It is considered a "vitamin-like" and "amino-acid-like" compound that is related to the B vitamins. When it was first studied back in the s, L-carnitine was referred to as vitamin BT. L-carnitine is formed in the liver and kidneys from the amino acids lysine and methionine.
However, it is stored elsewhere in the body, primarily in muscle including the heart , the brain, and even in sperm. In the diet, it mainly comes from meat and other animal products. You can get some from plant products like avocado and soybeans, but as a rule, meat is the best source—and the redder the better. Carnitine exists in two forms: D-carnitine and L-carnitine. The L-form is the kind of carnitine found in nature and is biologically active. They're all similar, and similarly effective.
The D form of carnitine, on the other hand, is biologically inactive and isn't sold as a supplement. It can be found throughout the central nervous system, where it plays a role in producing energy and produces the important neurotransmitter acetylcholine. The acetyl group attached to the carnitine molecule enhances its ability to pass across the blood-brain barrier and enter the brain, where it acts as a powerful antioxidant.
For this reason, some research suggests that acetyl L-carnitine may provide protective actions against aging processes and neurodegeneration.
L-carnitine helps to transport fat, particularly long-chain fatty acids, into the mitochondria of cells. Once there, the fatty acids can be oxidized—used as fuel—to generate adenosine triphosphate, or ATP. L-carnitine does this cellular work both when you exercise and rest, but research confirms that it is especially effective during intense exercise. Without adequate carnitine, most dietary fats can't get into the mitochondria and be burned for fuel. But for people with carnitine deficiency, it is a serious medical condition.
It can lead to muscle weakness, stunted growth, an enlarged liver, and a number of other problems. This is one reason it's considered a "conditionally essential" nutrient: Your body produces it, but if it doesn't produce enough, your health can be seriously impacted. A study out of Scotland concluded that in addition to its fat-transporting work, L-carnitine also enhances insulin's actions on muscle cells.
This is one reason I advocate taking this supplement with a post-workout meal. Some of the most interesting research into L-carnitine supplementation focuses on how it can enhance athletic performance. L-carnitine's bona fide role as a fat-burning supplement is well established. Some people also have genetic conditions that make it difficult for them to produce L-Carnitine and can benefit from L-Carnitine supplementation.
L-Carnitine works by transporting fatty acids from food into the mitochondria of the cell. There, they are converted into energy. This allows you to burn fat during workouts, and at the same time, it will prevent muscle failure, fatigue, and that sluggish feeling many people experience, especially during a dieting phase. The energy that is produced from the fatty acids can be used by the heart, brain, and muscle, causing a positive effect on all three of these parts in the body. Besides fat loss, other benefits of L-Carnitine include increased endurance and enhanced muscle recovery.
Many athletes notice a significant boost in their performance when they supplement with L-Carnitine. They may also experience better muscle gains and have an easier time getting back into the gym after difficult workouts. L-Carnitine supplementation can also help with cognition and better brain function.
You may find that you have an easier time focusing when you take it on a regular basis, especially if your diet is lacking in L-Carnitine or the other amino acids that act as precursors to it. L-Carnitine supplementation may slow down the aging process due to its effect on cellular health as well. Also, L-Carnitine supplements are stimulant-free. They do not contain any caffeine or other stimulants that are found in other popular energy supplements and drinks.
This is important to note because you can take L-Carnitine any time of day. You can also add it to your current pre-workout supplement stack without worrying about being kept up all night. It is recommended that you take between g of L-carnitine per day, divided into two or three evenly split dosages. Many people find that they experience the best results when they take L-Carnitine with between 30 and 40 grams of carbohydrates.
This is because carbohydrates spike insulin levels. In order for the L-carnitine to enter the muscle cells and do its job, insulin levels need to be elevated. Taking L-Carnitine when insulin is elevated also helps to deliver more glucose to the muscle cells. This, in turn, helps to boost energy and workout performance. You can also stack L-Carnitine with caffeine-containing supplements as part of your pre-workout ritual.
Since it's stimulant-free, it pairs well with coffee, green tea, or your other favorite pre-workout supplement. Carnitine preparations administered orally can occasionally cause heart-burn or dyspepsia [ 86 ]. It is worthy to mention that Bakalov et al. The strength of this review is a focus on the period of LC treatment, very important aspect often missed in many articles dealing with this supplement.
This limitation is also magnified by the varied design of the studies available including different supplementation protocols and outcome measures. There is also a high degree of heterogeneity among participants of the analyzed studies. Therefore, the results should be taken with caution, and more research is required before definitive recommendations. Lasting for several years opinion that LC supplementation does not change metabolism, especially exercise metabolism, is based mostly on short-term supplementation protocols.
Nevertheless, LC is still used by elite [ 9 ] and sub-elite [ 10 ] athletes. Recent studies suggest that LC supplementation may elevate muscle TC content; therefore, modify muscle fuel metabolism and performance during the exercise. Due to insulin-mediated LC transport to the muscle, oral administration regimen should be combined with CHO. Because of LC poor bioavailability, it is likely that the supplementation protocol would take at least 3 months.
Shorter period of supplementation may be effective in prevention of exercise-induced muscle damage, but not metabolic changes. On the other hand, it is also clear that prolonged LC supplementation elevates fasting plasma TMAO [ 16 , 17 , 18 , 58 , 59 ], compound supposed to be pro-atherogenic [ 61 ]. Therefore, additional studies focusing on long-term supplementation and its longitudinal effect on the TMAO metabolism and cardiovascular system are needed.
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