BACKGROUND:Cordyceps is an ancient Chinese herbal remedy made from the fungus Cordyceps sinensis. This is sometimes called the caterpillar fungus because it feeds on caterpillars and in its later phases can resemble a caterpillar. Cordyceps has been used for centuries in China as a general tonic. However, it is very expensive because it grows only at very high altitudes in the Himalayas of Tibet and China. Cordyceps grown in the wild is available, but its harvesting is controversial. Devout Buddhists living in the areas where it grows view the fungus as sacred, and oppose harvesting it for profit.
Global interest in cordyceps developed in the early 1990s, when relatively unknown female Chinese runners and swimmers broke several world records and won world championships. Accusations were made that they were using performance-enhancing drugs. However, the athletes and their coaches denied using any banned substance and said their improvements were due to rigorous training and a special diet that included cordyceps.
In response to the developing demand for cordyceps, a patented extract called Cs-4 was developed using fermentation technology. This allowed a cordyceps extract to be mass produced and made available as a food supplement. Cordyceps has become a popular supplement used to improve exercise performance, especially by older adults wishing to exercise for general health. It is reportedly taken by millions of older people in China.
EVIDENCE FROM STUDIES
Chemical analyses of cordyceps extract found that it contains a large variety of vitamins, minerals, amino acids, sugars and other compounds. Many of these act as antioxidants. Some studies with animals found that their exercise endurance was improved when they were fed cordyceps.
Controlled studies with humans have started to appear in just the past couple of years. Three randomised controlled trials have been conducted in highly trained cyclists.
None of these found any beneficial effects on various measures of endurance. Another study of healthy young men found no benefits in a jumping test after they took a supplement containing cordyceps as well as other herbs and minerals.
In spite of the widespread use of cordyceps by older Chinese people, the first controlled study involving older people was published in 2010. Healthy adults of over 50 were randomly assigned to take either placebo or cordyceps (using the fermentation extract Cs-4).
After three months, no differences were found between the groups in their performance on an exercise bicycle.
An earlier pilot study involving older adults had found improvements in an exercise bicycle test among those who took cordyceps, but not in those who took a placebo.
However, the two groups were not compared directly, and the full details of the study have not been published.
PROBLEMATIC ASPECTS
Cordyceps appears to be safe and well tolerated. Animals have been fed very large doses without adverse effects and have been given cordyceps for many months without problems. Some participants in clinical trials reported mild stomach discomfort, nausea and dry mouth.
RECOMMENDATIONS
The reputation gained by cordyceps from its use by Chinese athletes and older adults has not been supported by the results of clinical trials. Some claim this is because the type of cordyceps gathered in the wild is more beneficial than that grown for food supplements. Given that wild cordyceps is so expensive, affordable supplements will most likely continue to be made from the fermentation extract Cs-4. The studies conducted to date have found that this cordyceps extract does not improve exercise performance for either trained younger athletes or for older adults.
Dónal OMathúna has a PhD in pharmacy, researching herbal remedies, and an MA in bioethics, and is a senior lecturer in the School of Nursing, Dublin City University
