Taking L-carnitine supplements seems to improve sperm mobility in men with poorly active sperm, a problem known as asthenozoospermia, Italian researchers report in the medical journal Fertility & Sterility.
However, for L-carnitine to work, tiny structures within the cell called mitochondria must function properly. Mitochondria are important because they provide the energy needed for sperm to move their tail and swim.
Senior investigator Dr. Carlo Foresta said "it is well known that in some asthenozoospermic subjects an improvement of sperm (motion occurs) after carnitine administration. However in other asthenozoospermic patients this effect is not present."
To investigate further, Foresta of the University of Padua and colleagues studied 30 asthenozoospermic men divided into two groups depending on whether they had normal or abnormal mitochondria function. Patients took 2 g/day of L-carnitine for three months.
In patients with normal mitochondria function, movement rose from 29.3 percent before treatment to 41.1 percent after 3 months of l-carnitine. However, in those with abnormal function, movement held steady at about 24 percent.
Thus, Foresta concluded that carnitine treatment is useful "in ameliorating sperm motility only when optimal mitochondrial function is conserved."
Garolla, A, et al, Oral carnitine supplementation increases sperm motility in asthenozoospermic men with normal sperm phospholipid hydroperoxide glutathione peroxidase levels. Fertility and Sterility, 2005 Feb;83:355-361.