L-carnitine

Carnitine is required for the transport of fatty acids from the intermembraneous space in the mitochondria, into the mitochondrial matrix during the breakdown of lipids (fats) for the generation of metabolic energy.

Research
CFS patients have been found to have statistically significantly lower serum total carnitine, free carnitine and acylcarnitine levels. These serum levels were also found to correlate with clinical symptomatology. Higher serum carnitine levels correlated with better functional capacity. These findings may be indicative of mitochondrial dysfunction.

In a study in 1997 both L-carnitine and Amantadine were tested on 30 CFS patients. Amandatine was not well tolerated but the L-carnitine was found to be very safe and to improve the clinical status of CFS patients. Sarah Myhill checks Acetyl-L-carnitine levels as part of her Mitochondrial Function tests. 

The finding of CFS patients having lower carnitine levels was not reproduced in a study in 2000. They conclude based on 25 patients and 25 control that "there is no The present study demonstrates that serum carnitine deficiency does not contribute to or causes the symptoms in many CFS patients". . While this study indicates that not all CFS patients have these low levels it seems strong to claim there is no link at all.

In 2004 acetyl-L-carnitine, propionyl-L-carnitine, and its combination were compared in 3 groups of 30 CFS patients during 24 weeks. Acetylcarnitine significantly improved mental fatigue and propionylcarnitine improved general fatigue.