An American species commonly used in alternative medicine is Panax quinquefolium. Chinese ginseng has been used as a medical treatment for over 2,000 years to improve mental alertness and increase energy. Chinese ginseng contains a number of compounds which are thought to act together to produce its beneficial effects. Ginsenosides, of which more than a dozen have been identified, are believed to increase energy, relieve stress, and enhance physical and intellectual performance. Other compounds include the panaxans, which may lower blood sugar, and polysaccharides, which may enhance the function of the immune system.
Siberian ginseng is used to prevent colds, the flu, and respiratory tract infections.
Some people claim it increases stamina and endurance. A group of compounds in the herb, the eleutherosides, are thought to be responsible for its physiological effects. Like its Asian counterpart, Siberian ginseng contains polysaccharides. Proponents claim that the herb improves the way muscles use oxygen and that it helps reduce the levels of toxins in the body. Despite the use of ginseng by people of many cultures for many years, the evidence that it is effective is largely anecdotal.