Is horny goat weed extract really a sexual stimulant?

Horny goat weed extract is often sold as a male sexual stimulant in gas station restrooms. The little foil packages claim to enhance male performance in exchange for three quarters inserted simultaneously into a wall-mounted vending machine.

What exactly is horny goat weed extract, and is there scientific possibility that it improves sexual performance?

Is horny goat weed extract really a sexual stimulant?S

What is horny goat weed?
Horny goat weed extract is a natural product of the plants in the Epimedium genus, with a history of use in Eastern medicine to relieve fatigue and weakness in the back and knees. The Epimedium genus contains a number of leafy green plants primarily used for groundcover. Within the sixty plus plants in the genus, Epimedium grandiflorum and Epimedium sagittatum are the two members most commonly associated with horny goat weed.

The raw leaves can be chewed or eaten, but the plant is typically sold as an extraction in powder or in pill form. Since horny goat weed extract's status is a natural product containing a variety of molecules, the substance cannot be patented. One molecule, however, is the decidedly active ingredient in the mixture.

Is horny goat weed extract really a sexual stimulant?S

How does the extract act on the body?
Icariin is the main active molecule in horny goat weed extract. Icariin inhibits the activity of the protein phosphodiesterase type 5 — this initially sounds insignificant, but the action plays a major role in increasing male sexual stimulation.

PDE5 is a protein lying in the smooth muscle cells of the penis, waiting to break down cyclic GMP. When the action of PDE5 is inhibited, erections become more likely. This is the same biological process used by the pharmaceutical sildenafil, better known as Viagra, to attain erections. Sildenafil, however, is more potent when it comes to inhibiting the action of PDE5.

Icariin also increases the amount of nitric oxide produced in cells that line the interior of blood vessels. The presence of nitric oxide in the blood vessels decreases the resistance blood meets as the fluid moves through the circulatory system, making erections easier to obtain.

Icariin, the active ingredient in horny goat weed extract, can aid in producing erections in the same manner as a prescription pharmaceutical. But how much icariin is in your dose horny goat weed extract?

Is horny goat weed extract really a sexual stimulant?S

What's in your horny goat weed?
Retail horny goat weed extracts contain 5 to 60% icariin, with the number varying due to standardization procedures used in processing. You are likely to receive a lot less icariin in the foil packages sitting in the gas station lavatory.

Dosage becomes a major problem with horny goat weed extract. The mixture is not regulated by the Food and Drug Administration, so data on the amount necessary to obtain the desired effect is elusive. Users report better experiences after several days of taking the supplement. Icariin does not bind to PDE5 as tightly as sildenafil, leading icariin to fail in producing the almost immediate response observed with Viagra.

Horny goat weed extract has a number of other traditional uses that often manifest as side effects from long-term consumption as a sexual stimulant. A precipitous decrease in blood pressure is common in long-term users (which, logically, makes sense due to icariin's stimulation of nitric oxide production), as well as cardiovascular problems. If you're looking for a long-term (and quick acting) sexual aid, check out one of the many prescription pharmaceuticals, like Viagra and Cialis, made available in the past decade and a half.

Images by cote/flickr, wallygrom/flickr, and jeremyfoo/flickr.