Ginseng is a very popular herbal supplement, and is used for a host of problems. These can range from improvements in memory, poor concentration, fatigue, hypotension, problems associated with aging, mild depression, and even giving birth!
There are two types of ginseng that are used medicinally. Panax ginseng is also known as Asian ginseng. It is this variant that has a long history of use in China and other Asian countries. American ginseng is not considered as effective as Panax ginseng, though it may suit some people better.
Siberian ginseng is actually not in the same genus as Panax and American ginseng, and its active constituents are also quite different. Thus, even though it is nicknamed 'ginseng', it is actually not a ginseng. To get a sense of the differences in plant classification that a genus represents, look at the term 'homo sapien', as applied to humans. The genus is represented by the term 'Homo'. 'Sapiens' is used to name the species. Both American and Asian ginseng belong to the same genus - 'Panax'.
Another important difference between Siberian 'ginseng' and the Panax varieties, is that Siberian ginseng does not contain ginsenosides. Ginsenosides are found only in plants belonging to the Panax genus. They are believed to be responsible for ginseng's medicinal effects, and there are a number of different variants that have slightly different effects. The exact amounts of the different ginsenosides predominant in various ginseng plants does vary - even from plant to plant. Things like where the plants were grown, and how old they were when they were harvested, can all have an impact on their ginsenoside content. For this reason, it really pays to get good quality ginseng, whether it's the American or Asian variety you're after.
Whilst there have been problems of credibility associated with some ginseng studies, possibly related to the variety in strength and quality of the supplements used, there have been good quality studies as well.
Ginseng For Colds
One study, from the University of Western Ontario and the University of Alberta, was designed as a placebo controlled, randomized, double blind study of 170 people between the ages of 18 and 65 years. This is considered a good-quality study design amongst scientists. They used a standardized extract of American ginseng, which came in a 200g capsule, with 80% poly-furanosyl-pyranosyl-saccharides from the root.
The people in the study had a history of getting at least 2 colds in the previous year. They were told to take 2 capsules of either ginseng or the placebo (they didn't know which they were getting), every day for 4 months. The trial started at the beginning of the cold and flu season.
The results were interesting. Of those taking ginseng, only 10% got two or more colds, compared to 22.8% of those taking the placebo. This was comparable with the results of common antiviral drugs that are used to prevent or treat flu. And of those who took the ginseng but still got sick, their symptoms were less severe.
Thus ginseng may provide a valuable immune boost to those who are susceptible to winter colds. This is especially valid for the elderly, as ginseng has been shown to have other important benefits for memory and aging.