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Carnitine (L-Carnitine) |
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What is Carnitine (L-Carnitine): |
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Carnitine is a naturally-occurring nutrient whose main purpose is to convert fatty acids into energy, so is essential for the body's energy production. High levels of cellular energy are required for optimum health and so that your cells can repair themselves preventing premature aging. Carnitine is produced in the liver and kidneys, and is found in every cell in the body. Carnitine works as a “transporter” of the long-chain fatty acids (triglycerides/fat) into the center of the cell’s powerhouse (mitochondria). The mitochondria then convert these fatty acids into energy that is used for all activities within the body.
Carnitine deficiency can be caused by the body not being able to produce sufficent quantities, drug side effects causing depletion or a dietary deficiency. Carnitine deficiency can lead to fatigue, chest pain, muscle pain, weakness, low blood pressure, and severe mental lethargy and confusion.
Carnitine comes in many different chemical and molecular forms, with each form used for different purposes. L-carnitine, is the most commonly recommended and available form. Other common forms include Acetyl-L-Carnitine, like L Carnitine, it improves mitochondrial function, but to an even greater degree - because it can pass through the mitochondrial membrane and used mainly in the study and treatment of brain disorders; L-propionylcarnitine (LPC), used in the study and treatment of chest, heart, and vascular disorders. Not only is Carnitine responsible for the release of fat into the bloodstream for energy – it is also needed for maintenance of healthy heart tissue, muscular contractions, and the regulation of protein balance within the body. |
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History of Carnitine (L-Carnitine): |
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In the early 1900s, carnitine was discovered in a meat extract in two separate instances – once in Russia, and a year later in Germany. By 1927, the structure of carnitine was formulated and officially proposed. Twenty years later, scientists studying the nutritional needs of insects, specifically the yellow meal worm, discovered a new vitamin/nutrient critical to the growth of the worm. This vitamin was named B-T, a class of B-vitamin with the designation “T” derived from the Latin name of the yellow meal worm: Tenebrio mollitor. Vitamin B-T would later be identified as carnitine. In the late 1950s, researcher IB Fritz discovered the mechanism by which carnitine stimulates cell mitochondria to metabolize fat into energy, revealing the physiological importance of the nutrient.
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Benefits of Carnitine (L-Carnitine): |
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Carnitine supplementation has been used for the treatment of post-heart attack trauma, with studies suggesting that supplementation decreases the likelihood of a second heart attack. There is also evidence that supplementation leads to fewer abnormal heart rhythms, decreases the chance of developing congestive heart failure, lowers total cholesterol, lowers total triglyceride count, and increases HDL (“good”) cholesterol levels.
People with peripheral vascular disease are often treated with carnitine - in its L-propionylcarnitine form – helping them maintain function of their legs. Carnitine has been shown to improve visual memory and attention in individuals with Down’s Syndrome, and several studies are underway in the attempt to develop a consistent carnitine treatment for the prevention and treatment of Alzheimer’s disease.
Since the kidney is one of the two sites of carnitine production within the body, damage to the kidney can lead to carnitine deficiency. Alcohol consumption can also lead to carnitine deficiency by leading to a build-up of fat in the liver (the second site of carnitine production in the body). Supplementation is usually recommended for individuals with damaged kidneys or liver, excessive alcohol consumption, and patients undergoing hemodialysis.
To counter-act male infertility, L-carnitine supplementation has been found to increase sperm count and mobility.
Other beneficial uses of carnitine supplementation include: treatment of Chronic Fatigue Syndrome; emergency treatment of shock due to a heart attack or loss of blood; treatment of Peyronie’s Disease (scarring and blocked blood flow to the penis); and the prevention and improvement of symptoms of hyperthyroidism.
Since carnitine is essential for the efficient conversion of fat into energy, studies are currently being conducted to test carnitine’s efficacy as a fat loss and weight management supplement.
Research on this subject:
Benvenga S, Ruggeri M, Russo A, Lapa D, Campenni A, Trimarchi F. Usefulness of L-carnitine, a naturally occurring peripheral antagonist of thyroid hormone action, in iatrogenic hyperthyroidism: a randomized, double-blind, placebo-controlled clinical trial. J Clin Endocrinol Metab. 2001 Aug;86(8):3579-94.
