What is L-Carnitine?
This post was written with Consensus AI Academic Search Engine – please read our Disclaimer at the end of this article. L-Carnitine is a naturally occurring compound that plays a crucial role in the metabolism of fatty acids. It is synthesized endogenously in the human body and can also be obtained from dietary sources. This compound is essential for the transport of long-chain fatty acids into the mitochondria, where they undergo β-oxidation to produce energy. L-Carnitine has been studied extensively for its potential therapeutic benefits in various health conditions, including cardiovascular diseases, obesity, dyslipidemia, fatigue, and insulin resistance. Other names include: 3-carboxy-2-hydroxy-N,N,N-trimethyl-1-propanaminium inner salt, (3-carboxy2-hydroxypropyl) trimethylammonium hydroxide inner salt, 3-hydroxy-4-N-trimethylaminobutyrate, Aminocarnitine, B-hydroxy-N-trimethyl aminobutyric acid, Beta-hydroxy-gamma-trimethylammonium butyrate, Beta-hydroxyl-gamma-tributyl aminobutyrate, B(t) Factor, Carnitine, Carnitine Orotate, Carnitor, D-Carnitine, DL-Carnitine, Facteur B(t), L-3-hydroxy-4-(trimethylammonium)-butyrate, Levocarnitine, Lévocarnitine, Levocarnitine Fumurate, L-b-hydroxy-c-N-trimethylaminobutyric acid, L-Carnitina, L-Carnitine Fumarate, L-Carnitine L-Tartrate, L-Carnitine Tartrate, (R)-(3-carboxy-2-hydroxypropyl) trimethylammonium hydroxide, (R)-3-hydroxy-4-trimethylammonio-butyrate, Vitacarn, Vitamin B(t), Vitamine B(t).
Uses of L-Carnitine
Role in Fatty Acid Metabolism
L-Carnitine acts as a cofactor for several enzymes involved in the transport of fatty acids into the mitochondrial matrix. These enzymes include carnitine translocase and acylcarnitine transferases I and II. The primary function of L-Carnitine is to facilitate the conversion of free long-chain fatty acids into acylcarnitines, which can then be transported into the mitochondria for β-oxidation. This process is essential for energy production, especially in tissues that rely heavily on fatty acid oxidation, such as skeletal and cardiac muscle7 10.
Cardiovascular Health
L-Carnitine has shown promising results in the secondary prevention of cardiovascular diseases. A systematic review and meta-analysis revealed that L-Carnitine supplementation significantly reduced all-cause mortality by 27%, ventricular arrhythmias by 65%, and angina symptoms by 40% in patients experiencing acute myocardial infarction1. These findings suggest that L-Carnitine could be a valuable adjunct therapy for improving cardiovascular outcomes.
Weight Management
L-Carnitine supplementation has been investigated for its potential benefits in weight management, particularly in overweight and obese individuals. A meta-analysis of randomized controlled trials found that L-Carnitine supplementation significantly decreased body weight, body mass index (BMI), and fat mass. However, it did not significantly affect body fat percentage or waist circumference. The anti-obesity effects were more pronounced when L-Carnitine was combined with other lifestyle modifications2.
Lipid Profile and Glycemic Control
L-Carnitine has been shown to improve lipid profiles and glycemic control in adults with cardiovascular risk factors. Meta-analyses have demonstrated that L-Carnitine supplementation significantly reduces total cholesterol, low-density lipoprotein cholesterol (LDL-C), and triglycerides while increasing high-density lipoprotein cholesterol (HDL-C). Additionally, L-Carnitine has been found to improve fasting plasma glucose, HbA1C, and insulin resistance (HOMA-IR)3 8.
Fatigue Management in Cancer Patients
Fatigue is a common symptom among cancer patients, and L-Carnitine has been explored as a potential treatment. However, a phase III randomized, double-blind, placebo-controlled trial found that L-Carnitine supplementation did not significantly improve fatigue levels in patients with invasive malignancies4. This suggests that while L-Carnitine may have other health benefits, its efficacy in managing cancer-related fatigue remains inconclusive.
Insulin Resistance
L-Carnitine has also been studied for its effects on insulin resistance. A meta-analysis of randomized controlled trials indicated that L-Carnitine supplementation significantly improved insulin resistance, as measured by the Homeostasis Model Assessment of Insulin Resistance (HOMA-IR). The benefits were more pronounced with prolonged supplementation5.
Exercise Performance
L-Carnitine has been shown to enhance exercise endurance capacity by promoting muscle oxidative metabolism. Studies in animal models have demonstrated that L-Carnitine administration increases fatty acid oxidation, reduces body fat, and enhances mitochondrial biogenesis in skeletal muscle. These effects contribute to improved endurance performance during prolonged exercise9.
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Adverse Effects of L-Carnitine
Liver Dysfunction and Inflammation
L-Carnitine supplementation can disturb hepatic fatty acid β-oxidation and lipid synthesis, leading to liver dysfunction and increased production of reactive oxygen species (ROS) and inflammatory cytokines1 3.
High L-Carnitine intake can induce liver injury, evidenced by increased serum AST and ALT activities and inflammatory liver cytokines3.
Kidney Function
Long-term L-Carnitine supplementation may disturb kidney function by altering renal protein levels and organic ion transporters1.
While some studies suggest that L-Carnitine up to 6000 mg/day is generally safe for healthy adults, the risks and benefits on kidney function in athletes and bodybuilders remain unclear4.
