Horny Goat Weed is an herbal extract used to enhance libido. The extract from the plant Epimedium owes its imaginative name to the story of an unknown Chinese shepherd. He reportedly observed increased sexual activity in his herd of goats after they had grazed on a pasture overgrown with the plant. Because the libido-enhancing properties are partly attributed to the testosterone-boosting effect of the plant extract, it is also promoted as a supplement to increase muscle strength and mass.
Table of Contents
In this review, I will use available scientific research on Horney Goat Weed to determine the validity of these claims. In part II, I will discuss the influence on the stress hormone cortisol and the female sex hormone estrogen, as well as any side effects.
“Geile geitenkruid”
Some supplements sell themselves with their name. The Chinese name for Epimedium, a genus that includes about 25 species of plants, is Yin(g) Yang Huo or Xian Ling Pi, which literally means “libidinous goat weed” but is more loosely translated as “horny goat weed.” According to tradition, Epimedium has been included in Chinese traditional medicine by Tao Hongjing, a physician and Taoist who lived around 500 A.D. He heard a shepherd speak of the increased “sexual potency and mating frequency” of goats after they had eaten a plant that resembled an apricot plant. He then conducted tests with this plant, and the results confirmed what the shepherd had said. In Chinese traditional medicine, it is believed that the kidneys have a function in sexual activity (“part of Ying”), so he suspected that this herb strengthened the function of the kidneys and thus libido.
Epimedium species are now found in more and more places, and new species are still being discovered, especially in Japan.
*In Western medicine, there is no connection between the kidneys and libido. However, the adrenal glands contribute to sexual activity by producing male and female sex hormones, although the amount is very low compared to the production by sex glands.
Plants contain multiple substances. If a particular effect is attributed to a plant, it is always necessary to search for the component of the plant responsible for this effect. Epimedium is believed to contain icariin, the active ingredient responsible for increased libido, although the influence of other components is also considered.
Icariin: A Weak Version of Viagra?
Various effects are attributed to icariin. One of them is that it would work as a so-called PDE5 inhibitor, thus improving the quality of an erection (erectile function). PDE5 inhibitors are now extremely popular and well-known worldwide. They have caused a true sexual revolution among people over 50 and party-goers, made the porn industry much easier for men, and extended activities at the Playboy Mansion by decades. I am of course talking about sildenafil, which you probably don’t recognize, but is the active ingredient of Viagra. Tadalafil, the active ingredient of Cialis, is also a PDE5 inhibitor.
Pharmaceutical company Pfizer has had problems with patent allocation for Viagra. This is because a PDE5 inhibitor as a helper for erectile dysfunction is not exactly new, as it has been described in Chinese traditional medicine. However, the Chinese did not know which component of the plant was responsible for this effect or how.
PDE5 stands for the enzyme phosphodiesterase type 5. This enzyme has a breaking influence on smooth muscle tissue in the walls of blood vessels, including the two erectile bodies of the penis. Here, PDE5 inhibitors work as local NO boosters by blocking the action of this enzyme. By increasing the amount of nitric oxide in the blood, vasodilation occurs, relaxing the smooth muscle tissue in the blood vessels of the erectile bodies and increasing blood flow, thereby strengthening the erection.
However, icariin and sildenafil are not comparable. The chemical structure differs fundamentally, but above all, the effectiveness differs. Sildenafil is 80 times more powerful than icariin (1). And this is already about the active ingredient purified from Horny Goat Weed, while when taking the extract, only a part consists of icariin.
In a 2006 study, the erectile bodies of rabbits were injected with a solution containing the herbal extract of Epimedium. The effects were compared to those of Viagra. Viagra was found to be ten times more potent, even though amounts of icariin were used that are normally not achievable in the bloodstream (2).
So, Horny Goat Weed does work as an aphrodisiac (named after the Greek goddess Aphrodite), but its effectiveness is considerably lower than modern medications such as Viagra and Cialis. If you have had some “issues down there,” they are likely not to be resolved with horny goat weed. However, if you are looking for a natural alternative and it is mainly about improving an already good libido, then Horny Goat Weed may be interesting.
Horny Goat Weed as a Testosterone Booster
Horny Goat Weed is also promoted as a testosterone booster. However, the results of various studies on this are not uniform. For example, five years ago, researchers looking at the relationship between icariin and testosterone saw a negative correlation (3). Below, you can see the effect on testosterone in rats as observed by them. The researchers severed the nerve control (which largely controls an erection) so that they could stimulate it themselves. One group of rats was left untouched as a control group (CONT), another group received the treatment but no icariin, to also take into account any effects of the intervention (SHAM). The remaining treated rats were divided into three groups receiving different doses, expressed in milligrams per kilogram of body weight.
