Acetyl-L-Carnitine (ALC)

Overview

Acetyl-L-carnitine (ALC) is the acetylated ester of the amino acid L-carnitine. ALC is produced naturally in humans, with the greatest amounts being found in muscles, the brain, and in male testicles. ALC facilitates the production of energy from long chain fatty acids.

Acetyl-L-carnitine is considered to be a cognitive enhancing nutrient because it increases the production and release of acetylcholine in the brain. ALC has become recognized as an important nutrient in the prevention of brain aging. It is a neuroprotective agent and results from animal studies indicate that ALC can reverse hippocampal and prefrontal neuronal loss and lipofuscin accumulation in aged animals. As people and animals age, there is a decline in the production of Nerve Growth Factor (NGF) and in the number of NGF receptors. It has been discovered that acetyl-L-carnitine may slow down and partially reverse both of these negative consequences of the aging process. (1)

In another study it was demonstrated that acetyl-L-carnitine reverses the age-related decline in mitochondrial pyruvate metabolism in the heart by restoring the normal cardiolipin content. Cardiolipin is a critical phospholipid that facilitates the transport of substrates across mitochondrial membranes. It was discovered that the cardiolipin content in the heart of aged rats had declined by approximately 40%. Administration of acetyl-L-carnitine to aged rats resulted in almost complete restoration of cardiolipin levels and mitochondrial pyruvate metabolism to the level of young control rats. (2) Future research in this area could determine if acetyl-L-carnitine may be able to provide beneficial effects on the aging process.

Dosage Info

Dosage Range

500-2,500mg daily.

Most Common Dosage

500mg, 2 times a day.

Dosage Forms

Capsules and tablets.

Adult RDI

None established

Adult ODA

None established

RDA

  • : None established

Active Forms

Acetyl-L-carnitine.

Absorption

Animal studies indicate that acetyl-L-carnitine is readily absorbed intact from the jejunum area of the small intestine.

Toxicities & Precautions

General

There is no known toxicity associated with acetyl-L-carnitine.

Side Effects

A few people have reported mild nausea and vomiting. (3) One study reported that taking acetyl-L-carnitine at night caused nighttime sleeplessness in some patients and suggested that doses of this nutrient be taken in the morning to avoid this possible problem.

Functions in the Body

Acetyl Donor

Provides acetyl groups for the production of acetyl-Coenzyme A from free coenzyme A.

Neurotransmitter

Enhances the synthesis and release of the neurotransmitter acetylcholine in several areas of the brain such as the striatum and hippocampus.

Improve Memory

Reported to help improve memory, attention span, and mental performance in normal individuals as well as those with cognitive impairment.

Energy Production

Helps transport long-chain fatty acids across cellular membranes into the mitochondria where they are used in the production of energy.

Sperm Maturation

Plays a role in the maturation and mobility of sperm within the male reproductive tract, specifically the mobility of the sperm.

Clinical Applications

Fatigue

Results from 2 studies have suggested that ALC was effective in improving fatigue and was well tolerated. (4) , (5)

Alzheimer's Disease

Several studies report that acetyl-L-carnitine can slow the rate of progression of Alzheimer’s disease. (6) , (7) However in another recent study, Alzheimer’s disease patients treated for one year with ALC gained very little benefit. (8)

Alcoholism

Animal studies have demonstrated that the administration of acetyl-L-carnitine reduces the metabolic abnormalities that occur with ethanol exposure, which suggest that acetyl-L-carnitine may be useful in the prevention of alcohol-induced cellular damage. (9) , (10) In another study, it was demonstrated that acetyl-L-carnitine significantly reduced the onset of tremors associated with ethanol withdrawal syndrome. This suggests that acetyl-L-carnitine may be useful in the treatment of alcohol dependence. (11)

Cognitive Enhancement

Two studies were completed in rats evaluating the use and impact of acetyl-L-carnitine (ALC) and/or (R) – lipoic acid (LA). One study evaluated the association of brain mitochondrial decay and RNA/DNA oxidation to memory loss. The test group taking the combination of the two products improved memory in both spatial memory and temporal memory. The results suggest that feeding ALC and/or LA to old rats improved memory performance by lowering oxidative damage to nucleic acids and improving mitochondrial function by reversing age-associated structural decay. (12) The second study indicated improved mitochondrial-supported cellular metabolism and lowered oxidative stress. (13) Both studies showed that the combination of ALC and LA were more effective than either supplement alone.

Studies report that therapy with ALC can result in improved cognitive abilities in Alzheimer’s disease patients (14) and in alcoholics. (15)

Diabetes

Acetyl-L-carnitine increases nerve conduction velocity and decreases peripheral neuropathy in diabetic patients. (16)

Cataracts

In an animal model, the administration of acetyl-L-carnitine resulted in a 42% reduction in glycation of lens crystallins and a 70% reduction in advanced glycation end products (AGEs). These improvements suggest that acetyl-L-carnitine may be helpful in the prevention of cataracts. (17)

Depression

In elderly patients with depression, acetyl-L-carnitine produced significant reduction in depression and significant improvement in quality of life measurements. (18)

Peyronie's Disease

In a study comparing tamoxifen and acetyl-L-carnitine, ALC was significantly more effective at inhibiting disease progression in patients with acute and early chronic Peyronie's disease. ALC caused a significant reduction in penile curvature, but tamoxifen did not; (19) and both agents significantly reduced plaque size.