El-Beshlawy A, Youssry I, El-Saidi S, et al. Pulmonary hypertension in beta-thalassemia major and the role of L-carnitine therapy. Pediatr Hematol Oncol. 2008 Dec;25(8):734-43.
Evans JD, Jacobs TF, Evans EW. Role of acetyl-L-carnitine in the treatment of diabetic peripheral neuropathy. Ann Pharmacother. 2008 Nov;42(11):1686-91.
Hellstrom WJ. Medical Management of Peyronie’s Disease. J Androl. 2008, Oct 30. (Ahead of print; abstract supplied by publisher).
Inazu M, Matsumiya T. Physiological functions of carnitine and carnitine transporters in the central nervous system. Nihon Shinkei Seishin Yakurigaku Zasshi. 2008;28(3):113-20.
Singh RB, Niaz MA, Agarwal P, Beegum R, Rastogi SS, Sachan DS. A randomized, double-blind placebo-controlled trial of L-carnitine in suspected acute myocardial infarction. Postgrad Med J. 1996 Jan;72(843):45-50.
Vermeulen RC, Scholte HR. Exploratory open label, randomized study of acetyl- and propionylcarnitine in chronic fatigue syndrome. Pychosom Med. 2004 Mar-Apr;66(2):276-82.
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Sources and Forms of Carnitine (L-Carnitine): |
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Within the human body, L-carnitine is synthesized in the liver and kidneys from two essential amino acids - lysine and methionin. The presence of vitamin C, niacin, B6, and iron are also essential to the synthesis of carnitine. The body produces approximately 80% of the necessary carnitine for its proper functioning, and acquires the remainder through diet.
Dietary sources of carnitine include red meat, dairy products, fish, poultry, tempeh (fermented soybeans), wheat, asparagus, avocados, and peanut butter. Miniscule amounts of carnitine are contained within fruits and vegetables.
Supplemental carnitine comes in several forms – L-carnitine, Acetyl-L-Carnitine, L-propionylcarnitine, and D-carnitine. L-carnitine is the most widely available form of supplement, and is also the one most recommended for supplementation. Other forms of carnitine are supplemented only for specific disorders, and usually under prescription and supervision of a medical professional. Under certain medical emergencies, such as shock, L-carnitine is administered in intravenous form.
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Recommended Dosage of Carnitine (L-Carnitine): |
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The body produces the majority of its needed carnitine, with the rest supplied through diet. Depending upon type of diet (read-meat based or vegetable-based), a person’s diet could include anywhere from 10 mg to 100 mg of carnitine.
Recommended doses of L-carnitine supplements for adults vary according to the condition being treated.
L-carnitine supplements to improve athletic performance and stimulate fat metabolism are usually sold as 1000 mg to 2000 mg daily doses. Sports physiologists also recommend that individuals using L-carnitine as a daily sports supplement should discontinue usage one week per month.
A daily regimen of approximately 2000 mgs of L-carnitine is suggested for the treatment of heart disease, male infertility, and the reduction of symptoms in hyperthyroidism.
Daily regimens of 2000 mgs of Acetyl-l-carnitine, or 2000 mg of L-propionylcarnitine has been used for treatment of patients with Chronic Fatigue Syndrome.
Up to 900 mg of L-carnitine daily has been used to help mediate the effects of alcohol-related carnitine deficiency.
Research on this subject:
Benvenga S, Ruggeri RM, Russo A, Lapa D, Compenni A, Trimarchi F. Usefulness of L-carnitine, a naturally occurring antagonist of thyroid hormone action, in iatrogenic hyperthyroidism: a randomized, double-blind, placebo-controlled clinical trial. J Clin Endocrinol Metab. 2001 Aug;86(8):3579-94.
Lenzi A, Lombardo F, Sgro P, Salacone P, Caponecchia L, Dondero F, Gandini L. Use of carnitine therapy in selected cases of male factor infertility: a double-blind crossover trial. Fertil Steril. 2003 Feb;79(2):292-300.