Firstly, you can see that severing the nerve control to the penis did not leave without effect. In the Sham group (“sham” means “pretend/fake”), you can see that testosterone has also decreased. It is not very surprising that deliberately induced impotence affects masculinity. It is important to compare the potential influence of icariin both with this group and with the control group. After all, the control group shows the normal conditions in rats, but does not take into account the influence of the intervention, while the sham group, on the other hand, takes into account the influence of the intervention but does not consider that this intervention itself may also influence the effect of icariin.
Looking at the effect of icariin at different doses, we see that the best result is obtained at the lowest concentration. This is only good compared to the Sham animals. Compared to the control group, it is a small decrease. Larger doses show a significant decrease compared to both the control group and the sham group. One mg/kilogram of body weight would amount to 80mg per day for someone weighing 80 kilograms, while 10mg would amount to 800mg per day. However, Horny Goat Weed is sold in much larger doses of 500mg to 1000mg per capsule. Daily recommended doses range from 1000mg to 2000mg. If 800mg per day in rats results in testosterone levels three times smaller, what effect will 2000mg have?
The strange thing is that in another study where icariin was orally administered to rats, much larger doses of 200mg per kilogram of body weight tripled testosterone compared to the control group (4). This would amount to 16000mg, or 16 grams, for someone weighing 80kg, which is 8 to 16 times the often recommended daily dosage. The answer may lie in the nature of the rats used. For this study, the rats were injected with a substance that inhibits testosterone production in the testes. This would make the rats more similar to older men with reduced testosterone production.
Nevertheless, these results are quite spectacular. The tripling of testosterone comes from rats treated with the enzyme that lowered their testosterone and later received icariin (M) compared to “normal” rats (C). So, one may wonder what the increase would have looked like if the rats had not first received the enzyme that lowered testosterone. Possibly, the increase would have been even higher. “T” was the group that received testosterone directly instead of ICA, which is why this level rose so quickly.
The problem with this study is that very large doses are used, and one may wonder what the side effects are (part II).
Personal Experience
Horny Goat Weed is offered by many different suppliers. From Bodyenfitshop, I received the Horny Goat Weed from their own label. The capsules contain 750mg of Horny Goat Weed and are quite large. I have also seen other products with 1000mg per capsule. Unless they compact the herb more per capsule, that seems like a rather high dosage. Although regular supplement users are often experienced pill swallowers, some may still have difficulty with the size.
I have tried it for a week now with 2 capsules per day on rest days and an extra capsule on training days before the workout. In the first few days, I noticed a “spontaneous slight increase in sexual tension at unexpected moments.” Extra energy, as some users have reported on the Bodyenfitshop site, I have not yet experienced myself. However, I will continue to use the horny goat weed for a few more weeks (at least until the pot is empty) and mention any other experiences here.
At a price of €9.90 for 90 capsules of 750mg, the Horny Goat Weed from Bodyenfitshop is very competitively priced when you realize that some providers offer half this quantity for double the price. Unfortunately, you cannot see how much icariin is in the herb. Some suppliers, such as Now Foods, standardize the percentage of icariin (at least 3%) so that you know how much you are getting.
Conclusion
There is still much more research to be done on the effect of icariin on erectile function and testosterone, preferably in healthy men. There may be significant differences with rats whose nerve control to the penis is interrupted and rats with deliberately reduced testosterone production. Regarding a natural alternative to Viagra, (the active ingredient of) Horny Goat Weed seems rightly a candidate, although its effect is much smaller, and possibly large amounts of the herbal extract are needed. When it comes to the influence on testosterone, it is unclear what the dosage-dependent effect is and whether high doses have a positive or negative effect.
References
- Dell’Agli M, Galli GV, Dal Cero E, Belluti F, Matera R, Zironi E, Pagliuca G, Bosisio E. Potent inhibition of human phosphodiesterase-5 by icariin derivatives. J Nat Prod. 2008 Sep;71(9):1513-7. doi: 10.1021/np800049y. Epub 2008 Sep 9.
- Chiu JH, Chen KK, Chien TM, Chiou WF, Chen CC, Wang JY, Lui WY, Wu CW. Epimedium brevicornum Maxim extract relaxes rabbit corpus cavernosum through multitargets on nitric oxide/cyclic guanosine monophosphate signaling pathway. Int J Impot Res. 2006 Jul-Aug;18(4):335-42. Epub 2006 Jan 5.
- Alan W. Shindel, MD,* Zhong-Chen Xin, MD,† Guiting Lin, MD, PhD,* Thomas M. Fandel, MD,*Yun-Ching Huang, MD,* Lia Banie, BS,* Benjamin N. Breyer, MD,* Maurice M. Garcia, MD,*Ching-Shwun Lin, PhD,* and Tom F. Lue, MD* Erectogenic and Neurotrophic Effects of Icariin, a Purified Extract of Horny Goat Weed (Epimedium spp.) In Vitro and In Vivo. J Sex Med. 2010 April; 7(4 Pt 1): 1518–1528.
- Zhang ZB, Yang QT. The testosterone mimetic properties of icariin.Asian J Androl. 2006 Sep;8(5):601-5. Epub 2006 Jun 5.
