Optimizing your performance through nutrition and supplementation is how you set yourself apart from the competition. L-carnitine is a proven ergogenic aid and has an arsenal of evidence that shows it can promote fat loss, optimize workout recovery, and enhance endurance in athletes. We’re going to show you the facts and discuss what l-carnitine is, its benefits, side effects, and more.
What Is L-Carnitine
Often thought of as an amino acid, l-carnitine is actually a vitamin like, and amino-acid like compound that is formed from the amino acids lysine and methionine. Carnitine is related to the B-Vitamins and was referred to as vitamin BT when it was first discovered.
The main function of l-carnitine is the transport of long chain fatty acids, into the mitochondrial matrix for oxidation and conversion to energy. L-carnitine also plays an imperative role in the regulation of metabolic signaling pathways involved in muscle protein balance, proteolysis and muscle protein synthesis.
L-carnitine shuttles long-chain fatty acids inside the mitochondria by forming a long chain acetylcarnitine ester. The complex is then transported into the mitochondrial matrix by carnitine palmitoyltransferase I (CPT I) and carnitine palmitoyltransferase II (CPT II).
The fatty acids are then broken down through the process of β-oxidation to deliver the 2-carbon molecules to the Krebs cycle, leading to the generation of energy under the form of adenosine triphosphate (ATP). In addition, by binding an acetyl group, l-carnitine can maintain the levels of Acetyl-CoA and coenzyme A, playing its buffering role.
What Are The Benefits Of L-Carnitine
Research suggests that L-carnitine has several beneficial effects on physical performance, demonstrating an increase in maximal oxygen uptake, and higher power output. Studies have also shown that L-carnitine supplementation may improve exercise recovery, by alleviating muscle injury, and reducing markers of cellular damage. Studies in older adults have shown positive impacts on physical and mental fatigue and that L-carnitine can lead to an increase in muscle mass and decrease in body weight[1]
1. L-Carnitine May Improve Weight Loss
One of the most well-known benefits of carnitine is it’s demonstrated efficacy on weight loss. L-Carnitine assists in transporting and oxidizing long chain fatty acids for muscle fuel or energy. Studies show that increasing total carnitine content could alter muscle fuel metabolism in two different ways during training. In addition to fat oxidation, L-carnitine also enhances insulin response, balancing glycogen levels by reducing carbohydrate use, consistent with an increase in body fat utilization.
A systematic review that investigated the beneficial effects of L-Carnitine supplementation for weight management in overweight and obese adults found that L-Carnitine significantly reduced weight, BMI, and fat mass[2]
2. L-Carnitine May Improve Workout Recovery
Workout recovery is crucial to overall athletic performance. Severe soreness can lead to potential injury due to overuse and increased muscular pain, interfering with your training schedule. If you can optimize recovery through nutrition and supplement protocols, you can effectively increase training volume and performance.
Research shows that l-carnitine has several different mechanisms which can reduce muscle soreness and post workout muscular pain. The association between L-carnitine and the regulation of metabolic pathways involved in muscle protein balance may help protect muscles against atrophy or muscle mass breakdown, which can reduce soreness.
Evidence suggests that l-carnitine supplementation attenuates the use of amino acids as an energy source, making them more bioavailable for protein synthesis. If there are more amino acids freely available, they can further assist in muscle growth and muscle repair[3]
Studies also suggest that l-carnitine may improve blood flow therefore reducing muscle catabolism, and markers of metabolic stress.[4]
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3. L-Carnitine May Enhance Endurance Capacity
Studies have shown that L-Carnitine can enhance endurance capacity, by improving oxygen uptake and reducing the build up of lactic acid. Increased endurance capacity directly translates to better sprint performance, time trials, and time to exhaustion.
