Health Concern

L-carnitine is one of the most talked about substance for “fat burning” because it is commonly found in many weight loss supplements. L-carnitine is also used as an ergogenic aid among athletes to optimise endurance performance and muscle recovery. Is L-carnitine effective in weight management and endurance performance?

Let’s find out. 

 

⁠What is L-carnitine and where can we find them?

L-carnitine is a compound that exists naturally in all mammalian species. The name “carnitine” comes from the Latin word “carnis”, which means meat. Over 90% of L-carnitine is stored in the heart and skeletal muscle, whereas lower concentrations are found in plasma, liver, and kidney. Our body produces L-carnitine from two essential amino acids, lysine and methionine in the brain, liver, and kidney. Its synthesis requires nutrients like vitamin B6, niacin, vitamin C, and iron as cofactors. 

We can get L-carnitine from dietary sources, primarily animal-based foods, such as red meat, poultry, fish, and dairy products. Approximately 75% of the body’s carnitine pool comes from dietary sources while 25% comes from endogenous synthesis. A deficiency of L-carnitine is rare, even in vegans. 

 

How does L-carnitine support high performance?

L-carnitine is required for fat metabolism, energy production, as well as other bodily functions. In high performance athletes, L-carnitine is key for energy production during prolonged, intense training and competition. Let’s check out how L-carnitine works to enhance sports performance:

• Increasing fatty acid oxidation

L-carnitine plays a critical role as a “fat transporter” by facilitating the transportation of long-chain fatty acids (LCFA) from the bloodstream into mitochondria. LCFA undergo oxidation in the mitochondria to produce energy. The oxidation of fatty acids allows the body to utilise fat as a major source of fuel to ensure a sufficient energy supply during prolonged endurance exercise. This further reduces the body’s reliance on glycogen stores. 

• Sparing muscle glycogen

Glycogen is a stored-form of glucose in the liver and skeletal muscles. For endurance athletes like marathon runners, swimmers, and cyclists, muscle glycogen supply is key to supply the required energy for optimal performance. However, our bodies have limited glycogen storage. L-carnitine helps reduce the body’s reliance on glycogen stores by promoting fatty acid oxidation for use as fuel. This is important for delaying muscle glycogen depletion and fatigue, promoting an optimal muscle endurance capacity.  

• Buffer 

L-carnitine plays its buffering role to reduce the body’s reliance on carbohydrate breakdown for energy by promoting fatty acid oxidation. This helps minimise the accumulation of lactate, a byproduct of carbohydrate breakdown in the body. As a result, it further delays the onset of fatigue in the body, improving performance during high-intensity, prolonged exercise. 

• Antioxidant 

L-carnitine functions as an antioxidant to scavenge free radicals and minimises oxidative stress caused during intense exercise. This can alleviate inflammation caused by muscle damage and reduce the risk of muscle injury. This also helps in muscle recovery during resistance exercise or heavy training loads.

 

How and should athletes use L-carnitine?

While prioritising the “food-first” approach, athletes may need to consume L-carnitine supplements to have ergogenic effects for endurance performance in their high-intensity training and competition. The Australian Institute of Sport (AIS) recommends athletes consume 1.4 – 3 g of L-carnitine taken as a split dose with carbohydrate-containing meals for 12 weeks or longer. This is to facilitate the uptake of supplemental L-carnitine into muscle. 

However, the scientific evidence to support these claims is mixed. The hype surrounding its weight loss and performance-enhancing benefits may also be exaggerated. Athletes should consider getting advice from healthcare professionals prior to consuming supplements that contain L-carnitine. 

Summary

L-carnitine may offer potential benefits for weight management and endurance performance. As a “fat transporter”, L-carnitine is essential for fat metabolism. For endurance athletes, L-carnitine spares muscle glycogen, buffers lactate accumulation, and acts as an antioxidant for muscle recovery. While it shows beneficial effects in weight loss and endurance performance, the evidence is still mixed. Supplementation requires careful consideration and may be beneficial for some athletes under professional guidance.

 

Reference

Australian Institute of Sport. (2023). The Australian Institute of Sport (AIS) Supplement Framework. 

Caballero-García, A., Noriega-González, D. C., Roche, E., Drobnic, F., & Córdova, A. (2023). Effects of L-Carnitine Intake on Exercise-Induced Muscle Damage and Oxidative Stress: A Narrative Scoping Review. Nutrients, 15(11), 2587.

Fielding, R., Riede, L., Lugo, J. P., & Bellamine, A. (2018). L-carnitine supplementation in recovery after exercise. Nutrients, 10(3), 349.

Savic, D., Hodson, L., Neubauer, S., & Pavlides, M. (2020). The importance of the fatty acid transporter L-carnitine in non-alcoholic fatty liver disease (NAFLD). Nutrients, 12(8), 2178.