L-Carnitine and Acetyl-L-Carnitine Improve Sperm Motility in Infertile Male Patients

L-carnitine and acetyl-L-carnitine are necessary for mitochondrial beta-oxidation of long-chain fatty acids, providing for their central role in cellular energy production. The highest levels of L-carnitine in the human body are found in the epididymal fluid, reaching 2,000 times the level in circulating blood. To initiate sperm motility the epididymal epithelium secretes L- carnitine into the epididymal lumen.

The importance of L-carnitine for sperm motility has led to the proposal that supplemental L-carnitine may be beneficial in the treatment of infertility caused by poor sperm motility. A six-month, double-blind, randomized placebo-controlled trial of combined L-carnitine (1,000 mg daily) and acetyl-L-carnitine (2,000 mg daily) was conducted on a group of 60 infertile males patients. Microscopic sperm analysis, seminal carnitine concentration, and sperm lipid peroxidation were evaluated at several designated times throughout the study. The treatment group demonstrated improved total and forward sperm motility (considered a measure of efficacy) compared to placebo. The most significant improvement was seen in patients who had lower initial absolute values of motile sperm. In addition, four pregnancies occurred in the treatment group. Subjects undergoing carnitine therapy showed no improvement in semen volume, sperm concentration, or percentage of sperm with normal morphology.

Lenzi A, Sgro P, Salacone P, et al. A placebo-controlled double-blind randomized trial of the use of combined l-carnitine and l-acetyl-carnitine treatment in men with asthenozoospermia. Fertil Steril 2004;81:1578-1584.

Additional Resources:
Male Infertility: Nutritional and Environmental Considerations (PDF)
Acetyl-L-Carnitine: Metabolism and Applications in Clinical Practice (PDF)
L-Carnitine: Therapeutic Applications of a Conditionally-Essential Amino Acid. (PDF)
Acetyl-L-Carnitine Monograph (PDF)