Does Horny Goat Weed Really Work?

Horny Goat Weed is one of those herbs whose name evokes lingering curiosity – does it deserve its reputation in the bedroom? When I thought I’d found one lurking in my rockery, I discovered that there is a basis for its renowned use as an aphrodisiac, and that Horny Goat Weed is also undergoing research for benefits in other health conditions, including premenstrual syndrome (PMS), female menopause, male menopause, atherosclerosis (hardening and furring up of the arteries), osteoporosis, Alzheimer’s and even drug-resistant cancer.

Horny goat weed for men

In traditional Chinese medicine, Horny Goat Weed (Epimedium grandiflorum and Epimedium sagittatum) has been used for over 2000 years to enhance reproductive health in men. According to legend, it gained its reputation when a Chinese goat herder noticed increased sexual activity among his herd whenever they ate the plant which grew wild in his fields. Despite their bitter taste, he tried them himself and soon started recommending Horny goat weed to all his friends.

Horny goat weed is widely included in remedies to treat low sex drive, low fertility, impotence, pre-menstrual syndrome (PMS) and menopause. Horny Goat Weed is also used as a general tonic to maintain long-term, youthful vigour and good health.

Any herbal remedy that is consistently used for thousands of years is likely to have more than a placebo action. Pinning this down in the scientific literature isn’t easy, however, as leaves from 15 or more different species of Epimedium are used in traditional Chinese medicine. These are collectively known as Herba Epimedii, or Yin Yang Huo – a name that apparently translates as ‘obscene goat leaves of pulse plants’.

Horny goat weed is found in 11 of the top 30 supplements marketted for male sexual health. In the past, some supplements that included Horny goat weed also contained undeclared amounts of the male impotence drug, sildenafil (Viagra), so it’s important to buy a reputable supplement.

How does horny goat weed work

Each Epimedium species of horny goat weed contains its own unique blend of over 260 chemicals – including at least 37 different bioflavonoids. Of the ingredients that they all have in common, attention has turned to one called icariin, and its derivatives such as icaritin and a series of icarisides.

Early studies suggested that icariin found in Horny Goat Weed has a similar effect to l-arginine, Ginkgo biloba and drugs such as sildenafil (Viagra) which are prescribed to treat erectile dysfunction. These work by inhibiting an enzyme, phosphodiesterase type-5 (PDE5) which promotes blood vessel dilation during sexual stimulation to achieve and maintain an erection. Even dilute extracts from Horny Goat Weed contain enough icariin to inhibit the PDE5 enzyme by as much as 80%.

But Viagra isn’t an aphrodisiac – it requires sexual stimulation to work. So the ability of Horny Goat Weed to inhibit PDE5 would not produce an aphrodisiac effect, on its own. This action, while beneficial for goats with erection difficulties, is unlikely to account for apocryphal tales of goats (and men) becoming lusty soon after eating Horny Goat Weed leaves. Some other components with hormonal actions must be involved. The most likely candidates are bioflavonoids with an hormone-like action. A series of unique molecules (epimedins, epimedosides and icariososides) were recently extracted from the leaves of Epimedium (horny goat weed) and identified for the first time. So, after two millenia of traditional use, the evidence base for Horny Goat Weed’s aphrodisiac action is finally gaining some support.

Does horny goat weed make you horny?

Anecdotal evidence says yes, but there is currently no evidence-based explanation for exactly how Horny Goat Weed works as an aphrodisiac. Its action in treating erectile problems is on a firmer footing, however. Veterinary studies suggest it is effective in stimulating erections in aged, diabetic and even castrated animals. Perhaps surprisingly, its effects on human male and female sexual function have not yet been evaluated in gold-standard randomised, controlled trials.

How long does horny goat weed take to work?

Some people notice an effect within thirty minutes of taking it. Others find the effects slowly build up over a few weeks of use. Many supplements combine Horny Goat Weed with other prosexual supplements such as Maca Root, Tribulus Terrestris, Muira Puama, Panax Ginseng or L-arginine.

