Breaking Through the Mental Fog

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Does your brain ever feel like it’s mired in a thick fog? Have difficulty concentrating? Poor memory? These symptoms may point to an L-Carnitine deficiency. 

L-Carnitine is a vital amino acid which promotes healthy neural levels of acetylcholine, an important neurotransmitter that aids memory and proper brain function. Research suggests that an L-Carnitine deficiency may be implicated in a number of conditions, including Fibromyalgia, ME/CFS (‘chronic fatigue syndrome’), Lyme disease, diabetes, Alzheimer’s, dementia, and autism.

The Role of L-Carnitine

L-Carnitine is produced in the liver and kidneys from two essential amino acids, lysine and methionine. It can be found in nearly every cell in the body and is necessary for the proper metabolism of fat.

In addition to helping sharpen mental focus and concentration, L-Carnitine plays a key role in energy production. It transports long-chain fatty acids across the mitochondrial membrane so that they can be burned to produce energy.

Who Needs L-Carnitine?

The average healthy individual does not need to supplement L-Carnitine because the body makes most of what is needed and the rest is provided by a well-balanced diet. The highest concentrations of L-Carnitine are found in red meats. Generally speaking, the redder the meat, the more L-Carnitine it contains. Smaller amounts can be found in poultry and dairy products. However:

• Because vegans do not eat any animal-derived foods, they may need to supplement L-Carnitine.

• Some people’s bodies, for genetic or medical reasons, are not able to produce adequate amounts of L-Carnitine and they may need to take an L-Carnitine supplement.

• People with certain conditions, like ME/CFS, mitochondrial disorders and diabetes, are frequently found to be deficient in L-Carnitine.

• L-Carnitine levels are also known to decrease with age and may contribute to the cognitive difficulties found in Alzheimer’s and dementia patients.

Which Form of L-Carnitine is Best?

L-Carnitine comes in several different forms, but the acetylated form – known as Acetyl-L-Carnitine – is best for supporting healthy mental and cognitive function while also promoting the generation of energy.

Acetyl-L-Carnitine crosses the blood-brain barrier more readily than other forms of L-Carnitine. The fact that the acetylation of L-Carnitine is a normal event in the human brain may explain why greater activity is found in the brain when using Acetyl-L-Carnitine rather than other forms.

L-Carnitine’s Connection to ME/CFS

Several studies have looked at whether an L-Carnitine deficiency could contribute to ME/CFS symptoms, and at its use as a possible therapeutic option.

A 1998 study measured L-Carnitine levels in subjects from Japan and Sweden who had a number of different diseases. They found that ME/CFS patients from both countries were deficient in L-Carnitine, leading them to conclude that an L-Carnitine deficiency might be a characteristic abnormality in ME/CFS.(1)

In a 1997 study, 30 ME/CFS patients were included in a crossover trial comparing supplemental L-Carnitine and amantadine, a medication used to treat fatigue in multiple sclerosis patients. Each therapy was given for two months, with a two-week washout period between. In the L-Carnitine phase, patients took one gram (1,000 mg) of L-Carnitine three times a day.

In the amantadine phase, half of the patients had to quit taking the medication due to side effects. Those who completed the amantadine phase showed no improvement in their symptoms. However, in the L-Carnitine phase, the patients showed significant improvement, with all but one completing the phase. The greatest improvement took place between four and eight weeks of L-Carnitine supplementation.(2)

The most recent study, published in July 2011, analyzed blood samples of 44 ME/CFS patients and 49 healthy controls for L-Carnitine and concentrations of 35 individual essential acylcarnitine compounds in plasma. They found that the patients with ME/CFS exhibited significantly altered levels in eight of the concentrations, with some of the concentrations averaging 30% to 40% lower than controls. In conclusion, the researchers hypothesized that “the administration of omega-3 fatty acids in combination with L-Carnitine would increase carnitine palmitoyltransferase-I activity and improve chronic fatigue syndrome symptomology.”(3)

Overall, as medical nutrition pioneer Dr. Melvyn Werbach, MD, states in his classic Nutritional Strategies for Treating Chronic Fatigue Syndrome, “In CFS, serum carnitine levels appear to be a biochemical marker for both symptom severity and ability to function.”(4)

L-Carnitine and the Physical & Mental Fatigue of Aging

According to a 2007 study, L-Carnitine supplementation improved both energy levels and cognitive function in centenarians (people 100 years of age and older). A total of 66 individuals between the ages of 100 and 106 who reported fatigue after even slight physical activity were randomized to receive either 2 grams (2,000 mg) of L-Carnitine per day or a placebo for six months.

Compared with the placebo group, the group who took the L-Carnitine demonstrated a significant:

• Reduction of fat mass.

• Gain in total muscle mass.

• Reduction in physical and mental fatigue.

• Reduction of fatigue severity.

• Improvement in cognitive function scores.

• Improvement in walking capacity.(5)br />

L-Carnitine and Autism Research

The first randomized controlled clinical trial studying the use of L-Carnitine as a potential therapy for autism was published in June 2011. Thirty children with Autism Spectrum Disorder (ASD) were divided into two groups. One group received 50 mg of L-Carnitine per kilogram of body weight (e.g., a 60-pound child would get 1,364 mg of L-Carnitine a day) and the other group received a placebo.

