Epimedium (horny goat weed)

What is epimedium?

Epimedium is a genus of flowering plants used in traditional Chinese medicine, where it is known as yin yang huo. In the West it is marketed as “horny goat weed,” a name drawn from a legend about goats becoming more sexually active after grazing on it. The leaves contain flavonoids, especially icariin, which is often used as a marker compound in extracts.

What the research says

Most research on epimedium is laboratory and animal work on icariin and its metabolites. A 2022 review explained that after oral intake, most icariin is converted by gut bacteria into icariside II. In laboratory and animal studies, icariin and its derivatives inhibited PDE5 (the enzyme targeted by drugs such as sildenafil), promoted testosterone synthesis and affected pathways involved in repairing erectile tissue (Niu et al., 2022). These are mechanistic findings; they do not show that an epimedium supplement improves erections in men.

We found no well-designed randomized trials of epimedium alone for erectile dysfunction, libido or prostate health. A broad meta-analysis of herbal supplements for erectile dysfunction did not identify epimedium monotherapy trials among its included studies, highlighting how thin the human evidence is (Borrelli et al., 2018).

Claims that epimedium supports “your health and your immune system” or the prostate are not based on clinical data.

How it’s used in supplements

Horny goat weed is a staple of male enhancement products, usually as a leaf extract standardized to a percentage of icariin. Many labels list the plant amount without the icariin content, so actual potency is unknown.

Short-term use is generally reported as well tolerated, but safety data in humans are limited. Higher doses have been associated with dizziness, dry mouth, nosebleeds and rapid heartbeat in reports. Because icariin may act on PDE5 and blood vessels, combining epimedium with erectile dysfunction drugs, nitrates or blood pressure medicines could add to their effects. It may also have blood-thinning and hormone-like effects. Avoid it in pregnancy, and talk to a doctor if you have heart disease, a bleeding disorder or a hormone-sensitive condition.

The bottom line: epimedium is popular because its main compound behaves like a weak version of erectile dysfunction drugs in the laboratory, but that has not been confirmed in good human trials, and product potency is rarely disclosed. Erectile problems can be an early warning sign of heart disease or diabetes, so they are worth discussing with a doctor rather than self-treating with herbal blends.