Carnitine
What is Carnitine?
Carnitine is an amino acid produced by the body, found in certain foods, and nutrition supplements. One form of carnitine, L-carnitine, is the most common. There are a few other types of L-carnitine (ex: Acetyl L-carnitine)
Carnitine is important for optimal brain function and energy production in the body and may protect against some chronic diseases. It is also very important for mitochondrial function (it both transports long-chain fatty acids in, and transports toxic compounds out).
Acetyl-L-carnitine is often used in research studies because it is better absorbed from the small intestine than L-carnitine and can cross the blood-brain barrier and get into brain tissue more efficiently. [1]
Some people with autism (~10-20%) seem to have L-carnitine metabolism disorders and for these patients, a diet high in carnitine and dietary supplementation with L-carnitine is beneficial. [2]
Carnitine is suspected to have a link to in autism based on these 3 lines of evidence: [3]
There is increased altered mitochondrial function in those with ASD
The relationships between l-carnitine/acylcarnitine levels and the symptoms of autism (see research section below)
The genetic aspects of autism associated with l-carnitine metabolism
Food Sources of Carnitine
Fish
Dairy products (cheese, milk)
Asparagus
Recommended Intake
Carnitine is the product of two amino acids called lysine and methionine. Since the liver and kidneys produce sufficient amounts of lysine and methionine to create carnitine and meet daily needs, healthy children and adults do not need to consume additional carnitine from food or supplements. For this reason, a recommended daily amount has not been established.
Deficiency
Carnitine deficiency can be primary or secondary. A primary deficiency means that there is a genetic disorder that would cause the body to not produce sufficient levels of carnitine. This typically manifests itself by five years of age. Symptoms include skeletal muscle weakness, hypoglycemia, and cardiomyopathy. [4]
A secondary deficiency is caused by other health conditions or disorders, such as chronic renal failure, or reduced carnitine absorption in the gut (may be caused by certain antibiotics).
Toxicity
Taking excessive amounts of carnitine can cause carnitine toxicity, which can include nausea, vomiting, diarrhea, abdominal cramps, and even a fishy body odor. In adults, this amount was 3 grams/day, but we do not have a known upper limit for children, though it’s logical to say that it would be a fraction of the amount for adults. One study suggests that these symptoms are observed with a dose of 200 mg/kg/day. [3]
Supplements
Carnitine can be taken in supplemental form when needed and can be found as L-carnitine, acetyl-L-carnitine, and propionyl-L-carnitine. Per one study, doses of about 50–100 mg/kg/day are generally well tolerated. [3] Supplementation should be used with the guidance of a healthcare provider.
Examples
Liquid
Capsules
Note: All supplements are linked to Amazon for convenience, however, buying supplements on Amazon does not guarantee quality, as there are many “unverified resellers” selling nutrition supplements. To buy supplements that are verified to be sent directly to the consumer, you can create an account on the Autism Dietitian FullScript and search for the respective supplement under “Catalog”.
DISCLAIMER: Before starting any supplement or medication, always consult with your healthcare provider to ensure it is a good fit for your child. Dosage can vary based on age, weight, gender, and current diet.
Carnitine & Autism in the Research
Carnitine & Autism
Studies on the Effects of Carnitine Treatment on Patients With ASD Without Any Known Genetic Causes
L-carnitine therapy (50 mg/kilogram-bodyweight/day) administered for 3-months significantly improved several clinical measurements of ASD severity as measured by CARS, but subsequent studies are recommended. [5]
L-carnitine therapy (100 mg/kg -bodyweight/day) administered for 6 months significantly improved the autism severity as measured by CARS, but subsequent studies are recommended. [6]
Supplementation with L-carnitine showed improvements on the Clinical Global Impression Scale (CGIS) and other clinical variables. [7]
Some reported side effects including heavy odor, diarrhea, and sporadic vomiting.
Studies on the Effects of Carnitine Treatment on Patients With ASD With Associated Genetic Syndromes
Children with mitochondrial diseases and hyperlacticacidemia who supplemented with carnitine, a B complex, CoQ10, and folic acid saw improvements. [8]
Those with intellectual disability alone had more benefits than ASD, and saw an improvement in hypotonia (low muscle tone)
A child with primary carnitine deficiency presented with atypical features of the disease, including a developmental delay involving language skills, concentration, and attention span, as well as autistic features and brain alterations apparent in magnetic resonance imaging. [9]
They saw an improvement in muscle weakness, language skills, and IQ improved by 15 percentage points. The patient remained inattentive and displayed a slight improvement in ASD features.
