Dr. Bob Murray (Cofounder of the Gatorade Sports Science Institute) Explains The Importance Of Carnitine
Carnitine is a small molecule found in all cells, where it plays a variety of roles involving carbohydrate and fat metabolism, stabilization of mitochondrial function, and as an antioxidant (Traina 2016). Although carnitine is produced in brain, liver, kidney, and heart cells, 95% of the body’s carnitine is found in skeletal muscle to help support the high metabolic activity of muscle cells. Biosynthesis of carnitine by the body accounts for only about 25% of our daily carnitine needs; the rest must come from the diet (e.g., meat and dairy products) (Fielding et al. 2018).
The free carnitine content of skeletal muscle can be increased by carnitine supplementation. Increasing intracellular carnitine helps maintain the balance between fat and carbohydrate metabolism (Stephens et al. 2013), reduce lactate production (Orer and Guzel 2014), and spare muscle glycogen, a response that is associated with lower ratings of perceived exertion and improved exercise capacity (Wall et al. 2011).
Shen et al. (2020) hypothesized that carnitine supplementation can reduce the neuromuscular fatigue associated with strength training involving blood-flow-restriction techniques by allowing for more contractions to occur prior to fatigue. And Stephens (2018) speculated that the improvement in endurance performance associated with carnitine supplementation may occur not only because of carnitine’s role in transporting fatty acids into the mitochondria, but to the important role carnitine plays in buffering the acetyl Co-A groups that are rapidly produced during high-intensity exercise, effectively reducing the production of lactic acid.
A systematic review and meta-analysis (Yarizadh et al. 2020) reported that carnitine supplementation improves muscle soreness and markers of muscle damage (CK, LDH, and Mb) in resistance-trained and untrained subjects. In Enhanced Recovery™ , carnitine is part of a synergistic blend of ingredients associated with reduction in muscle damage and delayed-onset muscle soreness and the increase in muscle protein synthesis during recovery (the other ingredients being omega-3 fatty acids, whey proteins, and collagen peptides.)
There is no doubt that the scientific literature on the effects of carnitine supplementation on various measures of metabolic response, exercise performance, and recovery remain mixed; some studies report benefits, while others do not (Fielding et al. 2018). Many of the studies of carnitine supplementation were done in the 80s and 90s, so it is likely that future studies using modern techniques will refine our understanding of the performance and recovery benefits of carnitine, especially when carnitine is part of a synergistic package of nutrients.
Fielding R, Riede L, Lugo JP, Bellamine A. L-carnitine supplementation in recovery after exercise. Nutrients. 2018;10(3).
Orer GE, Guzel NA. The effects of acute L-carnitine supplementation on endurance performance of athletes. J Strength Cond Res. 2014;28(2):514-519.
Shen L, Li J, Chen Y, Lu Z, Lyu W. L-carnitine’s role in KAATSU training-induced neuromuscular fatigue. Biomed Pharmacother. 2020;125:1-8.
Stephens FB, Wall BT, Marimuthu K, et al. Skeletal muscle carnitine loading increases energy expenditure, modulates fuel metabolism gene networks and prevents body fat accumulation in humans. J Physol. 2013;591(18):4655-4666.
Stephens FB. Does skeletal muscle carnitine availability influence fuel selection during exercise? Proc Nutr Soc 2018;77(1):11-19.
Traina G. The neurobiology of acetyl-L-carnitine. Front Biosci (Landmark Ed). 2016;21:1314-1329.
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. 2011;589(Pt 4):963-973.
Yarizadh H, Shab-Bidar S, Zamani B, Vanani AN, Baharlooi H, Djafarian K. The effect of L-carnitine supplementation on exercise-induced muscle damage: a systematic review and meta-analysis of randomized clinical trials. J Am Coll Nutr. 2020:1-12.