Sachan DS, Rhew TH, Ruark RA. Ameliorating effects of carnitine and its precursors on alcohol-induced fatty liver. Am J Clin Nutr. 1984;39:738-744.
Singh RB, Niaz MA, Agarwal P, Beegum R, Rastogi SS, Sachan DS. A randomized, double-blind placebo-controlled trial of L-carnitine in suspected acute myocardial infarction. Postgrad Med J. 1996 Jan;72(843):45-50.
Vermeulen RC, Scholte HR. Exploratory open label, randomized study of acetyl- and propionylcarnitine in chronic fatigue syndrome. Pychosom Med. 2004 Mar-Apr;66(2):276-82.
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Safety and Side Effects of Carnitine (L-Carnitine): |
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Carnitine does not appear to cause significant side effects, although doses higher than 5 grams per day has been known to cause diarrhea and gastric distress. Other rare side effects can include body odor, excessive appetite, and skin rash.
L-carnitine supplementation has been known to interact with medications – increasing the effectiveness of HIV drug AZT; decreasing the toxic side effects of doxorubicin, a medication used to treat cancer during chemotherapy; decreasing the negative side effect of abnormal liver function in those taking acne medication Isotretinoin; and supplementation is often required when taking the carnitine-depleting anticonvulsant medication Valproic acid.
Research on this subject:
Boonsanit D, Kanchanapangka S, Buranakari C. L-carnitine ameliorates doxorubicin-induced nephritic syndrome in rats. Nephrology (Carlton). 2006 Aug;11(4):313-20.
Butori C, Desnuelle C, Hofman P, et al. Muscular involvement in the course of AIDS. Anatomo-clinical study of 17 cases. Ann Pathol. 1995;15(6):424-30.
Chan YC, Tse ML, Lau FL. Two cases of valproic acid poisoning treated with L-carnitine. Hum Exp Toxicol. 2007 Dec;26(12):967-9.
Georgala S, Schulpis KH, Georgala C, Michas T. L-carnitine supplementation in patients with cystic acne on isotretinoin therapy. J Eur Acad Dermatol Venereol. 1999 Nov;13(3):205-9.
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Frequently Asked Questions on Carnitine (L-Carnitine): |
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Can Carnitine be used to treat heart disorders and other heart-related ailments?
Research has shown that Carnitine supplementation can be an effective treatment for individuals recovering from heart attack or surgery, but research is yet inconclusive on the ability of Carnitine to prevent heart disease.
Studies have shown that L-carnitine supplementation after heart trauma reduces the risk of a subsequent attack, reduces the occurrence of abnormal heart rhythms, and decreases the chance of developing congestive heart failure. Congestive heart failure leads to a decrease in skeletal muscle, which eventually results in increased lethargy and decreased exercise capacity.
An in vitro study showed that L-carnitine had a positive effect when applied to skeletal muscle cells, suggesting that L-carnitine supplementation may have a role in the treatment of congestive heart failure-associated myopathy.
Carnitine treated subjects showed a significant decrease in pulmonary hypertension symptoms and overall improvement in heart dimension and function during a placebo-controlled study of 32 patients with cardiac complications and pulmonary hypertension.
Research on this subject:
El-Beshlawy A, Youssry I, El-Saidi S, et al. Pulmonary hypertension in beta-thalassemia major and the role of L-carnitine therapy. Pediatr Hematol Oncol. 2008 Dec;25(8):734-43.
Jeejeebhoy F, Keith M, Freeman M, et al. Nutritional supplementation with MyoVive repletes essential cardiac myocyte nutrients and reduces left ventricular size in patients with left ventricular dysfunction. Am Heart J. 2002 Jun;143(6):1092-100.
Vescovo G, Ravara B, Gobbo V, et al. L-Carnitine: a potential treatment for blocking apoptosis and preventing skeletal muscle myopathy in heart failure. Am J Physiol Cell Physiol. 2002 Sep;283(3):C802-10.
Can Carnitine be used to delay the onset of Alzheimer’s?