A study with children with 4q-syndrome and ASD or developmental delay were prescribed carnitine, CoQ10, omega-3s, and multivitamins and saw improvements. [10]
The perceived benefits of these supplements were a stronger immune system, increased energy levels and muscle strength, and improved speech and language development. No clinical evaluation performed.
Carnitine & Mitochondrial Dysfunction in ASD
Some studies suggest that children with ASD and mitochondrial disease may have certain characteristics such as fatigability, gastrointestinal disorders, unusual types of neurodevelopmental regression, seizures/epilepsy, and motor delay. [11]
Several treatments that target mitochondria appear to have evidence for use in children with ASD, including cofactors such as L-Carnitine and the ketogenic diet.
Visit the Mitochondrial Dysfunction note for more information
Carnitine & Neuroprotection
Treatment with L-carnitine can ameliorate metabolic imbalances in many inborn errors of metabolism and may also be a treatment to improve outcomes after neonatal and pediatric brain injury. [12]
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[1] Liu J, Head E, Kuratsune H, Cotman CW, Ames BN. Comparison of the effects of L-carnitine and acetyl-L-carnitine on carnitine levels, ambulatory activity, and oxidative stress biomarkers in the brain of old rats. Ann N Y Acad Sci. 2004 Nov;1033:117-31. doi: 10.1196/annals.1320.011. PMID: 15591009.
[2] Demarquoy C, Demarquoy J. Autism and carnitine: A possible link. World J Biol Chem. 2019 Jan 7;10(1):7-16. doi: 10.4331/wjbc.v10.i1.7. PMID: 30622681; PMCID: PMC6314880.
[3] Malaguarnera M, Cauli O. Effects of l-Carnitine in Patients with Autism Spectrum Disorders: Review of Clinical Studies. Molecules. 2019 Nov 22;24(23):4262. doi: 10.3390/molecules24234262. PMID: 31766743; PMCID: PMC6930613.
[4] Almannai M, Alfadhel M, El-Hattab AW. Carnitine Inborn Errors of Metabolism. Molecules. 2019 Sep 6;24(18):3251. doi: 10.3390/molecules24183251. PMID: 31500110; PMCID: PMC6766900.
[5] Geier DA, Kern JK, Davis G, King PG, Adams JB, Young JL, Geier MR. A prospective double-blind, randomized clinical trial of levocarnitine to treat autism spectrum disorders. Med Sci Monit. 2011 Jun;17(6):PI15-23. doi: 10.12659/msm.881792. PMID: 21629200; PMCID: PMC3539542.
[6] Fahmy S.F., El-Hamamsy M., Zaki O., Badary O.A. Effect of l-carnitine on behavioral disorder in autistic children. Value Heal. 2013;16:A15. doi: 10.1016/j.jval.2013.03.092
[7] Goin-Kochel R.P., Scaglia F., Schaaf C.P., Berry L.N., Dang D., Nowel K.P., Laakman A.L., Dowell L.R., Minard C.G., Loh A., et al. Side Effects and Behavioral Outcomes Following High-Dose Carnitine Supplementation Among Young Males With Autism Spectrum Disorder: A Pilot Study. Glob. Pediatr. Heal. 2019;6 doi: 10.1177/2333794X19830696.
[8] Guevara-Campos J, González-Guevara L, Cauli O. Autism and intellectual disability associated with mitochondrial disease and hyperlactacidemia. Int J Mol Sci. 2015 Feb 11;16(2):3870-84. doi: 10.3390/ijms16023870. PMID: 25679448; PMCID: PMC4346931.
[9] Guevara-Campos J, González-Guevara L, Guevara-González J, Cauli O. First Case Report of Primary Carnitine Deficiency Manifested as Intellectual Disability and Autism Spectrum Disorder. Brain Sci. 2019 Jun 13;9(6):137. doi: 10.3390/brainsci9060137. PMID: 31200524; PMCID: PMC6628273.
[10] Strehle EM. Dysmorphological and pharmacological studies in 4q- syndrome. Genet Couns. 2011;22(2):173-85. PMID: 21848010.
[11] Frye RE. Mitochondrial Dysfunction in Autism Spectrum Disorder: Unique Abnormalities and Targeted Treatments. Semin Pediatr Neurol. 2020 Oct;35:100829. doi: 10.1016/j.spen.2020.100829. Epub 2020 Jun 23. PMID: 32892956.
[12] Ferreira GC, McKenna MC. L-Carnitine and Acetyl-L-carnitine Roles and Neuroprotection in Developing Brain. Neurochem Res. 2017 Jun;42(6):1661-1675. doi: 10.1007/s11064-017-2288-7. Epub 2017 May 16. PMID: 28508995; PMCID: PMC5621476.
Authors
Brittyn Coleman, MS, RDN/LD, CLT
