Ginseng has long been used in traditional Chinese medicine to boost immunity and lower blood sugar, but recent research suggests a new reason to consume the plant: to perk up, quite literally, a man's sex life.
In a study published last month in the International Journal of Impotence Research, scientists from the Yonsei University College of Medicine in Seoul, South Korea, found that men who suffered from erectile dysfunction and took tablets of ginseng berry extract daily for eight weeks saw improved sexual function.
The research team concluded that ginseng should be considered as an alternative medicine to improve all domains of sexual dysfunction.
A wealth of studies provide evidence that more than half of the world's male population has some degree of erectile dysfunction. Two main symptoms of sexual dysfunction are erectile dysfunction and premature ejaculation. Erectile dysfunction occurs when a man is not able to achieve or keep an erection for sexual intercourse.
Prevalence of erectile dysfunction in the Hong Kong population has been reported by University of Hong Kong's Urology Division as 61 per cent of men aged 51 to 60, 47 per cent of men aged 41 to 50, and 38 per cent of men aged 31 to 40.
To treat erectile dysfunction, drugs such as Viagra and selective serotonin reuptake inhibitors are commonly used.
However, these drugs may produce negative side effects such as headaches, gastrointestinal disorders or muscle pain, and are often contraindicated with other drugs and illnesses.
Furthermore, these drugs are not well tolerated by the larger proportion of men who are most likely to suffer from the condition - those living with heart disease, stroke, hypotension, hypertension or diabetes.
Researchers working on the Yonsei University study hypothesised that ginseng berry extract could be as effective and safe as synthetic drugs, which work in much the same way.
The pharmacological properties of ginseng have been studied and used for more than 2,000 years. In traditional Chinese medicine, Asian ginseng, particularly Panax ginseng, is used to increase strength, increase blood volume, promote life and appetite, and it has been prescribed for weakness, deficient qi patterns, anaemia and impotence.
Each part of the ginseng plant has distinct properties and research has provided evidence to show that the berry contains a greater amount of a ginsenoside (the active compound in ginseng), which enhances nitric oxide - a chemical important for relaxing muscles and improving blood flow for sexual function.
In the Yonsei University study, 119 married men between the ages of 20 and 70 were administered either four 350mg tablets of ginseng berry extract or a placebo daily for eight weeks. Efficacy of the tablets was assessed by a questionnaire known as the International Index of Erectile Function, which consists of 15 questions related to erectile function and sexual satisfaction.
The ginseng group scored significantly better in premature ejaculation. Other areas tested included intercourse satisfaction and sexual desire, which improved only slightly.
One member of the study team, Chung Woo-sik, a professor of urology at Ewha Womans University in Seoul, acknowledges that the extract is less efficacious than typical erectile dysfunction drugs.
"The [gingseng] tablets we used are not a drug, but a kind of complementary medicine or dietary supplement," he says.
A scientific review of natural aphrodisiacs published in the journal Food Research International in 2011 found that ginseng, along with saffron and a chemical from the African yohimbe tree, were proven sexual performance boosters. The researchers from the University of Guelph in Canada examined hundreds of studies on commonly used aphrodisiacs to investigate claims of sexual enhancement, both psychological and physiological.
According to the Hong Kong Urology Clinic, the cause of erectile dysfunction includes poorly controlled diabetes, atherosclerosis and depression. Erectile dysfunction can also develop because of stress, anxiety or bad lifestyle choices such as smoking or a poor diet, which can lead to weight gain.
Certain surgical procedures or medical treatments, such as prostate surgery or radiation treatment for cancer, can also cause erectile dysfunction, as well as many drugs including hypertensive drugs, antidepressants, alcohol and tranquilisers.
There is some concern that the Yonsei University study, and others like it, suggest natural remedies might exacerbate sexual problems as patients shun more conventional medication.
Dr Yiu Ming-kwong, consultant and division chief of the University of Hong Kong's Urology Division, believes that most patients in Hong Kong who are diagnosed by registered doctors feel positive about taking prescription medication.
"Most of them expect drug treatment from their GP or urologist during the consultation."
Yiu also believes that many sufferers are never treated.
"The important point is that a lot of men suffering from erectile dysfunction are too embarrassed to reveal their problem to their doctor. Instead, they will purchase over-the-counter drugs of various kinds, including drugs or tablets which claim to have ginseng."
In October last year, researcher Mario Liong Chan-ching surveyed approximately 1,000 Hong Kong women and men aged 36 to 80 with stable partners to determine attitudes towards sex and erectile dysfunction prescription drugs.
Study results showed Hong Kong women had a lower level of support for erectile dysfunction drugs for their partners than their counterparts in Europe, North America and Australia.