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The leaves of various species of epimedium have been used as the herb known as yin yang huo, which literally translates as horny goat weed, in traditional Chinese medicine. The various species grow naturally from southern central to northern coastal China as well as Korea. Other species of epimedium are found in many parts of the world, though their similarity to horny goat weed is uncertain.
For these conditions, treatment consists of tea made from 5 grams (1 tsp) simmered in 250 ml (1 pint) of water for 10 to 15 minutes, three times daily
How It Works
Horny goat weed contains a number of flavonoids, some of which show estrogen-inhibiting properties in the test tube. These hormonal actions may be part of the reason horny goat weed has been used traditionally to treat sexual disorders, and why it has shown efficacy in clinical trials in patients with kidney failure for improving sex drive. Other flavonoids in horny goat weed, such as icariin, appear to stimulate the cells that build bone (osteoblasts). Rats given flavonoid extracts of horny goat weed are protected against osteoporosis. A number of flavonoids showed effects on the immune system that are both stimulating and suppressing depending on the circumstances in the test tube. Preliminary human trials in people with kidney disease undergoing dialysis confirm that horny goat weed can improve the function of various portions of the immune system. Icariin protects liver cells in the test tube.
A water extract of horny goat weed has been shown to inhibit growth of new blood vessels, a property potentially useful in stopping the growth of cancerous tumors. Extracts of the herb were moderately effective at inhibiting growth of cancer cells in the test tube, though icariin by itself was not. Icariin was effective at causing some cancer cells to become more normal in the test tube.
Lignans have also been found in various species of horny goat weed. Some lignans have been shown in one animal study to stimulate nerve growth.
A combination of horny goat weed with three other herbs has been shown to inhibit inflammation in several animal studies. This might in part explain the observed utility in early studies on the use of horny goat weed–containing formulas in people with hay fever. The immune effects of the flavonoids might also be relevant here.
A water extract of the whole herb of horny goat weed was shown to strongly inhibit a herpes simplex virus in the test tube. Water extracts of horny goat weed have also been shown to reduce blood pressure in several animal species and to reduce cholesterol levels. These extracts have been reported to be helpful in combination with several other herbs in people with what is described in Chinese medicine as kidney yang deficiency, presenting as what would be called in the West hardening of the arteries to the brain leading to dementia. This formula was more effective than one not containing horny goat weed. The effectiveness was correlated with antioxidant, cholesterol-lowering, and anti-inflammatory effects seen in the people taking the horny goat weed–containing formula.
In traditional Chinese medicine, horny goat weed is usually combined with yin tonic herbs when used long term for support of sexual health. If this is not done, it is believed the herb could cause problems such as aggressiveness, irritability, fever, or other “hot” symptoms (such as racing heart beat). In animal studies, prolonged use of excessive amounts of horny goat weed was associated with decreased thyroid activity.
Interactions with Supplements, Foods, & Other Compounds
At the time of writing, there were no well-known interactions with this supplement.
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