Vitamin C

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vitCTreatment Overview

Vitamin C (ascorbic acid) is an essential water-soluble vitamin important for many normally occurring biological processes, including the production of neurotransmitters. Vitamin C also acts as an anti-oxidant, protecting the body against damaging free radicals.

Vitamin C can be purchased over-the-counter, online, or at grocery, drug, or health-food stores. It can be taken every day. Unfortunately, it is not clear what the proper dose for children with autism should be, but one research report used a dose of 8 grams/70 kg/day (or about 2 grams daily for a 40-pound child), divided into two or three doses. If you choose vitamin C as an alternative therapy, ask your child’s pediatrician what dose is appropriate for your child.

Some children with autism may have a vitamin C deficiency. One study demonstrated normal vitamin C levels among children with autism, while another reported low levels. Some investigators believe, however, that supplementation with vitamin C can be helpful even for children with normal levels of vitamin C.

Vitamin C has been shown to have a calming effect on behaviour in humans. In animals, stereotyped behaviour, one of the characteristics of autism, was reduced by treatment with vitamin C. Scientists hypothesize that vitamin C has these effects because it affects the brain’s response to an important neurotransmitter called dopamine 6.

Another explanation for the effectiveness of vitamin C is its anti-oxidant properties. Some researchers have theorized that children with autism may have more trouble managing free radicals than other children. Free radicals are damaging for the brain, immune system, and the body in general. Because it is an anti-oxidant, vitamin C can protect the body against the damaging effects of free radicals.

So far, only one controlled study has shown that vitamin C can help treat behavioural problems associated with autism. This double-blind experiment showed that high doses of vitamin C in children with autism had significant positive effects on behaviour, compared to their behaviour scores when they were taking a placebo. However, this study was very small (only 18 children) and has not been replicated.

Another research report showed that high doses of vitamin C may help sleep and gastrointestinal problems in children with autism. In this study, vitamin C was taken along with other vitamins, so it’s not clear which vitamin was responsible for the positive outcomes.

For most people, vitamin C is thought to be harmless. However, tolerance for vitamin C can vary. Therefore, you should watch your child carefully for signs of an upset stomach or diarrhea. Check with your child’s pediatrician before starting treatment.


  • Levy, S.E., and S.L. Hyman. 2005. “Novel treatments for autistic spectrum disorders.” Ment Retard.Dev Disabil.Res Rev. 11(2):131-142.
  • Dolske, M.C., et al. 1993. “A preliminary trial of ascorbic acid as supplemental therapy for autism.” Prog.Neuropsychopharmacol.Biol.Psychiatry 17(5):765-774.
  • Sankar, D. 1979. “Plasma levels of folates, riboflavin, vitamin B6, and ascorbate in severely disturbed children.” Journal of Autism and Developmental Disorders 9:73-82.
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  • Pierce, R.C., et al. 1991. “Chronic ascorbate potentiates the effects of chronic haloperidol on behavioral supersensitivity but not D2 dopamine receptor binding.” Neuroscience 45(2):373-378.
  • Deshpande, C., et al. 2006. “Antagonistic activity of ascorbic acid (vitamin C) on dopaminergic modulation: apomorphine-induced stereotypic behavior in mice.” Pharmacology 77(1):38-45.
  • Ming, X., et al. 2005. “Increased excretion of a lipid peroxidation biomarker in autism.” Prostaglandins Leukot.Essent.Fatty Acids 73(5):379-384.
  • Yao, Y., et al. 2006. “Altered vascular phenotype in autism: correlation with oxidative stress.” Arch.Neurol. 63(8):1161-1164.
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By Lara Pullen, PhD. The information from this page was reprinted with permission from Healing Thresholds. “Copyright (c) 2007, Healing Thresholds, Inc. All rights reserved”.


Autism Canada does not endorse treatments, interventions and therapies but lists them so people can make informed choice.  This site is for information purposes only and is a starting point for readers to look into options that may fit or resonate.  Remember, therapies for autism, like any condition, should be discussed with a trusted medical practitioner or certified therapist before use.

All information, data and material contained, presented or provided here is for general information purposes only and is not to be construed as reflecting the knowledge or opinions of Autism Canada, or as providing legal or medical advice. All treatment decisions should be made by the individual in consultation with a licensed health care provider.

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