After three months, the children taking L-Carnitine showed “significant improvements” in the severity of ASD. Some of the areas in which the children improved included their ability to relate to people, body use, adaptation to change, listening response, verbal communication, sociability, sensory/cognitive awareness, and health/physical behavior.(6)

L-Carnitine and Diabetes

Insulin resistance, which plays an important role in the development of type 2 diabetes, may be associated with a defect in fatty-acid oxidation in muscles. Early research suggests that supplementation with L-Carnitine intravenously may improve insulin sensitivity in diabetics by decreasing fat levels in muscle and may lower glucose levels in the blood by supporting its more rapid oxidation in cells.(7)

Diabetic neuropathy is a painful condition that often occurs in diabetics when high blood sugar levels damage nerves in the body – usually in the extremities. In a 2006 study, 333 individuals with diabetic neuropathy were given Acetyl-L-Carnitine or a placebo for one year. The Acetyl-L-Carnitine was administered by IM injection at a dose of 1,000 mg for the first 10 days, followed by an oral dose of 2,000 mg daily for the remaining 355 days.

After 12 months, nerve conduction, amplitude and pain scores were all significantly better. Pain scores were reduced by 39% in the Acetyl-L-Carnitine group but only by 8% in the placebo group. The researchers concluded that Acetyl L-Carnitine is “a promising treatment option in patients with diabetic neuropathy.”(8)

Need-to-Know Information

Dosage:  The suggested dosage will vary depending on the purpose for supplementing with Acetyl-L-Carnitine. There is no official RDA for L-Carnitine, but a typical dose is 500 mg per day. Where special needs are a possibility, most adult studies use up to 2,000 to 3,000 mg per day in two or three divided doses.

Side effects:  At typical doses, there are rarely any side effects. Possible side effects at higher doses may include nausea, vomiting, abdominal cramps, diarrhea, and a “fishy” body odor.

Contraindications:  Consult your health care professional before taking Acetyl L-Carnitine if:

You have a history of seizures. L-Carnitine may make seizures more likely in people who have had seizures before.

You have hypothyroidism. L-Carnitine may make your symptoms worse.**

You are pregnant, may become pregnant, or are breastfeeding.


Acetyl-L-Carnitine is an important amino acid that promotes cellular health and energy, aids in mental focus and concentration, and may support improved insulin sensitivity for individuals deficient in L-Carnitine.


* Supplement research writer Karen Lee Richards is the Lead Expert specializing in Fibromyalgia and ME/CFS, for HealthCentral’s ChronicPainConnection. Karen is co-founder of the National Fibromyalgia Association (NFA) and was Executive Editor of Fibromyalgia AWARE magazine for four years.

** Not sure about your thyroid function? A preliminary home test might indicate a need for further investigation with your physician. According to research by Dr. Broda Barnes more than 50 years ago, taking your body temperature in the armpit the first 10 minutes after waking in the morning and before you rise can be helpful. For details, click HERE.


1.  Kuratsune H, et al. Low levels of serum acylcarnitine in chronic fatigue syndrome and chronic hepatitis type C, but not seen in other diseases. Int J Mol Med. 1998 Jul;2(1):51-6.

2. Plioplys AV, Plioplys S. Amantadine and L-Carnitine treatment of Chronic Fatigue Syndrome. Neuropsychobiology. 1997;35(1):16-23.

3.  Reuter SE, Evans AM. Long-chain acylcarnitine deficiency in patients with chronic fatigue syndrome. Potential involvement of altered carnitine palmitoyltransferase-I activity. J Intern Med. 2011 Jul;270(1):76-84.

4. Werbach M. Nutritional Strategies for Treating Chronic Fatigue Syndrome. Alt Med Rev, 2000;5(2):93-108.

5. Malaguarnera M, et al. L-Carnitine treatment reduces severity of physical and mental fatigue and increases cognitive functions in centenarians: A randomized and controlled clinical trial. Am J Clin Nutr. 2007 Dec;86(6):1738-44.

6.  Geier DA, et al. A prospective double-blind, randomized clinical trial of levocarnitine to treat autism spectrum disorders. Med Sci Monit. 2011 Jun 1;17(6):PI15-23.

7.  Mingrone G, et al. L-Carnitine improves glucose disposal in type 2 diabetic patients. J Am Coll Nutr 1999;77-82.

8.  De Grandis D, Minardi C. Acetyl-L-Carnitine (levacecarnine) in the treatment of diabetic neuropathy. A long-term, randomised, double-blind, placebo-controlled study. Drugs R D. 2002;3(4):223-31.

Note: This information has not been evaluated by the FDA. It is general information and is not intended to diagnose, prevent, treat or cure any illness, condition or disease. It is very important that you make no change in your healthcare plan or health support regimen without researching and discussing it in collaboration with your professional healthcare team.

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2 thoughts on “Breaking Through the Mental Fog”

  1. richvank says:

    I would like to note that the synthesis of carnitine in the body requires a methylation reaction. In both autism and ME/CFS, testing has shown that there is a partial block in the methylation cycle. This likely accounts for the carnitine deficits in these disorders. Taking carnitine as a supplement in these disorders can be helpful, but to restore the body’s ability to synthesize carnitine, it is necessary to lift the partial block in the methylation cycle.

    Rich Van Konynenburg, Ph.D.

  2. Sandy10m says:

    Since most ME/CFS patients are also hypothyroid (whether diagnosed or not), what do we do to avoid complicating our situations more? I know there are low-dose thyroid medications out there, but my body gets too jumpy with even the smallest amount, and my sleep is disrupted, even when only taking the thyroid meds in the morning. What do the experts recommend for us to take WITH the Carnitine to avoid the thyroid problem?

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