Acetyl-L-Carnitine (or ALCAR) is a naturally occurring molecule synthesised from L-Carnitine inside mitochondria by carnitine O-acetyltransferase enzyme . Acetyl-L-carnitine is a form of carnitine with acetyl group attached and is available as a supplement. In the terms of bioavailability acetyl-l-carnitine is claimed to be superior to L-Carnitine . Both are sold as a dietary supplement and are often promoted as an aid for weight loss, to improve exercise performance, and to enhance a sense of well-being .
Bioavailability – Acetyl-l-carnitine vs L-carnitine
Researchers prefer to use acetyl-L-carnitine in research studies because of its better absorption from the small intestine than L-carnitine. It also more efficiently crosses the blood-brain barrier (i.e., gets into brain tissue) . According to Charles J. Rebouche, bioavailability of oral l-carnitine supplementation (0.5-6 grams) ranges from 14%-18% of the total dose . Bioavailability of the acetylated form of L-carnitine (Acetyl-L-Carnitine) is thought to be higher than L-carnitine, however, not much is known regarding its metabolism. In humans, circulating acetyl-l-carnitine concentration was increased by 43% after oral acetyl-l-carnitine supplements of 2 g/day .
Aging and disease prevention
Carnitine is thought to contribute to the aging process because its concentration in tissues declines with age and thereby reduces the integrity of the mitochondrial membrane . Acetyl-L-carnitine supplementation may be beneficial in preventing age-related declines in energy metabolism, decreased oxidative stress, and improved memory, studies conducted on rats report [7,8]. ALCAR supplementation in rats has also been shown to reversed the age-related declines in tissue L-carnitine levels .
Acetyl-L-Carnitine has been shown to increase cognition in patients suffering from dementia of Alzheimer’s disease .
How much L-carnitine should you take?
After reviewing the studies on the function of carnitine Food and Nutrition Board (FNB) of the National Academy of Sciences concluded that carnitine is not an essential nutrient . Therefore, healthy children and adults do not need to supplement with it, as liver and kidney produce sufficient amounts (from the amino acids lysine and methionine). The FNB has not established recommended dietary allowance (RDA)—for carnitine .
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