Maca (Lepidium meyenii) is a root vegetable traditionally used in the Andes for enhancing fertility and sexual function. While its historical use is well documented, there has also been some scientific investigation into its effects on the male reproductive system. Several small randomized controlled trials and animal studies have suggested that maca supplementation may have a positive effect on sexual desire (libido) in men. For example, a 2002 study published in Andrologia found increased sexual desire in men after 8 and 12 weeks of maca supplementation compared to placebo. Some studies have also explored its effects on semen quality, with mixed results; a systematic review published in BMC Complementary and Alternative Medicine in 2010 concluded that while there is some evidence for improvement in semen quality, the number and quality of studies are limited.

It is important to note that while maca appears to have some influence on sexual function, the evidence for its impact on hormone levels (such as testosterone) is lacking or inconsistent. The overall scientific evidence for maca's support of the male reproductive system is therefore limited and preliminary, warranting a moderate evidence rating. Larger, well-designed clinical trials are needed to confirm these effects and clarify the mechanisms involved.