Carnitine as a Supplement

Carnitine, is a water soluble quaternary amine (3-hydroxy-4-N, N, N-trimethylaminobutyric acid) that has a vital role in metabolism, and is especially important in skeletal muscle tissues for good athletic performance. Being part of the metabolic pathway of the β oxidation of fatty acids, it is essential to have the carnitine shuttle for translocation of long chain fatty acids across the mitochondrial membrane. With higher level of muscle carnitine content, there would be elevated glycogen storage and better utilisation of fatty acids as muscle fuels, which could in turn enhance physical performance in sports.

Colombani P, Wenk C, Kunz I, Krähenbühl S, Kuhnt M, Arnold M, Frey-Rindova P, Frey W, Langhans W. 1996. Effects of L-carnitine supplementation on physical performance and energy metabolism of endurance-trained athletes: a double-blind crossover field study. Eur J Appl Physiol Occup Physiol. 73(5): 434-439. doi: 10.1007/BF00334420

This primary research aimed to study the relationship between short term intake of L-carnitine and the performance of endurance athletes (Colombani et al. 1996). Seven male marathon runners were recruited to this double-blind crossover study, and they were supplemented with 2g of L-carnitine prior to and during the marathon. Plasma concentration of metabolites and hormones, as well as respiratory exchange ratio (R) were measured at multiple time points. Moreover, the subjects were asked to complete a submaximal performance test to aid the research analysis. Study results only showed association between acute L-carnitine supplementation and plasma concentration of carnitine metabolites. There were no significant difference in any other outcome measurements e.g. marathon performance & recovery, R and plasma concentrations non-carnitine metabolites or hormones. It was concluded that short term L-carnitine administration had no significant impact on metabolism or sports performance for endurance athletes. This research study provided evidence to assess the effectiveness of carnitine as an acute supplement in endurance performance, however the results were of limited generalizability. The inclusion of more female endurance athletes as study subjects, and evaluation across a broader range of dosage would strengthen the conclusions from this research, and make them more generalizable.

Stephens FB, Constantin-Teodosiu D, Greenhaff PL. 2007. New insights concerning the role of carnitine in the regulation of fuel metabolism in skeletal muscle. J. Physiol. 581(2): 431-444. doi: 10.1113/jphysiol.2006.125799.

This review article summarised across many primary research papers that investigated the role of carnitine in skeletal muscle and the relationship between carnitine supplementation and athletic performance (Stephens et al. 2007). The researchers described the underlying mechanism of how carnitine is involved in the metabolic pathway, and showed its importance in regulating