Carnitine as a Supplement

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preferential fuel selection during exercises. And by suggesting that the availability of free carnitine in skeletal muscle could be altered in human subjects, there would be a possibility to eliminate carnitine as a limiting factor for fat oxidation. This could generate both scientific and commercial interest due to potential enhancement effect on sports performance.

Wächter S, Vogt M, Kreis R, Boesch C, Bigler P, Hoppeler H, Krähenbühl S. 2002. Long-term administration of l-carnitine to humans: effect on skeletal muscle carnitine content and physical performance. Clinica Chimica Acta. 318(1-2): 51-61. doi: 10.1016/S0009-8981(01)00804-X.

In this primary study, the effect of long-term L-carnitine supplementation of high dosage on the skeletal muscle composition and athletic performance was investigated in healthy man (Wächter et al. 2002). 2*2g of L-carnitine were given as daily supplement to eight male subjects for three months. Needle biopsy on muscles and physical performance on bicycle ergometer across 20~60% individual max work load (P max) were measured pre- and post-treatment, and following a two-month washout period. Researchers found no significant difference across physical performance indicators (e.g. VO2 max, P max) across all three time points of measurement. And the composition of skeletal muscles in terms of total carnitine content, mitochondrial enzymatic activities and muscle fiber composition were not influenced by long term L-carnitine supplementation. It was evident from this research paper that long-term oral administration of L-carnitine had no significant impact on healthy adult males with respect to physical performance. However, this study only involved a small number of male participants, and had no control group, which weakened the conclusions. It was not clear if a period of three months was sufficient to analyse long term effects of L-carnitine administration and whether this would contribute significantly to improvement in endurance sports performance.