What is Acetyl-L-carnitine? Acetyl-l-carnitine (ALC) is a metabolically active nutrient that has a wide spectrum of positive effects. It has similar metabolic effects to L-carnitine, but ALC passes more easily into the bloodstream than L-carnitine, and also crosses the blood brain barrier far more effectively than L-carnitine, where it has a number of positive effects on brain function. Both ALC and L-carnitine play an important role in the metabolism of food and are vital for the transport of long chain fatty acids into the mitochondria where they will be used for energy. Both are naturally occuring substances, found in small quantities in our diets - particularly in: milk, red meat, poultry and seafood. The human body is able to produce 20% of its L-carnitine needs from the essential amino acids methionine and lysine.
Who might benefit from Acetyl-L-carnitine supplements? Anyone who is on a low calorie, vegetarian, low meat diet, or who trains intensively and for prolonged periods of time is prone to deficiencies in carnitine. L-carnitine is important for endurance athletes as its main function is to transport fatty acids inside the mitochondria (energy powerhouses within muscle cells) where oxidation of the fatty acids occurs, to produce energy. However, ALC passes more easily into the blood stream, and passes more freely into the mitochondria, where it has a greater work rate than L-carnitine. Research has also shown ALC to be more effective than L-carnitine (Hiat, 2004). ALC/l-carnitine supplementation is also believed to increase the use of fat for energy and therefore may be beneficial to people looking to loose weight.
What does research say about Acetyl-L-carnitine supplementation? It is well known that consumption of L-Carnitine has a protective effect on a number of cardiac diseases (Loster et al., 1993). Supplementation of L-carnitine protects against a deficiency within the inner cells of blood vessels (Hulsmann and Duebaar, 1988; Hiatt, 2004). This leads to improved delivery of oxygen to the working muscles both during and after exercise (Kraemer and Volek, 2000). Carnitine increases blood flow by improving the efficiency of fatty acid oxidation within the artery wall. It is also known to detoxify ammonia, a by-product of protein metabolism, that has been associated with early fatigue (Kanter and Williams, 1995). The improved blood supply during exercise is likely to improve performance, whilst the improved blood supply post exercise is likely to speed up recovery.
Many elite athletes have traditionally used L-carnitine to aid tolerance of high training loads and to speed recovery (Neumann et al., 2000). Research suggests that taking 1g per day during intense training periods may help to prevent decreases in muscle carnitine levels (Giamberardino et al., 1996). Improved recovery following L-carnitine supplementation is also supported by Volek et al., 2002, who demonstrated reduced: markers of muscle damage, reduced tissue damage, reduced muscle soreness as well as reduced levels of free radical damage.
As well as producing all of the physiological benefits described above, ALC has some additional benefits that won’t occur with plain L-carnitine supplemetation. Bidzinska et al., 1993, demonstrated that ALC supplementation helps to prevent a drop in testosterone production following periods of physical or mental stress. Further studies (Krsmanovic et al., 1994) have also demonstrated that ALC supplementation promotes the growth and activity of cells in the brain responsible for producing hormones that activate testosterone production. ALC may therefore help athletes to cope more effectively with the high levels of physical and mental stress associated with large training volumes. ALC acts as a general brain energizer by helping to maintain a constant supply of energy needed for normal brain function (Kidd, 1998; Kidd, 1999)
Supplementation of 2g of L-Carnitine has been demonstrated to reduce levels of muscle damage (Jeff et al 2002; Kraemer et al., 2003). Both of these research teams suggested that Carnitine supplementation may be particularly effective at improving the rate of recovery. There appears to be very clear evidence that L-carnitine supplementation has beneficial effects on training, competition, and recovery from strenuous training (Karlic and Lohminger, 2004). In this way ALC helps athletes to tolerate greater training loads, and therefore gives athletes the potential to train at higher levels with a reduced risk of overtraining.
One particularly promising aspect of L-carnitine supplementation is that it may have a long term positive effect that lasts beyond the supplementation period. Research looking at the positive effects of L-carnitine supplementation on cardiac patients found that exercise performance was still improved 60 days after supplementation was stopped (Loster et al., 1999). Therefore, you may still get a positive benefit from L-carnitine even when you have stopped taking it.
ALC has also been shown to improve mental function, alertness, reduce depression, improve memory, and to reduce the age associated decline in brain function (Cipolli and Chiari, 1990; Tempesta et al., 1990; Liu et al., 2002; McDaniel et al., 2003), and is particularly effective when combined with alpha lipoic acid (Liu et al.,2003).
Is Acetyl-L-Carnitine effective? ALC appears to be highly effective at enhancing the rate of recovery from exercise, reducing muscle soreness, improving heart function, enhancing brain function, and speeding up the transport of fats into the mitochondria.
How should I take Acetyl-L-carnitine? The general recommendation for ALC/L-carnitine supplementation is 1-2g per day during periods of intensified training (Neumann et al., 2000). It is generally recommended that this is taken on an empty stomach in the morning or early afternoon – try not to take late in the evening as ALC may make you feel more alert and therefore make it harder to sleep. High doses should be avoided as the excess is likely to be excreted and therefore wasted. When training load is reduced, ALC/L-carnitine intake should be stopped. This is important as it helps to ensure that the body's own production of ALC/L-carnitine is not disrupted and remains active.
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