Men who take carnitine supplements may be able to improve the function of their sperm; specifically, sperm mobility in cases in which their sperm is poorly active. That's the finding by a group of Italian researchers in a study published this past February.1
This condition is known in medical terms as asthenozoospermia (as-THEN-oh-zoo-SPERM-ee-uh).2
"Carnitine supplementation has been seen to ameliorate sperm motility [movement ability] in some cases of idiopathic asthenozoospermia, an effect possibly related to the particularly high concentration in the seminal fluid," wrote Carlo Foresta, MD, in the department of Medical and Surgical Sciences at the University of Padova in Italy, and his fellow investigators.
Currently, there are ART procedures offered to men who have problems with their sperm. For men desiring children who have low or no sperm motility, IVF is the therapy that doctors often choose to help a couple conceive. In this way, motile sperm can be collected, concentrated, and then placed in direct contacted with the egg in a culture environment. In cases in which IVF is not the answer for motility problems, intracytoplasmic sperm injection (ICSI) may be the next option. This is a procedure in which a single sperm is collected from a semen sample and injected directly into the egg for fertilization.3
A Metabolic Booster
Carnitine is an amino acid derivative in the body. It is produced naturally in the liver and kidneys and is subsequently sent to other tissues, particularly those that use fatty acids as part of the body's metabolism. Tiny structures in cells known as mitochondria—cellular energy-producing structures—use carnitine as part of the process of metabolism.4 Thus, for carnitine to help sperm move better, it is essential that mitochondria in the sperm are functioning properly, Foresta and his colleagues noted. Deficiency of this nutrient may be the cause of asthenozoospermia in the absence of other potential causes, they wrote.
To confirm this, 30 men with idiopathic asthenozoospermia were recruited for the small study. (The term "idiopathic" is attached to diseases that have no known cause.) The group of 30 asthenozoospermic patients was compared with a group of 30 men with normal fertility. Unknown to any of the patients, they were given daily doses of placebo for 3 months during the study, followed with doses of carnitine for an additional three months. Each man provided semen samples, which were assessed at the start of the research, after 3 months of placebo doses, and after 3 months of carnitine supplementation.
The semen "of the asthenozoospermic patients, compared with those of fertile subjects, presented the typical pattern of asthenozoospermia: decreased progressive motility and a reduced percentage of normal sperm morphology [appearance]," the scientists wrote. "On the other hand, sperm concentration and viability were in the normal range."
A Sperm Jump-Start?
At the end of the study, Foresta's team learned that in those men who had received carnitine supplements, there was "a significant increase in sperm motility, which disappeared when supplementation was suspended."
While it's only theory, Foresta's group speculates that carnitine helps delay a pre-programmed cellular suicide in sperm known as apoptosis (ap-ahp-TOE-sis), which could explain why it helps improve sperm motility.
Exceptions Found
But the findings only apply to men with normal mitochondrial function in their sperm. When the patients were subdivided into groups with normal versus abnormal mitochondria, those with normal mitochondria increased their sperm motility using carnitine supplements from 29.3% to 41.1% after 3 months. Contrast that with movement that increased very subtlety, from 23.9% to just 24.8% in those with abnormal mitochondria, Foresta and his team reported.
"Apparently, carnitine cannot protect mitochondria when already damaged or weakened," they concluded.
1. Garolla A, Maiorino M, Roverato A, Roveri A, Ursini F, Foresta C. Oral carnitine supplementation increases sperm motility in asthenozoospermic men with normal sperm phospholipid hydroperoxide glutathione peroxidase levels. Fertil Steril 2005 Feb;83(2):355-61.
2. Atlanta Center for Reproductive Medicine. Assisted Reproductive Technologies (ART). Available at http://www.acrm.com/IVF/ART.htm. Accessed March 9, 2005.
3. Curi SM, Ariagno JI, Chenlo PH et al. Asthenozoospermia: analysis of a large population. Arch Androl 2003 Sep-Oct;49(5):343-9.
4. The Linus Pauling Institute. Oregon State University. L-Carnitine. Available at: http://lpi.oregonstate.edu/infocenter/othernuts/carnitine/. Accessed March 9, 2005.
John Martin is a long-time health journalist and an editor for Priority Healthcare. His credits include coverage of health news for the website of Fox Television's The Health Network, and articles for the New York Post and other consumer and trade publications.
