Maca is an herb that grows in the Andes mountains and has been used in that region for many years for its aphrodisiac and/or fertility-enhancing properties. Scientists at the Faculty of Sciences and Philosophy at the Universidad Peruana Cayetano Heredia in Lima, Peru, decided to put maca to a modern-day test.

They designed a 12-week double blind placebo-controlled, randomized, parallel trial to compare treatment with two different doses of maca with a placebo. The researchers wanted to find out whether the herb’s apparent effect on sexual desire “was because of effect on mood or serum testosterone levels.” They recruited a group of men aged 21 to 56 years of age who received maca in one of two doses: 1,500 mg or 3,000 mg per day, or a placebo. The researchers measure for self-perception on sexual desire, score for Hamilton test for depression, and Hamilton test for anxiety at 4, 8 and 12 weeks of treatment.

The researchers found a significant improvement in sexual desire at the 8-week point and onward. However, they found no difference in serum testosterone and estradiol levels between those receiving maca and those receiving a placebo. Scores for depression and anxiety were also unchanged. Therefore, maca’s effect on sexual desire is not linked to alterations in mood or sex hormone levels. The researchers could only conclude that “treatment with maca improved sexual desire” – though they don’t yet know why!

Andrologia 2002 Dec;34(6):367-72