Symptoms and Causes of Deficiency

Acetyl-L-carnitine is naturally produced in the human body, and to date, no specific condition has been identified with a deficiency of ALC. However, based on what is known about acetyl-L-carnitine’s functions in the body, it could be speculated that a deficiency could result in decreased energy production, elevated blood lipids, cognitive decline, and an increased rate of aging in various parts of the neuroendocrine system.

Dietary Sources

Small amounts of acetyl-L-carnitine occur naturally in the muscle tissue, brain, and other organs of animals, but the amounts are not sufficient to be able to provide therapeutic levels of this nutrient.

References

  1. View Abstract: Taglialatela G, et al. Stimulation of Nerve Growth Factor Receptors in PC12 by Acetyl-L-carnitine. Biochem Pharmacol. Aug1992;44(3):577-85.
  2. View Abstract: Paradies G, Petrosillo G, Gadaleta MN, Ruggiero FM. The effect of aging and acetyl-L-carnitine on the pyruvate transport and oxidation in rat heart mitochondria. FEBS Lett. Jul1999;454(3):207-9.
  3. View Abstract: Rai G, Wright G, Scott L. Double-blind, placebo controlled study of acetyl-l-carnitine in patients with Alzheimer's dementia. Curr Med Res Opin. 1990;11(10):638-647.
  4. View Abstract: Vermeulen RC, Scholte HR. Exploratory open label, randomized study of acetyl- and propionylcarnitine in chronic fatigue syndrome. Psychosom Med. Mar2004;66(2):276-82.
  5. View Abstract: Tomassini V, Pozzilli C, Onesti E, et al. Comparison of the effects of acetyl L-carnitine and amantadine for the treatment of fatigue in multiple sclerosis: results of a pilot, randomised, double-blind, crossover trial. J Neurol Sci. Mar2004;218(1-2):103-8.
  6. View Abstract: Brooks JO 3rd, et al. Acetyl-L-carnitine Slows Decline in Younger Patients with Alzheimer's Disease: A Reanalysis of a Double-blind, Placebo-controlled Study Using the Trilinear Approach. Int Psychogeriatr. Jun1998;10(2):193-203.
  7. View Abstract: Spagnoli A, et al. Long-term Acetyl-L-carnitine Treatment in Alzheimer's Disease. Neurology. Nov1991;41(11):1726-32.
  8. View Abstract: Thal LJ, Calvani M, Amato A, Carta A. A 1-year controlled trial of acetyl-l-carnitine in early-onset AD. Neurology. Sep2000;55(6):805-10.
  9. View Abstract: Calabrese V, Scapagnini G, Catalano C, et al. Effects of acetyl-L-carnitine on the formation of fatty acid ethyl esters in brain and peripheral organs after short-term ethanol administration in rat. Neurochem Res. Feb2001;26(2):167-74.
  10. View Abstract: Sbriccoli A, Carretta D, Santarelli M, et al. An optimised procedure for prenatal ethanol exposure with determination of its effects on central nervous system connections. Brain Res Brain Res Protoc. Jan1999;3(3):264-9.
  11. View Abstract: Mangano NG, Clementi G, Costantino G, et al. Effect of acetyl-L-carnitine on ethanol consumption and alcohol abstinence syndrome in rats. Drugs Exp Clin Res. 2000;26(1):7-12.
  12. View Abstract: Liu J, Head E, Gharib AM, Yuan W, Ingersoll RT, Hagen TM, et al. Memory loss in old rats is associated with brain mitochondrial decay and RNA/DNA oxidation: Partial reversal by feeding acetyl-L-carnitine and/or R-alpha -lipoic acid. Proc Natl Acad Sci U S A. Feb2002;99(4):2356-2361.
  13. View Abstract: Hagen TM, Liu J, Lykkesfeldt J, Wehr CM, Ingersoll RT, Vinarsky V, et al. Feeding acetyl-L-carnitine and lipoic acid to old rats significantly improves metabolic function while decreasing oxidative stress. Proc Natl Acad Sci U S A. Feb2002;99(4):1870-1875.
  14. View Abstract: Passeri M, et al. Acetyl-L-carnitine in the Treatment of Mildly Demented Elderly Patients. Int J Clin Pharmacol Res. 1990;10(1-2):75-79.
  15. View Abstract: Tempesta E, et al. Role of Acetyl-L-carnitine in the Treatment of Cognitive Deficit in Chronic Alcoholism. Int J Clin Pharmacol Res. 1990;10(1-2):101-07.
  16. View Abstract: Lowitt S, et al. Acetyl-L-carnitine Corrects the Altered Peripheral Nerve Function of Experimental Diabetes. Metabolism. May1995;44(5):677-80.
  17. View Abstract: Swamy-Mruthinti S, Carter AL. Acetyl- L -carnitine decreases glycation of lens proteins: in vitro studies. Exp Eye Res. Jul1999;69(1):109-15.
  18. View Abstract: Bella R, et al. Effect of Acetyl-L-carnitine on Geriatric Patients Suffering from Dysthymic Disorders. Int J Clin Pharmacol Res. 1990;10(6):355-60.
  19. View Abstract: Biagiotti G, Cavallini G. Acetyl-L-carnitine vs tamoxifen in the oral therapy of Peyronie's disease: a preliminary report. BJU Int. Jul2001;88(1):63-7.