l-Carnitine is a popular supplement amongst athletes in the belief that it will increase performance and recovery. This concept is largely based on the fact that carnitine assists in the transport of fat across cell membranes in muscle tissue and is involved in cellular energy production. Additionally, carnitine reduces insulin secretion and significantly improves peripheral glucose use, when administered with glucose, according to human research (Grandi et al 1997). There is evidence that l-carnitine supplementation may increase maximal oxygen consumption, stimulate lipid metabolism and reduce post-exercise plasma lactate (Karlic & Lohninger 2004).
In a placebo-controlled crossover trial using an l-carnitine-l-tartrate (LCLT) supplement (2 g l-carnitine/day) for 3 weeks, researchers suggested that LCLT supplementation was effective in assisting recovery from high-repetition squat exercise (Volek et al 2002). However, other clinical trials using 2 g l-carnitine twice daily for 3 months found no significant increase in muscle carnitine content, mitochondrial proliferation, or physical performance (Wachter et al 2002).
Trials in subjects with cardiovascular disorders have been more promising. This is supported by the clinical trial discussed earlier involving patients with chronic stable © 2007 Elsevier Australia
angina (Iyer 2000). In addition, a clinical trial using 1 g l-carnitine or placebo three times daily for 120 days has indicated a potential for improved performance and effort tolerance in patients with cardiac insufficiency (Loster et al 1999).
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