Intestinal and Digestive Issues
Common side effects of L-Carnitine include intestinal digestive problems2.
Circulatory System and Atherosclerosis
Oral L-Carnitine supplementation can increase levels of trimethylamine-N-oxide (TMAO), which is associated with atherosclerosis and circulatory system abnormalities5 9.
Mental Status
In some cases, L-Carnitine can affect the mental status of the user2.
Oxidative Stress and Apoptosis
Chronic L-Carnitine supplementation can increase tissue L-Carnitine concentrations and decrease oxidative stress and apoptotic markers in peripheral organs8.
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How has L-Carnitine Improved Patient Outcomes?
Improvement in Insulin Sensitivity and Glycemic Control
L-Carnitine supplementation improved insulin resistance in critically ill acute stroke patients, as evidenced by a significant decrease in HOMA-IR and insulin levels1 9.
Enhanced Quality of Life in Hemodialysis Patients
L-Carnitine supplementation improved general health, physical function, and vitality in hemodialysis patients, although the effects were not sustained over six months2.
Intravenous L-Carnitine reduced fatigue and may help preserve exercise capacity in hemodialysis patients3.
L-Carnitine reduced intra-dialytic hypotension and muscle cramps, and improved post-dialysis asthenia and maximal oxygen consumption7.
Reduction in Erythropoietin Requirements
L-Carnitine treatment led to a significant reduction in erythropoietin requirements in hemodialysis patients, suggesting improved anemia management6 8.
Improved Postoperative Outcomes in Liver Surgery
Perioperative L-Carnitine treatment in hepatectomized patients resulted in faster restoration of serum ammonia levels, prothrombin time, and neutrophil count, and reduced the incidence of posthepatic liver failure, leading to shorter hospital stays4.
Cardiac Function in Chronic Heart Failure
L-Carnitine supplementation improved clinical symptoms and cardiac functions, including left ventricular ejection fraction, stroke volume, and cardiac output, in chronic heart failure patients5.
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L-Carnitine Mechanisms of Action
Fatty Acid Transport and β-Oxidation
L-Carnitine facilitates the transport of long-chain fatty acids into the mitochondrial matrix, where they undergo β-oxidation to produce energy3 9.
Nutrigenomic Effects
L-Carnitine modulates the activity and expression of nuclear receptors (e.g., PPAR, RAR, RXR, VDR) in adipocytes, hepatocytes, and skeletal muscle cells, promoting lipolytic gene expression and reducing genes linked to adipogenesis and insulin resistance1.
Antioxidant and Anti-inflammatory Properties
L-Carnitine reduces oxidative stress and inflammatory responses by inhibiting TNF-α and IL-1β, and enhancing antioxidant enzyme activities (e.g., T-SOD, CAT, GSH-PX)2 7.
Cardioprotective Effects
L-Carnitine protects against cardiac damage by reducing oxidative stress, inflammatory cell infiltration, and improving tissue architecture in myocardial infarction models2 8.
Regulation of Glucose Metabolism
L-Carnitine improves insulin-mediated glucose disposal and regulates acetyl and acyl cellular trafficking, which is crucial for meeting energy demands and controlling glycolytic and gluconeogenic enzyme synthesis3.
Exercise Endurance
L-Carnitine enhances exercise endurance by promoting muscle oxidative metabolism, increasing fatty acid oxidation, and sparing muscle glycogen during prolonged exercise6.
Neurobiological Effects
Acetyl-L-carnitine (ALCAR) modulates brain energy metabolism, synaptic transmission, and neurotrophic factors, showing potential benefits in conditions like Alzheimer’s disease and depression10.
Protein and Lipid Metabolism
L-Carnitine upregulates genes involved in fat decomposition (e.g., cpt1) and protein synthesis (e.g., mtor), enhancing growth and reducing lipid accumulation in various models9.
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Common Complaints Associated with L-Carnitine Use
General Safety and Tolerability
L-Carnitine is generally well-tolerated with no significant side effects or toxicities noted at doses up to 3000 mg/day in patients with cancer-related fatigue1.
In athletes and bodybuilders, L-Carnitine up to 6000 mg/day is considered safe, with no significant adverse effects on kidney function reported4.
Potential Adverse Effects on Liver Function
High intake of L-Carnitine can impair liver function by altering gut bacteria composition, leading to increased liver enzymes (AST, ALT), inflammatory cytokines (IL-1, IL-6, TNF-α, TNF-β), and lipid metabolism disorders5.
Impact on Renal Function
There is no conclusive evidence of adverse effects on kidney function in healthy individuals, but the risks and benefits in athletes and bodybuilders have not been fully evaluated4.
Effectiveness and Side Effects in Hyperthyroidism
L-Carnitine is effective in reversing and preventing symptoms of hyperthyroidism without noted toxicity, teratogenicity, or contraindications3.
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Disclaimer
The content presented in this blog is generated by Consensus, an AI-powered academic search engine, and is based on publicly available scientific literature. While every effort is made to provide accurate, up-to-date, and well-researched information, the content is intended for informational and educational purposes only. It does not constitute medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional before making any decisions regarding medical conditions, treatments, or medications. The AI system’s analysis may not cover all perspectives, emerging research, or individual cases, and it is not a substitute for professional expertise. Neither the blog publisher nor the developers of the AI-powered search engine are responsible for any actions taken based on the information provided in this content. Use of this information is at your own risk. Citations to the original scientific studies are included for reference, but these studies should be reviewed in full and interpreted with the guidance of a healthcare or research professional.
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