L-Carnitine
Status
FDA-approved. FDA-approved labeling exists for levocarnitine as Carnitor for primary and secondary carnitine deficiency, including in end-stage renal disease on dialysis. There is no approved indication for weight loss, athletic performance or body composition. Oral supplements are dietary supplements and are not reviewed for efficacy.
What it is
An amino acid derivative injected or taken orally for fat transport.
What published research measured
A quaternary amine required to transport long-chain fatty acids into mitochondria for oxidation, which is the entire theoretical basis for its use as a fat-loss agent. The human evidence does not follow the theory: meta-analyses of randomized trials find small effects on body weight at best, and muscle carnitine content is difficult to raise by oral supplementation because uptake is insulin-dependent and saturable. Better-supported uses are narrower — primary and secondary carnitine deficiency, where it holds approval, and haemodialysis-associated deficiency. A separate line of research complicates routine supplementation: gut bacteria metabolize carnitine to trimethylamine, which the liver converts to TMAO, a metabolite associated in observational studies with cardiovascular risk. Injectable preparations are compounded in most physique contexts.
Source
FDA labeling for Carnitor · TMAO and cardiovascular risk observational literature
Sources
No linked primary source is on file for this entry yet.
Educational use only, never medical advice. No doses.