The Science: Some studies have implied that feeding maca to domestic cattle increases sperm production, but there is very little data about any sexual effect on humans. One very small randomized double-bind trial of men with erectile dysfunction found that men taking maca extract reported a small increase in their ability to get erections. But so did the control group. As with the fenugreek study, a similar study with a larger group of people is needed to see whether any differences between the controls and the maca-eaters are real.
Erectile dysfunction supplements and other natural remedies have long been used in Chinese, African and other cultures. But unlike prescription medications for erectile dysfunction, such as sildenafil (Viagra), vardenafil (Levitra, Staxyn), tadalafil (Cialis, Adcirca) and avanafil (Stendra), erectile dysfunction herbs and supplements haven't been well-studied or tested. Some can cause side effects or interact with other medications. And the amount of the active ingredient can vary greatly from product to product.