Bremer J. Carnitine--metabolism and functions. https://doi.org/101152/physrev19836341420 [Internet]. 1983 [cited 2022 Sep 12];63(4):1420–80. Available from: https://journals.physiology.org/doi/
10.1152/physrev.1983.63.4.1420
Acetyl-L-carnitine
Acetyl-L-carnitine (often shortened to ALCAR) is the acetylated form of L-carnitine, a compound synthesised naturally in humans via methylation of the essential amino acid lycine. As this process by itself produces insufficient amounts of l-carnitine, healthy levels can be reached through consumption of dairy products and red meat. Additional supplementation may increase availability of l-carnitine to optimal levels, particularly in vegetarians (2).
L-carnitine is a key player of mitochondrial energy production in both skeletal muscles and brain neurones (3), and may also have a direct effect on concentration of major neurotransmitters including acetylcholine, noradrenaline and serotonin (4,5). This explains the potential of ALCAR as a nootropic for focus, and as a strength-boosting supplement.
Focus
ALCAR may help improve concentration: In a randomised, double-blind, placebo-controlled double-crossover trial, significant improvement of attention deficit in boys was achieved following supplementation with ALCAR (6).
Strength
There is a growing body of evidence linking ALCAR to improved exercise performance: In a double-blind, randomised trial, supplementation led to significant increase in total carnitine muscle content, glycogen sparing and reduced anaerobic ATP production (7). As a more practical measure, bench and leg press lifting volumes in young men were significantly increased following supplementation (8), and another trial has outlined the role of ALCAR in muscle recovery (9).
Safety Evidence
There is a sound physiological basis supporting ALCAR supplementation, and the above studies suggest it plays a role in improving focus and physical strength. It is safe to use, as ingestion of up to 3000mg daily did not lead to noticeable side effects or toxicity (10).
Read More About the Science
1
2
Rebouche CJ. Carnitine function and requirements during the life cycle. FASEB J [Internet]. 1992 Dec 1 [cited 2022 Sep 12];6(15):3379–86. Available from: https://onlinelibrary.wiley.com/doi/
full/10.1096/fasebj.6.15.1464372
3
Stephens FB, Constantin-teodosiu D, Greenhaff PL. New insights concerning the role of carnitine in the regulation of fuel metabolism in skeletal muscle. J Physiol [Internet]. 2007 Jun 6 [cited 2022 Sep 12];581(Pt 2):431. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2075186/
4
Doležal V, Tuček S. Utilization of citrate, acetylcarnitine, acetate, pyruvate and glucose for the synthesis of acetylcholine in rat brain slices. J Neurochem [Internet]. 1981 [cited 2022 Sep 12];36(4):1323–30. Available from: https://pubmed.ncbi.nlm.nih.gov/6790669/
5
Smeland OB, Meisingset TW, Borges K, Sonnewald U. Chronic acetyl-L-carnitine alters brain energy metabolism and increases noradrenaline and serotonin content in healthy mice. Neurochem Int [Internet]. 2012 Jul [cited 2022 Sep 12];61(1):100–7. Available from: https://pubmed.ncbi.nlm.nih.gov/22549035/
6
Van Oudheusden LJ, Scholte HR. Efficacy of carnitine in the treatment of children with attention-deficit hyperactivity disorder. Prostaglandins Leukot Essent Fat Acids [Internet]. 2002 Jul 1 [cited 2022 Sep 12];67(1):33–8. Available from: http://www.plefa.com/article/S0952327802903789/fulltext
7
Wall BT, Stephens FB, Constantin-Teodosiu D, Marimuthu K, Macdonald IA, Greenhaff PL. Chronic oral ingestion of L-carnitine and carbohydrate increases muscle carnitine content and alters muscle fuel metabolism during exercise in humans. J Physiol [Internet]. 2011 Feb [cited 2022 Sep 12];589(Pt 4):963–73. Available from: https://pubmed.ncbi.nlm.nih.gov/21224234/
8
Koozehchian MS, Daneshfar A, Fallah E, Agha-Alinejad H, Samadi M, Kaviani M, et al. Effects of nine weeks L-Carnitine supplementation on exercise performance, anaerobic power, and exercise-induced oxidative stress in resistance-trained males. J Exerc Nutr Biochem [Internet]. 2018 Dec 31 [cited 2022 Sep 12];22(4):7–19. Available from: https://pubmed.ncbi.nlm.nih.gov/30661327/
9
Parandak K, Arazi H, Khoshkhahesh F, Nakhostin-Roohi B. The Effect of Two-Week L-Carnitine Supplementation on Exercise -Induced Oxidative Stress and Muscle Damage. Asian J Sports Med [Internet]. 2014 [cited 2022 Sep 12];5(2):123. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4374610/
10
Cruciani RA, Dvorkin E, Homel P, Malamud S, Culliney B, Lapin J, et al. Safety, tolerability and symptom outcomes associated with L-carnitine supplementation in patients with cancer, fatigue, and carnitine deficiency: a phase I/II study. J Pain Symptom Manage [Internet]. 2006 Dec [cited 2022 Sep 12];32(6):551–9. Available from: https://pubmed.ncbi.nlm.nih.gov/17157757/