Horny goat weed a flop
Horny goat weed won't make you horny, despite being an ingredient in many over-the-counter natural supplements that promise an improved libido.
Experts at Wake Forest Baptist Medical Centre in North Carolina, in the US, evaluated the most common ingredients in supplements sold to bolster male sexuality to see if they worked and were safe - and concluded that there was little evidence that they stimulated the libido .
Some natural supplements were found to be both ineffective and risky, with reported side-effects such as high blood pressure, headaches, seizures, constipation, rashes, insomnia and liver damage.
Horny goat weed, common in South African dietary supplements, was deemed safe but ineffective.
Ginkgo biloba, also found in many sex enhancement pills in South Africa, had "no convincing data to support its use in men with erectile dysfunction".
However, "it can cause headaches, seizures and significant bleeding, especially if patients are also taking [the blood thinner] warfarin," said the researchers.
They found that ginseng could cause headaches, upset stomach, constipation, rashes, insomnia and depressed blood sugar, a problem for diabetics.
"Herbal medicines are not tested for efficacy or safety," said South African sexologist Dr Eve.
"So, people should not be buying them - they are dangerous."
Another sexologist, Elmari Mulder Craig, said many patients used herbal supplements instead of consulting a doctor.
"Supplements work for only a week or two because of the placebo effect.
"Erectile dysfunction could be a warning that within three to five years you will have a heart attack. You must be seen by a doctor or neurologist if you have erectile dysfunction.
"Usually herbal supplements don't work. It's throwing money in the fire," said Mulder Craig.
The US study showed that 81% of "natural" sexual products contained PDE5Is, the active ingredient in Viagra.
Using these products without a doctor's examination is unsafe, especially for people with heart, liver or kidney problems .