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Acetyl L Carnitine

Review of Acetyl L Carnitine

What is Acetyl-L-Carnitine?

Acetyl-l-carnitine (ALC) is the acetylated form of L-carnitine. It is responsible for the transport of long chain fatty acids into the mitochondria for use as fuel in aerobic respiration. Supplementation with Acetyl-L-Carnitine is believed to lead to enhanced fatty acid metabolism. Acetyl L Carnitine acts as a powerful antioxidant and is known to detoxify some of the waste products of metabolism including ammonia. It is has very similar metabolic effects as l-carnitine but has a greater level of bioavailability - it is transported more easily into the blood stream, passes more freely into the mitochondria, can cross the blood brain barrier and has a greater work rate than L-carnitine. Acetyl-l-carnitine is a naturally occuring substance that is found in small quantities in our diets, and is produced naturally in our body in small quantities. The human body is able to produce 20% of its L-carnitine needs from the essential amino acids methionine and lysine. Acetyl-L-Carnitine can be produced by the conversion of L-Carnitine and acetyl-CoA within the mitochondria. Acetyl-l-carnitine is required in larger amounts during prolonged exercise.

Who Should Consider Taking L Carnitine?

Acetyl-L-Carnitine has a number of benefits for anyone involved in intense or prolonged exercise. Anyone on a low calorie, who is vegetarian or on a low meat diet, or who trains intensively and for prolonged periods of timemay be prone to deficiencies in carnitine.  L-Carnitine/Acetyl-L-carnitine is known to be important for endurance athletes as its main function is to transport fatty acids inside the mitochondria (energy powerhouses within muscle cells) where energy is produced aerobically by the oxidation of the fatty acids.  However, Acetyl-L-Carnitne is believed to have greater bioavailability than non acetylated carnitine and passes more easily into the blood stream, and the mitochondria, where it has a greater work rate than L-carnitine.  Research has also shown ALC to be more effective than L-carnitine (Hiat, 2004).  Acetyl-L-Carnitine/l-carnitine supplementation is also believed to increase the use of fat for energy and therefore may be beneficial to people looking to loose weight. It has also been shown to have a number of health benefits.

Summary of Acetyl-L-Carnitine's Phyiological Effects:

  • Acetyl-L-Carnitine increases transport of fatty acids into the mitochondria for use in aerobic respiration
  • Improved blood flow and delivery of oxygen to working muscles
  • Acetyl-L-Carnitine reduces muscle damage and muscle soreness
  • Helps to improve the rate of recovery following strenuous exercise
  • Acetyl-L-Carnitine acts as a powerful antioxidant, and helps to detoxify the waste products of metabolism
  • Helps to maintain normal testosterone levels during periods of intense physical or mental stress
  • Acetyl-L-Carnitine appears to be particularly beneficial to endurance athletes with heavy training loads
  • The positive cardiovascular effects can last up to 60 days after treatment
  • Acetyl-L-Carnitine has a neuroprotective effect, improves mental function, alertness, and memory
  • Believed to enhance fat metabolism and may be beneficial for weight loss
  • Acetyl-L-Carnitine appears to have a positive effect on heart health and function, and has proved effective in the treatment of cardiac patients
  • Appears to be safe with no serious side effects

Acetyl-L-Carnitine Research

Acetyl-L-Carnitine, Heart Function, and Fatty Acid Transport

L-carnitine/Acetyl-l-carnitine plays a central role in lipid metabolism by transporting long chain fatty acids into the mitochondria for use as a fuel in aerobic metabolism. Dietary supplementation of L-carnitine is known to improve fat utilization (Ramsay 2000) and has a protective effect on the heart (Amin and Nagy, 2009; Loster et al., 1993; Malone et al., 2006;) and blood vessels (Hulsmann and Duebaar, 1988; Hiatt, 2004). Supplementation with L-Carnitine has even been shown to be beneficial to patients with chronic heart disease where it reduced the incidence of chronic heart failure and death (Iliceto et al., 1995). Carnitine supplementation can increase blood flow, and therefore enhance oxygen delivery, to the heart and working muscles (Kraemer and Volek, 2000). This effect is mainly attributable to carnitines ability to increase vasodilatation (Amin and Nagy 2009) which may be caused by an increased production of nitric oxide, and maintenance of existing nitric oxide by acetyl-l-carnitine (Bloomer 2009). Acetyl-l-carnitines ability to improved blood supply during exercise may enhance exercise performance, improvements in blood supply may also enhance post exercise recovery.