A study published in the Journal Strength and Conditioning, investigated the effects of L-carnitine supplementation on endurance performance in athletes. 26 professional soccer players were divided into two groups and administered either 3g, or 4g of l-carnitine. Athletes participated in an exercise test, measuring time to exhaustion, with increased running speeds by 1KM every 3 minutes, until failure. The results showed that running speeds correlated to l-carnitine concentration, with an increase in running speed and decrease in heart rate. Thus, supplementing with l-carnitine pre workout, may benefit endurance and time to exhaustion.[5]
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Studies also show that L-Carnitine benefits high-intensity training by maintaining the acetyl CoA/CoA ratio constant, thereby allowing continuous flux through the pyruvate dehydrogenase complex and preventing lactate or lactic acid accumulation. Less lactic acid means more workout volume, and work capacity.
L-Carnitine Side Effects
If taken as prescribed at 500mg – 3g per day, l-carnitine supplements are generally considered safe. Minimal side effects have been reported, and may include nausea, abdominal cramps, and diarrhea[6]
L-carnitine may increase the effects of blood thinners like Coumadin (warfarin) and Sintrom (acenocoumarol), causing excessive bruising or bleeding. It can also decrease the effectiveness of thyroid medications.
If you are taking any other medications, we recommend consulting your physician to discuss any potential side effects, or interactions.
L-Carnitine Dosage
Most studies utilize l-carnitine in doses between 500-3g per day. Supplementing a minimum of 1g per day, is recommended to illicit any potential ergogenic benefit.
What Is L-Carnitine: Takeaway
Most of us that hit the gym five days a week, have the same goals. Those goals usually include getting fit, adding more muscle, losing body fat, and getting stronger. Research suggests that l-carnitine illicit positive effects when used as an ergogenic aid on athletic performance, endurance, recovery and body optimization.
Studies suggest that l-carnitine can increase muscle mass and decrease body weight, through fat oxidation and using muscle fat for fuel. Not only that, carnitine can balance glucose levels, and shift energy metabolism. L-carnitine has also been found to increase endurance, and workout volume by delaying muscle fatigue, increasing oxygen uptake, and reducing lactic acid buildup. Moreover, carnitine can improve blood flow and plays a pivotal role in muscle protein balance, reducing post workout muscle soreness.
Yet, despite the numerous clinical studies showing positive on weight loss and sports performance, there is also an equal number of studies, showing inconclusive or contradictory results. More clinical research is needed to confirm study results and provide conclusive evidence, of l-carnitines effectiveness as an ergogenic and weight loss aid.
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[1] Fielding, Roger et al. “l-Carnitine Supplementation in Recovery after Exercise.” Nutrients vol. 10,3 349. 13 Mar. 2018, doi:10.3390/nu10030349
[2] Moein Askarpour, Amir Hadi, Maryam Miraghajani, Michael E. Symonds, Ali Sheikhi, Ehsan Ghaedi, Beneficial effects of l-carnitine supplementation for weight management in overweight and obese adults: An updated systematic review and dose-response meta-analysis of randomized controlled trials Pharmacological Research, Volume 151,2020, 104554, ISSN 1043-6618, https://doi.org/10.1016/j.phrs.2019.104554.
[3] Owen KQ, Jit H, Maxwell CV, Nelssen JL, Goodband RD, Tokach MD, Tremblay GC, Koo SI. Dietary L-carnitine suppresses mitochondrial branched-chain keto acid dehydrogenase activity and enhances protein accretion and carcass characteristics of swine. J Anim Sci. 2001 Dec;79(12):3104-12. doi: 10.2527/2001.79123104x. PMID: 11811466.
[4] Huang A, Owen K. Role of supplementary L-carnitine in exercise and exercise recovery. Med Sport Sci. 2012;59:135-142. doi: 10.1159/000341934. Epub 2012 Oct 15. PMID: 23075564.
[5] Orer GE, Guzel NA. The effects of acute L-carnitine supplementation on endurance performance of athletes. J Strength Cond Res. 2014 Feb;28(2):514-9. doi: 10.1519/JSC.0b013e3182a76790. PMID: 24263659.
[6] U.S. Library of Medicine. ToxNet - L-Carnitine. Updated August 26, 2008.
