020). Furthermore, a 36-week study among children (ages 3 to 7) with ASD found no behavioral benefit of sulforaphane supplementation (50 mcmol or about 9 mg per day) compared to placebo (Magner, Nutrients 2023). In addition, an analysis of data from 6 clinical studies that involved 333 children and teens with ASD showed that taking sulforaphane did not significantly improvement behaviors such as irritability, hyperactivity and stereotypy compared to placebo. Sulforaphane slightly improved mannerisms and social awareness/communication when assessed after 8 to 10 weeks but not after 18 to 36 weeks (Long, BMC Pharmacol Toxicol 2025).

Vitamin B-12

ASD has been linked with lower blood levels of vitamin B-12 in some, but not all studies, possibly due to a nutrient deficient diet or malabsorption syndrome among people with autism (Zwierz, Nutrients 2025). Consequently, there is interest in vitamin B-12 for improving symptoms of this condition. However, clinical studies involving methylcobalamin injections have shown mixed results, and there do not appear to be any placebo-controlled studies evaluating the effects of vitamin B-12 when taken by mouth for ASD.

A 6-week study conducted at the UC Davis M.I.N.D. Institute among 30 children with ASD showed no significant improvements in behavior tests among those given subcutaneous injections of methylcobalamin compared to those given placebo (saline) (Bertoglio, J Altern Complement Med 2010). On the other hand, a study among 50 children with ASD showed that receiving methylcobalamin injections for 8 weeks improved clinician-rated symptoms compared to placebo and symptom improvement was linked with improvement in cellular methylation capacity (i.e., the body’s ability to perform methylation reactions required for protein function and DNA repair) (Hendren, J Child Adolesc Psychopharmacol 2016).