Acetyl-L-Carnitine and Brain Health

Acetyl-L-Carnitine has been shown to have a number of positive effects on brain health, including: a neuroprotective effect (Flanagan et al., 2010; Traina et al., 2010), improved mental function, alertness, reduced depression, improved memory, and reduced levels of age associated decline in brain function (Cipolli and Chiari, 1990; Tempesta et al., 1990; Liu et al., 2002; McDaniel et al., 2003), and is particularly effective when combined with alpha lipoic acid (Liu et al.,2003). Acetyl-L-Carnitine acts as a general brain energizer by helping to maintain a constant supply of energy needed for normal brain function (Kidd, 1998; Kidd, 1999). 

Acetyl-L-Carnitine, Antioxidant status, and Ammonia removal

Acetyl-L-Carnitine/l-carnitine is known to have good antioxidant activity (Amin and Nagy, 2009; Gülçin I. 2006) and has the ability to detoxify ammonia, a metabolic by-product associated with early fatigue (Kanter and Williams, 1995). The ability of acety-l-carnitine to detoxify metabolic waste products and protect against the cell damaging effects of free-radicals may contribute to the beneficial effects seen when ALC is taken by endurance athletes.

Acetyl-L-Carnitine and Weight Loss

Acetyl-L-Carnitine/L-Carnitine appears to be a beneficial supplement for treating obesity/weight loss (Amin & Nagy 2009; Cave et al., 2008). Animal studies have demonstrated that carnitine supplementation can improve glucose tolerance, increase total energy expenditure (Cave et al., 2008) reduce body weight, improve the lipid profile and glucose levels, reduce insulin resistance and oxidative stress markers (Amin & Nagy 2009). These research studies demonstrate that Acetyl-L-Carnitine/L-Carnitine may be beneficial for weight loss, Obesity and type II diabetes. 

Acetyl-L-Carnitine/L-Carnitine and Liver Function

Evidence is mounting that Acetyl-L-carnitine/L-Carnitine may have a beneficial protective effect on Cirrohsis and Liver disorders (Amin & Nagy 2009; Cave et al., 2008; Flanagan et al., 2010). Carnitine also appears to be effective at preventing lipid accumulation within the Liver (Sachan et al., 1984; Flanagan et al., 2010)

Acetyl-L-Carnitine and Intense Training

Research shows that carnitine levels can fall dramatically with exercise (Hiatt et al 1989) and as such L-carnitine has become a popular supplement for endurance athletes during periods of intense training (Neumann et al., 2000). Research has shown that supplementing with 1g of carnitine a day can help to protect against reductions in muscle carnitine levels during periods of increased training volume or increased intensity (Giamberardino et al., 1996). Improved recovery following L-carnitine supplementation is also supported by Volek et al., 2002, who demonstrated reduced: markers of muscle damage, reduced tissue damage, reduced muscle soreness as well as reduced levels of free radical damage. Supplementation of 2g of L-Carnitine has been demonstrated to reduce levels of muscle damage (Jeff et al 2002; Kraemer et al., 2003). Both of these research teams suggested that Carnitine supplementation may be particularly effective at improving the rate of recovery. There appears to be very clear evidence that L-carnitine supplementation has beneficial effects on training, competition, and recovery from strenuous training (Karlic and Lohminger, 2004). In this way Acetyl-L-Carnitine helps athletes to tolerate greater training loads, and therefore gives athletes the potential to train at higher levels with a reduced risk of overtraining.

One particularly promising aspect of L-carnitine supplementation is that it may have a long term positive effect that lasts beyond the supplementation period. Research looking at the positive effects of L-carnitine supplementation on cardiac patients found that exercise performance was still improved 60 days after supplementation was stopped (Loster et al., 1999). Therefore, you may still get a positive benefit from L-carnitine even when you have stopped taking it.