Studies on the efficacy of L-carnitine usage in the treatment or prevention of Alzheimer’s has been conflicting. Studies have shown that acetyl-l-carnitine, a form of L-carnitine that readily enters the brain, may relieve symptoms of depression, as well as significantly improve visual memory and attention in those with Down’s Syndrome.
In a rat study, carnitine supplementation showed a protective effect on cortical neurons. When cells were injected with amyloid-beta peptide (the pre-cursor to the formulation of brain plaque that leads to Alzheimer’s), cell death and increased oxidative stress occurred. Pre-treatment of these cells with carnitine significantly reduced the amount of cell death. Researchers concluded that carnitine showed potential in the management of oxidative stress and neurotoxicity associated with amyloid-beta peptide presence.
However, other in vitro studies of acetyl-l-carnitine showed that its presence actually stimulated the metabolism of amyloid precursor protein. A one- year, multi-center, double-blind, placebo-controlled, randomized trial was conducted with subjects 45 to 65 years old. All subjects had been diagnosed with probable Alzheimer’s Disease, and were split into two groups of 1 gram daily acetyl-l-carnitine supplementation and placebo. After one year, the carnitine-supplemented group showed a small improvement in their Mini-Mental State Examination scores although overall, there were little or no differences in rate of decline between both groups.
Research on this subject:
Abdul HM, Calabrese V, Calvani M, Butterfield DA. Aceytl-L-carnitine induced up-regulation of heat shock proteins protects cortical neurons against amyloid-beta peptide 1-42-mediated oxidative stress and neurotoxicity: implications for Alzheimer’s disease. J. Neurosci Res. 2006 Aug 1;84(2):398-408.
Epis R, Marcello E, Gardoni F, et al. Modulatory effect of acetyl-L-carnitine on amyloid precursor protein metabolism in hippocampal neurons. Eur J Pharmacol. 2008 Nov 12;597(1-3):51-6.
Thal LJ, Calvani M, Amato A, Carta A. A 1-year controlled trial of acetyl-l-carnitine in early-onset AD. Neurology. 2000 Sep 26;55(6):805-10.
Can Carnitine be used to treat Hyperthyroidism, or alleviate the resulting symptoms of Hyperthyroidism?
Research on this matter is very promising, as multiple studies have shown positive results on supplementing with Carnitine as a Hyperthyroidism therapy. Hyperthyroidism – an imbalance whereby too much thyroid hormone is released – is a common and uncomfortable disorder that sometimes requires drastic treatment measures - including surgical removal of the thyroid gland and radioactive iodine therapy.
Prior animal studies suggestted that L-carnitine inhibited the entry of thyroid hormone into the cells of key systems. In a randomized, double-blind, 6-month placebo-controlled trial, a group of 50 women were divided into 3 groups ingesting 2 g per day, 4 grams per day of oral L-carnitine, or placebo, and were assessed to see if hyperthyroidism-related symptoms could be reversed, prevented, or minimized.
The placebo group showed worsening symptoms and biochemical parameters (TSH, T3, T4 levels), and the L-carnitine-treated groups, regardless of dose, showed marked improvements in bone mineral density. Researchers concluded that L-carnitine was effective in minimizing symptoms of hyperthyroidism, and in some cases, was able to reverse symptoms by bone re-mineralization.
In another study, the serum concentrations of carnitine and free fatty acids in the urine of both hyperthyroid and hypothyroid patients were measured. Hyperthyroid patients tend towards excretion of a greater than normal amount of carnitine – sometimes leading to carnitine deficiency. Researchers determined that there was a direct correlation between amount of serum carnitine secretion and blood-level thyroid hormones.
Research on this subject:
Benvenga S, Lapa D, Cannavo S, Trimarchi F. Successive thyroid storms treated with L-carnitine and low doses of methimazole. Am J Med. 2003 Oct 1;115(5):417-8.
Benvenga S, Ruggeri M, Russo A, Lapa D, Campenni A, Trimarchi F. Usefulness of L-carnitine, a naturally occurring peripheral antagonist of thyroid hormone action, in iatrogenic hyperthyroidism: a randomized, double-blind, placebo-controlled clinical trial. J Clin Endocrinol Metab. 2001 Aug;86(8):3579-94.
