Horny goat weed for men is thought to improve sexual function by increasing blood flow to the penis. Because it contains phytoestrogens (compounds that act like estrogen), horny goat weed has also been studied for osteoporosis (weak and brittle bones), a condition common in people undergoing menopause.
This article discusses the possible uses, side effects, precautions, and other safety concerns of horny goat weed. Ginsenoside
Supplement use should be individualized and vetted by a healthcare professional, such as a registered dietitian, pharmacist, or healthcare provider. No supplement is intended to treat, cure, or prevent disease.
Horny goat weed, also known as Epimedium, yin yang huo, or herbal “Viagra,” is a plant used in traditional Chinese medicine.
The main studies on horny goat weed were conducted in vitro (in test tubes) or in animal studies. Erectile dysfunction and bone disorders are the two most commonly studied conditions.
Other potential health benefits (limited to animal and/or test tube studies) of horny goat weed or its main components (natural chemical compound) include the following:
Human clinical studies are lacking, but preliminary evidence suggests icariin, a chemical compound in horny goat weed, inhibits a protein linked with erectile dysfunction called phosphodiesterase type 5 (PDE5).
Phosphodiesterase-5 inhibitors, such as horny goat weed and Viagra, widen the blood vessels, increasing blood flow to the penis needed for an erection. Erectile dysfunction occurs when there is not enough blood flowing to the penis.
A systematic review noted that horny goat weed was one of the most common ingredients in testosterone and erectile dysfunction supplements.
Further human studies are needed to determine the efficacy of horny goat weed for erectile dysfunction.
Some people believe that horny goat weed can also improve sexual function in women. The supplement is sometimes also used to treat health problems after menopause, such as high cholesterol and low estrogen.
Horny goat weed should not be used in people who are pregnant or breastfeeding.
There is limited evidence that horny goat weed may help reduce bone loss. A study in postmenopausal individuals showed horny goat weed extract increased the activity of bone-forming cells and decreased bone breakdown. The study was limited because it was unclear if changes in biomarkers would translate to clinical efficacy.
The bone-protective effect of icariin, the main active component in horny goat weed, is due to its estrogenic activity based on animal models.
Furthermore, another clinical trial showed icariin prevented bone loss compared to a placebo. Both groups were also given 300 milligrams (mg) of elemental calcium daily. Since the treatment group consisted of icariin and other sources of phytoestrogens, the effect of icariin alone on osteoporosis was unclear.
Horny goat weed may have side effects. These side effects may be common or severe.
A randomized, double-blind, placebo-controlled trial evaluating the safety of horny goat weed in 58 postmenopausal people reported no side effects during the eight-week observational period.
However, a review reported the following side effects:
One clinical trial evaluating the effect of horny goat weed on estrogen levels and fat metabolism in postmenopausal participants showed no significant side effects of horny goat weed.
Additionally, horny goat weed has not been linked with endometrial hyperplasia (irregular thickening of the uterine wall).
Stop taking horny goat weed if you have any signs of an allergic reaction.
If you're having a severe allergic reaction or if any of your symptoms feel life-threatening, call 911 and get medical help right away.
Certain people should not take horny goat weed including:
Use horny goat weed with caution if you take the following medications:
It is essential to carefully read a supplement's ingredient list and nutrition facts panel to know which ingredients and how much of each ingredient is included. Please review this supplement label with your healthcare provider to discuss potential interactions with foods, other supplements, and medications.
Always speak with a healthcare provider before taking a supplement to ensure that the supplement and dosage are appropriate for your needs.
Horny goat weed is available as a capsule, tablet, powder, or tea. While horny goat weed supplement is available as a single active ingredient, it can also be found in combination with other supplements purported to improve erectile dysfunction.
Although the standard dose of horny goat weed is unclear, the doses used in some clinical trials are noted below.
In one trial of people in postmenopause, two 370 milligram capsules of horny goat weed extract (48.2% prenylflavonoids and 6.9% icariin) daily for six weeks. In another trial, 60 milligrams of icariin, 15 milligrams of daidzein, 3 milligrams of genistein, and 300 milligrams of elemental calcium daily were used.
Horny goat weed extract containing phytoestrogens has been safely taken by adults by mouth for up to two years. Another extract containing icariin has been taken safely for up to six months.
Using certain types of horny goat weed for a prolonged period or at higher doses is possibly unsafe. Serious side effects, such as severe breathing problems, have been reported.
If you plan to take this supplement, look for a product with a seal of approval from a third-party organization that provides quality testing. These include U.S. Pharmacopeia, ConsumerLab.com, and NSF International.
Note that a seal of approval from one of these organizations does not guarantee that the product is safe or effective. But it does assure you that it was made correctly, contains the ingredients listed on the label, and does not contain harmful contaminants.
It is important to note that supplements with some of the most significant risks of contamination are the ones promising sexual enhancement.
A study in rats found a significant herb-drug interaction between horny goat weed extract and Viagra (sildenafil). Specifically, horny goat weed extract decreased the concentration of Viagra. This decreased how effective Viagra was. Since this was an animal study, it's unclear how the results may apply to humans. Further human clinical studies are warranted to clarify the interaction between horny goat weed extract and Viagra.
Horny goat weed is an herbal supplement that some people use as a "natural Viagra" to treat erectile dysfunction. Some studies suggest it has other positive effects, especially on bone health. However, more rigorous human clinical studies are needed to clarify the health benefits of horny goat weed.
Caution should be taken if you have certain medical conditions or take certain medications. Consult your healthcare provider to determine if a horny goat weed supplement is right for you.
Prescription drugs such as Viagra (sildenafil) and Cialis (tadalafil) are PDE5 inhibitors. However, they should not be used with nitrate-containing medications—like Nitrostat (nitroglycerin) and Monoket (isosorbide mononitrate)—due to the risk of fatal low blood pressure. Although horny goat weed contains icariin, a mild PDE5 inhibitor, it's unclear how horny goat weed interacts with nitrate-containing medications due to the lack of studies on such safety concerns. Considering horny goat weed interacts with blood pressure-lowering medications by causing blood pressure to drop too low, it is essential to consult your healthcare provider before starting a horny goat weed supplement.
Because horny goat weed might decrease the speed at which the body processes caffeine, it can increase the side effects of caffeine if taken with caffeine-containing herbs and supplements, such as black tea, green tea, coffee, guarana, and yerba mate. Use extra caution if you're sensitive to caffeine.
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By Trang Tran, PharmD Trang Tran, PharmD, is a pharmacist who is passionate about integrative health.
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