Acetyl-L-Carnitine and Testosterone Levels

As well as producing all of the physiological benefits described above, Acetyl-L-Carnitine has some additional benefits that won’t occur with plain L-carnitine supplemetation. Bidzinska et al., 1993, demonstrated that Acetyl-L-Carnitine supplementation helps to prevent a drop in testosterone production following periods of physical or mental stress. Further studies (Krsmanovic et al., 1994) have also demonstrated that Acetyl-L-Carnitine supplementation promotes the growth and activity of cells in the brain responsible for producing hormones that activate testosterone production. Acetyl-L-Carnitine may therefore help athletes to cope more effectively with the high levels of physical and mental stress associated with large training volumes. 

Is Acetyl-L-Carnitine effective?

Acetyl-L-Carnitine appears to be effective at enhancing the rate of recovery from exercise, reducing muscle soreness, improving heart function, enhancing brain function, and speeding up the transport of fatty acids into the mitochondria.

How to take Acetyl-L-Carnitine?

The general recommendation for acetyl-l-carnitine/l-carnitine supplementation is 1-2g per day during periods of intensified training (Neumann et al., 2000).  It is generally recommended that this is taken on an empty stomach in the morning or early afternoon – try not to take Acetyl-L-Carnitine too late in the evening as it may make you feel more alert and therefore make it harder to sleep.  High doseages should be avoided as the excess is likely to be excreted and therefore wasted.  When training load is reduced, acetyl-l-carnitine/L-carnitine intake should be stopped.  This is important, particularly when taking larger doses as it helps to ensure that the body's own production of acetyl-l-carnitine/L-carnitine is not disrupted and remains active.

For general health benefits it is normally recommended to take 250mg-1,000mg daily of Acetyl-L-Carnitine.

There is insufficient evidence to provide recommendations for the best dose of ALC for weight management/weight loss, however it most commonly taken at between 1,000mg-3,000mg daily in divided doses.

Acetyl-L-Carnitine Side Effects

Acetyl-L-Carnitine/L-Carnitine is non-toxic and appears to be free of side effects when taken at doses of up to 6g daily.

Acetyl-L-Carnitine References

Amin K. A. and A Nagy, M. A. (2009) Effect of Carnitine and herbal mixture extract on obesity induced by high fat diet in rats. Diabetology & Metabolic Syndrome, 1:17

Bidzinska, B., Petraglia, F., Angioni, S., Genazzani, A. D., Criscuolo, M., Ficarra, G., Gallinelli, A., trentini, G. P. and Genazzani, A. R. (1993) Effect of different chronic intermittent stressors and acetyl-l-carnitine on hypothalmic beta-endorphin and GnRH on plasma testosterone levels in male rats. Neuroendocrinology. 57, 985-990.

Bloomer R. J., Fisher-Wellman K. H. and Tucker P. S. (2009) Effect of oral acetyl L-carnitine arginate on resting and postprandial blood biomarkers in pre-diabetics. Nutrition & Metabolism, 6:25

Cave MC, Hurt RT, Frazier TH, Matheson PJ, Garrison RN, McClain CJ, McClave SA (2008) Obesity, inflammation, and the potential application of pharmaconutrition. Nutr Clin Pract 2008, 23:16-34.

Cipolli, C. and Chiari, G. (1990) Effects of L-acetylcarnitine on mental deterioration in the aged: initial results. Clin Ter. 132 (6 suppl), 479-510.

Flanagan JL, Simmons PA, Vehige J, Willcox MDP, Garrett Q (2010) Role of carnitine in disease. Nutrition & Metabolism 2010, 7:30.

Giamberardino, m. A., Dragani, L., Valente, r., Di Lisa, F., Saggini, R. and Vecchiet, L. (1996) Effects of prolonged L-carnitine administration on delayed muscle pain and CK release after eccentric effort. International Journal of Sports Medicine. 17, 320-324.

Gülçin I. (2006) Antioxidant and antiradical activities of L-carnitine.Life Sci. Jan 18;78(8):803-11.

Hiatt W. R., Regensteiner J. G., Wolfel E. E., Ruff L. and Brass E. P. (1989) Carnitine and acylcarnitine metabolism during exercise in humans. Dependence on skeletal muscle metabolic state. J Clin Invest. October; 84(4): 1167–1173.

Hiatt, W. R. (2004) Carnitine and peripheral arterial disease. Ann N Y Acad Sci. 1033, 92-98.

Hulsmann, W. C. and Dubelaar, M. L. (1988) Aspects of fatty acid metabolism in vascular endothelial cells. Biochemie. 70, 681-686.