Famularo G, De Simone C, Trinchieri V, Mosca L. Carnitines and its congeners: a metabolic pathway to the regulation of immune response and inflammation. Ann NY Acad Sci 2004 Nov;1033:132-8.
Maebashi M, Kawamura N, Sato M, Imamura A, Yoshinaga K. Urinary excretion of carnitine in patients with hyperthyroidism and hypothyroidism: augmentation by thyroid hormone. Metabolism. 1977 Apr;26(4):351-6.
Sugden MC, Holness MJ, Liu YL, Smith DM, Fryer LG, Kruszynska YT. Mechanisms regulating cardiac fuel selection in hyperthyroidism. Biochem J. 1992 Sept 1;286(Pt 2):513-7.
Sugden MC, Priestman DA, Orfall KA, Holness MJ. Hyperthyroidism facilitates cardiac fatty acid oxidation through altered regulation of cardiac carnitine palmitoyltransferase: studies in vivo and with cardiac myocytes. Horm Metab Res. 1999 May;31(5):300-6.
My bodybuilding buddy at the gym tells me that L-carnitine supplementation is essential for enhancing your performance when working out. Is this really true?
While several studies show strong evidence that L-carnitine helps the body metabolize fat, strengthens the heart, and increases bone density – the studies on L-carnitine supplementation in healthy individuals has been inconclusive.
Animal studies showed positive results for L-carnitine supplementation. Aged rats were supplemented with 30 mg per kg of body weight daily for 12 weeks. At the end of the study, the rats showed improved L-carnitine levels in muscle cells, restored oxidative activity in lower extremities, and an improved body ratio of muscle to fat – all without any changes in diet.
In another rat study, scientists examined the effects of carnitine supplementation while chemically mimicking symptoms human heart trauma within the rats. Carnitine supplementation led to worsening of the tissue injury and a slower recovery rate in contractile function, as compared to the control group.
A human study evaluated the effects of L-carnitine L-tartrate supplementation on muscle tissue oxygenation during and after multiple sets of squat exercise. Measuring amount of muscle oxygenation, the results showed a positive outcome (decreased plasma membrane damage) and a negative outcome (reduced oxygenation) of carnitine supplementation.
Results of many other studies on the exercise (resistance and aerobic) effects of L-carnitine supplementation have also been conflicting.
Research on this subject:
Bernard A, Rigault C, Mazue F, Le Borgne F, Demarquoy J. L-carnitine supplementation and physical exercise restore age-associated decline in some mitochondrial functions in the rat. J Gerontol A Biol Sci Med Sci. 2008 Oct;63(10):1027-33.
Diaz R, Lorita J, Soley M, Ramirez I. Carnitine worsens both injury and recovery of contractile function after transient ischemia in perfused rat heart. J Physiol Biochem. 2008 Mar;64(1):1-8.
Spiering BA, Kraemer WJ, Hatfield DL, et al. Effects of L-carnitine supplementation on muscle oxygenation responses to resistance exercise. J Strength Cond Res 2008 Jul:22(4):1130-5.
Can L-carnitine supplementation help me burn fat and lose weight?
Since the main function of carnitine is to transport fatty acids into mitochondria for oxidation - carnitine is often purported to increase fat-burning ability. Unfortunately the research is not 100% conclusive, both animal and human studies show no conclusive evidence as to the efficacy of carnitine supplementation for burning fat. However, optimal Carnitine levels are required for optimal fat burning efficiency.
In one study, adult female hogs supplemented with L-carnitine showed a greater reduction of back-fat thickness during lactation, demonstrating an enhancement in body fat mobilization.
In a separate study, rats were fed an energy-deficient diet, and then divided into an L-carnitine supplemented group and a placebo group. After 23 days, there were no significant positive effects of L-carnitine supplementation on weight loss and body composition, and there were no significant differences between the supplemented and non-supplemented groups.
Human studies also show mixed results. In a frequently reviewed experiment, 18 subjects were split into a placebo group and a 2 gram daily L-carnitine-supplemented group. After 12 weeks, the average weight loss in the placebo group was one pound, while the average weight loss in the L-carnitine-supplemented group was 11 pounds. Body fat percentages were also markedly decreased in the L-carnitine group.