Horny goat weed for women

As well as containing unique oestrogenic flavonoids, Horny Goat Weed contains the isoflavones, genistein and daidzein, which are also found in soy. These isoflavones provide a useful oestrogen boost for older women, to reduce hot flushes, and to provide some protection against heart disease and bone loss.

Many women are unable or unwilling to take prescribed hormone replacement therapy to alleviate menopausal symptoms. A randomised controlled trial compared the effects of Horny Goat Weed against placebo in 90 post-menopausal women.

After six months, those taking Herba Epimedii showed significant improvements in total cholesterol and triglyceride levels, and increased blood levels of oestradiol, but no changes in progesterone or testosterone levels.

The researchers concluded that Horny Goat Weed has beneficial actions in postmenopausal women and added that, as no serious side effects were observed, the extract may be superior to HRT.

Unfortunately, there is no record of whether the women taking the Horny Goat Weed extract were asked if it affected their libido.

Horny goat weed and osteoporosis

Horny Goat Weed, or Herba Epimedii, is a traditional Chinese herbal medicine used to prevent and treat thinning bones.

One of the few human clinical trials to involve Horny Goat Weed tested extracts against placebo in a hundred postmenopausal women whose bone health was monitored for two years.

The women were randomised into two groups, with half taking an Epimedium extract (containing 60 mg Icariin, 15 mg Daidzein and 3 mg Genistein) plus 300mg calcium per day, while the other half took calcium alone.

After 24 months, significant differences were found between the two groups. In those taking low-dose calcium alone, bone mineral density decreased in the femoral neck by 1.8% and in the lumbar spine by 2.4%. In those also taking the Horny Goat Weed, however, bone mineral density increased at the femoral neck by 1.6%, and in the lumbar spine by 1.3%. Blood levels of chemicals associated with bone metabolism suggested that the extracts inhibited bone resorption and rebalanced bone turnover to favour new bone formation.

No changes were seen in blood levels of estradiol (a human oestrogen) nor endometrial thickness, and the researchers concluded that Epimedium-derived phytoestrogen flavonoids exert a beneficial effect on preventing bone loss in late postmenopausal women without detectable adverse effects.

Again, there is no record of whether the women taking the Horny Goat Weed extract in this study noticed any effects on their libido (I emailed the researchers to ask but had no response). Women may also find Rhodiola or St John’s Wort helpful for boosting a low sex drive.

Horny goat weed and Alzheimer’s dementia

Icariin from Horny goat weed may protect against dementia of Alzheimer’s type by inhibiting the build up of abnormal amyloid proteins, blocking the phosphorylation of tau protein, regulating calcium movements and reducing inflammation.

Horny goat weed and cancer

In laboratory studies, Horny goat weed icariin has anti-cancer activity against a wide range of human cancer cells, including those derived from stem cells and those which are drug resistant.

Icariin appears to work as a biological response modifier by triggering mechanisms that usually cause abnormal cells to self-destruct (apoptosis), by priming immune defences, by regulating the cell growth cycle, by preventing the ability of tumours to produce their own blood vessels, and by preventing cancer cell spread. Research also suggests that icaritin may be effective against hormone-dependent cancers (eg prostate, breast) that are resistant to hormone treatments, through effects on their hormone receptors.

It’s early days, and has not yet reached the stage of clinical trials, but icariin is under investigation as a potential anti-cancer drug to enhance the effectiveness of chemotherapy regimens.

Horny goat weed dose

The doses of horny goat weed contained in male sexual health supplements range from 50mg to 600mg.

Horny goat weed side effects

Horny goat weed appears to be well tolerated, and serious side effects are rare. There is one report of an elderly man with heart disease who developed a rapid heart rate and aggressive behaviour after taking it for two weeks, but it is not certain that Horny Goat Weed was the cause.

Could horny goat weed help you?

Horny Goat Weed has survived over 2000 years of use by discerning punters and may well have beneficial effects on libido and erectile function. These haven’t been scientifically quantified but there is a definite spike in interest in both Horny Goat Weed extracts, and in synthetic icariin derivatives – one of which was 80 times more potent in its ability to inhibit the PDE5 enzyme than icariin itself.