Iliceto S, Scrutinio D, Bruzzi P, D'Ambrosio G, Boni L, Di Biase M, Biasco G, Hugenholtz PG, Rizzon P (1995) Effects of L-carnitine administration on left ventricular remodeling after acute anterior myocardial infarction: the L-Carnitine Ecocardiografia Digitalizzata Infarto Miocardico (CEDIM) Trial. J Am Coll Cardiol 1995, 26:380-387.

Kanter, M. N. and Williams, M. H. (1995). Antioxidants, carnitine, and choline as putative ergogenic aids. International Journal of Sports Nutrition. 5, S120-S131.

Karlic, H. and Lohminger, A. (2004) Supplementation of L-carnitine in athletes: does it make sense? Nutrition. 20 (7-8), 709-715.

Kidd, P. M. (1998) Phosphatidylserine (PS), A remarkable Brain Cell Nutrient. Decatur, IL: Lucas Meyer, Inc.

Kidd, P. M. (1999) A Review of Nutrients and Botanicals in the Integrative Management of Cognitive Dysfunction. Alternative Medicine Review. 4 (3), 144-161.

Kraemer, W. J. and Volek, J. S. (2000) L-carnitine supplementation for the athlete. Anew perspective. Annals of Nutrition and Metabolism. 44, 88-89.

Kramer, W. J., Volek, J. S., French, D. N., Rubin, M. R., Sharman, M. J., Gomez, A. L., Ratamess, N. A., Newton, R. U., Jemiolo, B., Craig, B. W. and Hakkinen, K. (2003) The effects of L-carnitine L-tartrate supplementation on hormonal responses to resistance exercise and recovery. J Strength Cond Res. 17 (3), 455-462.

Krsmanovic, L. Z., Virmani, M. a., Stojilkovic, S. S. and Catt, K. J. (1994) Stimulation of gonadotrophin-releasing hormone secretion by acetyl-l-carnitine in hypothakmic neurons and GT1 neuronal cells. Neuroscience Letters. 165, 33-36.

Liu, J., Head, E., Gharib, A. M., Yuan, W., Ingersoll, R. T., Hagen, T. M., Cotman, C. W. and Ames, B. N. (2002) 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. Neurobiology. 99 (4), 2356-2361.

Loster, H., Miehe, K., Punzel, M., Stiller, O., Pankau, H. and Schauer, J. (1999) Prolonged oral L-carnitine substitution increases bicycle ergometer performance in patients with severe, ischemically induced cardiac insufficiency. Cardiovascular Drugs Therapy. 13, 537-546.

Malone JI, Cuthbertson DD, Malone MA, Schocken DD (2006) Cardio-protective effects of carnitine in streptozotocin-induced diabetic rats. Cardiovascular Diabetology 2006, 5:2

McDaniel, M. A., Maier, S. F. and Einstein, G. O. (2003) “Brain-specific” nutrients: a memory cure? Nutrition. 11-12, 955-956.

Neumann, G., Pfutzner, A. and Berbalk, A. (2000). Successful Endurance Training. Oxford: Meyer and Meyer Sport (UK), LTD.

Ramsay R R (2000) The carnitine acyltransferases: modulators of acyl-CoA-dependent reactions. Biochem Soc Trans , 28(2):182-6.

Sachan DS, Rhew TH, Ruark RA: (1984) Ameliorating effects of carnitine and its precursors on alcohol-induced fatty liver. Am J Clin Nutr 1984, 39:738-744.

Tempesta, E., Troncon, R., Janiri, L., et al., (1990) Role of acetyl-L-carnitine in the treatment of cognitive deficit in chronic alcoholism. Int J Clin Pharmacol Res. 10, 101-107.

Traina G, Bernardi R, Cataldo E, Macchi M, Durante M, Brunelli M (2008) In the Rat Brain Acetyl-L: -carnitine Treatment Modulates the Expression of Genes Involved in Neuronal Ceroid Lipofuscinosis. Mol Neurobiol 2008. 38(2):146-52.

Volek, J. S., Kraemer, W.J., Rubin, M. R., Gomez, A. L., Ratamess, N. A. and Gaynor, P. (2002) L-carnitine L-tartrate supplementation favouably affects markers of recovery from exercise stress. American Journal of Physiology. 282, E474-482.