Horny goat weed is an ornamental plant that also has a long history of traditional use in Asian herbal medicine. Its whimsical name is said to derive from folk observations that goats who grazed on the herb became unusually sexually active. Horny goat weed is said to “tonify the kidney yang”; this is an expression whose meaning cannot be fully explained without entering into the theoretical framework of Traditional Chinese Medicine, but in a loose sense it signifies warming and invigorating the core energy of the body. Traditional uses of the herb (generally in formulas involving several other herbs as well) include treatment of male sexual dysfunction, prostate and urinary problems, low back pain, knee pain, poor memory, emotional timidity, and general symptoms of aging. The above-ground portion of the plant is used medicinally.
Horny goat weed is currently marketed as a sexual stimulant for both men and women, and also as a treatment for menopausal symptoms. However, there is no meaningful scientific evidence to support these proposed uses. Statements on multiple websites claim that it increases testosterone levels, inhibits acetylcholinesterase (a chemical important in the function of the nervous system), and has been shown to act as an aphrodisiac in mice. However, the references cited on these sites do not support these statements. What limited scientific is available is at best is far too preliminary to prove anything at all.1-9
According to test-tube studies and preliminary human trials, a different species in the same family, Epimedium brevicornum, may have estrogenic activity.10-12,16 However, even if this were to apply to horny goat weed as well, it would not indicate effectiveness for menopausal symptoms. Many herbs with estrogenic effects in the test tube do not appear to help menopausal symptoms (Interestingly, the one herb that most reliably appears to affect menopausal symptoms, black cohosh, does not have estrogenic effects in the test tube.)
A study of yet another distinct species, Epimedium koreanum, seems to be the source of the widespread claim that horny goat weed affects acetylcholinesterase.13
In fact, only double-blind, placebo-controlled studies can begin to prove a treatment effective, and none have been performed on horny goat weed taken by itself. The only study of this type tested a combination of horny goat weed, maca, Lepidium meyenii, Mucuna pruriens, and Polypodium vulgare.14 It supposedly found benefit, but its design and reporting were markedly inadequate, and the results are unreliable.
A typical dose of horny goat weed is 250-1,000 mg daily.
The safety of horny goat weed is unknown. There is one case report in which use of a horny goat weed product caused rapid heart rate and manic-like mood changes in a 66-year-old man.15 It is not clear whether the herb itself caused the symptoms, as it is possible the product used by this individual might have been adulterated or contaminated with an unlisted active substance.
Safety in young children, pregnant or nursing women, or people with severe liver or kidney disease has definitely not been established.
1. Wang S, Zheng Z, Weng Y, et al. Angiogenesis and anti-angiogenesis activity of Chinese medicinal herbal extracts. Life Sci. 2004;74:2467-2478.
2. Chen KM, Ge BF, Ma HP, et al. The serum of rats administered flavonoid extract from Epimedium sagittatum but not the extract itself enhances the development of rat calvarial osteoblast-like cells in vitro. Pharmazie. 2004;59:61-64.
3. Lin CC, Ng LT, Hsu FF, et al. Cytotoxic effects of Coptis chinensis and Epimedium sagittatum extracts and their major constituents (berberine, coptisine and icariin) on hepatoma and leukaemia cell growth. Clin ExpPharmacol Physiol. 2004;31:65-69.
4. Wu H, Lien EJ, Lien LL, et al. Chemical and pharmacological investigations of Epimedium species: a survey. Prog Drug Res. 2003;60:1-57.
5. Liao HJ, Chen XM, Li WG, et al. Effect of Epimedium sagittatum on quality of life and cellular immunity in patients of hemodialysis maintenance [in Chinese]. Zhongguo Zhong Xi Yi Jie He Za Zhi. 1995;15:202-4.
6. Chen X, Zhou M, Wang J et al. Effect of Epimedium sagittatum on soluble IL-2 receptor and IL-6 levels in patients undergoing hemodialysis [in Chinese]. Zhonghua Nei Ke Za Zhi. 1995;34:102-104.
7. Kuang AK, Chen JL, Chen MD. Effects of yang-restoring herb medicines on the levels of plasma corticosterone, testosterone and triiodothyronine [in Chinese]. Zhong Xi Yi Jie He Za Zhi. 1989;9:737-738, 710.
8. Cheng QL, Chen XM, Shi SZ, et al. Effects of Epimedium sagittatum on immunopathology and extracellular matrices in rats with chronic renal insufficiency [in Chinese]. Zhonghua Nei Ke Za Zhi. 1994;33:83-86.
9. Liu F, Ding G, Li J, et al. Effects of Epimedium sagittatum Maxim. polysaccharides on DNA synthesis of bone marrow cells of "yang deficiency" animal model caused by hydroxyurea [in Chinese]. Zhongguo Zhong Yao Za Zhi. 1992;16:620-622, inside back cover.
10. Meng FH, Li YB, Xiong ZL, et al. Osteoblastic proliferative activity of Epimedium brevicornum Maxim. Phytomedicine. 2005;12:189-193.
11. Zhang CZ, Wang SX, Zhang Y, et al. In vitro estrogenic activities of Chinese medicinal plants traditionally used for the management of menopausal symptoms. J Ethnopharmacol. 2005;98:295-300.
12. Yap SP, Shen P, Butler MS, et al. New estrogenic prenylflavone from Epimedium brevicornum inhibits the growth of breast cancer cells. Planta Med. 2005;71:114-119.
13. Oh MH, Houghton PJ, Whang WK, et al. Screening of Korean herbal medicines used to improve cognitive function for anti-cholinesterase activity. Phytomedicine. 2004;11:544-548.
14. Lamm S, Couzens GS. Effect of horny goat weed herbal complex supplement on sexual satisfaction in healthy men and men treated with Viagra. The Hormone Shop website. Available at: http://www.thehormoneshop.com/hornygoatweed.htm#Effect. Accessed June 30, 2005.
15. Partin JF, Pushkin YP. Tachyarrhythmia and hypomania with horny goat weed. Psychosomatics. 2004;45:536-537.
16. Zhang G, Qin L, Shi Y. Epimedium-derived phytoestrogen flavonoids exert beneficial effect on preventing bone loss in late postmenopausal women: a 24-month randomized, double-blind and placebo-controlled trial. J Bone Miner Res. 2007 Apr 9 [Epub ahead of print].
Last reviewed December 2015 by EBSCO CAM Review Board Last Updated: 12/15/2015