L-carnitine

L-carnitine is a naturally occurring amino acid derivative that plays a crucial role in sperm production and function.

1. Improves sperm motility: Two randomized controlled trials have demonstrated that men taking L-carnitine supplements had significant improvement in total number of moving sperm compared to placebo, especially in men with a baseline low percentage of motile sperm^1,2. Most importantly, the percentage of forward moving sperm was increased. This is important for sperm to be able to travel forward towards the egg for fertilization.
2. Increases sperm count: Research found a 50% improvement in sperm concentration in men taking L-carnitine supplements after 3 months and more than doubled in men after 6 months².
3. Improves sperm morphology (shape): Men taking L-carnitine supplements have a lower percentage of atypical sperm (i.e. improved sperm shape) compared to men taking placebo².
4. Antioxidant activity: L-carnitine has antioxidant properties, which may help protect sperm from oxidative damage; thereby, improving sperm quality and DNA integrity. A randomized controlled trial identified increased free radical scavenging capacity in men taking L-carnitine².

References:

1. Lenzi, A., Lombardo, F., Sgrò, P., Salacone, P., Caponecchia, L., Dondero, F., & Gandini, L. (2003). Use of carnitine therapy in selected cases of male factor infertility: a double-blind crossover trial. Fertility and sterility, 79(2), 292–300. https://doi.org/10.1016/s0015-0282(02)04679-4
2. Balercia G, Regoli F, Armeni T, Koverech A, Mantero F, Boscaro M. Placebo-controlled double-blind randomized trial on the use of L-carnitine, L-acetylcarnitine, or combined L-carnitine and L-acetylcarnitine in men with idiopathic asthenozoospermia. Fertil Steril. 2005;84(3):662-671. doi:10.1016/j.fertnstert.2005.03.064