What is L-Carnitine?
Carnitine, derived from an amino acid, is found in nearly all cells of the body. Its name is derived from the Latin carnus or flesh, as the compound was isolated from meat. Carnitine is the generic term for a number of compounds that include L-carnitine, acetyl-L-carnitine, and propionyl-L-carnitine.
Carnitine plays a critical role in energy production. It transports long-chain fatty acids into the mitochondria so they can be oxidized (“burned”) to produce energy. It also transports the toxic compounds generated out of this cellular organelle to prevent their accumulation. Given these key functions, carnitine is concentrated in tissues like skeletal and cardiac muscle that utilize fatty acids as a dietary fuel.
The body makes sufficient carnitine to meet the needs of most people. For genetic or medical reasons, some individuals (such as preterm infants), cannot make enough, so for them carnitine is a conditionally essential nutrient.
Benefits of L-Carnitine Supplementation
“A study examined the effect of acute L-carnitine loading on the endurance performance of footballers. The results show that 3 or 4 g of L-carnitine taken before physical exercise prolonged exhaustion.”
Measurements were performed on 26 candidate professional footballers who volunteered to take part in the study. Athletes were given a glass of fruit juice 1 hour before applying L-carnitine with the double-blind method. Then, 12 participants were given 3 g of L-carnitine (LK-3) and the remaining 14 were given 4 g (LK-4). Athletes began the exercise test at a running speed of 8 km·h and then continued at 10 km·h. The speed was increased 1 km·h every 3 minutes, and the test continued until the subject chose to quit. Heart rate was registered using a portable telemetric heart rate monitor during the test. Blood samples were taken from the earlobes of the footballers both before the test and before the speed increase (during the 1-minute interval), and the lactate (La) concentration was measured electroenzymatically. The test was repeated after 1 week as a group of placebos (P-3 and P-4). The result showed that the running speeds corresponding to specific La concentrations were increased, and La and heart rate responses to the running speeds were decreased in both supplemented groups compared with placebos (p ≤ 0.05). A significant reduction in heart rate was found in LK-4 and P-4 (p ≤ 0.05). When the Borg responses to the running speeds were analyzed, a significant difference was found in both supplemented groups (p ≤ 0.05).
“L-carnitine constant infusion improves insulin sensitivity in insulin resistant diabetic patients; a significant effect on whole body insulin-mediated glucose uptake is also observed in normal subjects.”
“Studies in athletes have shown that carnitine supplementation may foster exercise performance. As reported in the majority of studies, an increase in maximal oxygen consumption and a lowering of the respiratory quotient indicate that dietary carnitine has the potential to stimulate lipid metabolism.”
At doses of approximately 3 g/day, carnitine supplements can cause nausea, vomiting, abdominal cramps, diarrhea, and a “fishy” body odor [1-2]. Rarer side effects include muscle weakness in uremic patients and seizures in those with seizure disorders.
Some research indicates that intestinal bacteria metabolize carnitine to form a substance called TMAO that might increase the risk of cardiovascular disease . This effect appears to be more pronounced in people who consume meat than in vegans or vegetarians. The implications of these findings are not well understood and require more research.
Carnitine(β-hydroxy-γ-N-trimethylaminobutyric acid,3-hydroxy-4-N,N,N- trimethylaminobutyrate) is a quaternary ammonium compound involved in metabolism in most mammals, plants and some bacteria. Carnitine may exist in two isomers, labeled D-Carnitine and L-Carnitine, as they are optically active. At room temperature, pure carnitine is a white power, and a water soluble zwitterion with low toxicity. Carnitine only exists in animals as the L enantiomer, and DL-Carnitine is toxic as it is inactive but inhibits the activity of L-Carnitine. Carnitine, discovered in 1905 with a high density in muscle tissue was labeled Vitamin BT, however as carnitine is synthesized in the human body, it is not a vitamin. Carnitine is involved in the oxidation of fatty acids, and involved in systemic primary carnitine deficiency. It has been researched for preventing and treating other conditions, and may be used as an athletic performance enhancer.