An opposing study revealed no significant changes in body composition, resting energy expenditure, and fat mobilization in either the 4 gram daily L-carnitine supplemented group or the placebo group.
Research on this subject:
Avogaro P, Bon GB, Cazzolato G, Rorai E. Acute effects of L-carnitine on FFA and Beta-OH-Butyrate in Man. Pharmacol Res Commun.I 1981;13(5):443-50.
Brandsch C, Eder K. Effect of L-carnitine on weight loss and body composition of rats fed a hypocaloric diet. Ann Nutr Metab. 2002;46(5):205-10.
Ramanau A, Kluge H, Eder K. Effects of L-carnitine supplementation on milk production, litter gains and back-fat thickness in sows with a low energy and protein intake during lactation. Br. J Nutr. 2005 May;93(5):717-21.
Rebouche CJ, Paulson DJ. Carnitine Metabolism and Function in Humans. Ann Rev Nutr. 1996;6:41-66.
Villani RG, Gannon J, Self M, Rich PA. L-Carnitine supplementation combined with aerobic training does not promote weight loss in moderately obese women. Int J Sport Nutr Exerc Metab. 2000 Jun;10(2):199-207.
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Additional Research on Carnitine (L-Carnitine): |
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Carnitine and Alzheimer's
Hino K, Nishikawa M, Sato E, Inoue M. L-carnitine inhibits hypoglycemis-induced brain damage in the rat. Brain Res. 2005 Aug 16;1053(1-2):77-87.
Kidd PM. Alzheimer’s disease, amnestic mild cognitive impairment and age-associated memory impairment: current understanding and progress toward integrative prevention. Altern Med Rev. 2008 Jun;13(2):85-115.
Pueschel SM. The effect of acetyl-L-carnitine administration on persons with Down Syndrome. Res Dev Disabil. 2006 Nov-Dec;27(6):599-604.
Carnitine and Exercise Performance
Eroglu H, Senel O, Guzel NA. Effects of acute L-carnitine intake on metabolic and blood lactate levels of elite badminton players. Neuro Endocrinol Lett. 2008 Apr;29(2):261-6.
Kraemer WJ, Volek JS, French DN, et al. The effects of L-carnitine L-tartrate supplementation on hormonal responses to resistance exercise and recovery. J Strength Cond Res. 2003 Aug;17(3):455-62.
Stuessi C, Hofer P, Meier C, Boutellier U. L-Carnitine and the recovery from exhaustive endurance exercise: a randomized, double-blind, placebo-controlled trial. Eur J Appl Physiol. 2005 Dec;95(5-6):431-5.
Volek JS, Kraemer WJ, Rubin MR, Gomez AL, Ratamess NA, Gaynor P. L-Carnitine L-tartrate supplementation favorably affects markers of recovery from exercise stress. Am J Physiol Endocrinol Metab. 2002 Feb;282(2):E474-82.
Carnitine and Weight Loss
Aja S, Landree LE, Kleman AM, et al. Pharmacological stimulation of brain carnitine palmitoyl-transferase-1 decreases food intake and body weight. Am J Physiol Requl Integr Comp Physiol. 2008 Feb;294(2):R352-61.
Elmslie JL, Porter RJ, Joyce PR, Hunt PJ, Mann JI. Carnitine does not improve weight loss outcomes in valproate-treated bipolar patients consuming an energy-restricted low-fat diet. Bipolar Disord. 2006 Oct;8(5 Part 1):503-7.
Foster DW. The role of the carnitine system in human metabolism. Ann N Y Acad Sci. 2004 Nov;1033:1-16.
Johnston CS, Corte C, Swan PD. Marginal vitamin C status is associated with reduced fat oxidation during submaximal exercise in young adults. Nutr Metab (Lond). 2006 Aug 31;3:35.
Karlic H, Lohninger A. Supplementation of L-carnitine in athletes: does it make sense? Nutrition. 2004 Jul-Aug;20(7-8):709-15.
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