According to new research people who take ginseng suffer from far fewer colds.
Canadian researchers say that in a study only one in 10 of those given daily doses of North American ginseng root extract suffered two or more colds during four months including winter, compared with almost a quarter of those taking placebos.
Previous attempts to test scientifically claims of a range of health benefits attributed to the herb, including combating flu and colds, have been of poor quality.
This encouraging news aptly follows a Meteorological Office warning a week ago that the coming winter is likely to be significantly colder than average.
Dr Tapan Basu, of the University of Alberta, who led the study, says a moderate dose of extract of the root of North American ginseng was associated with an absolute risk reduction of recurrent colds, as well as a reduction in the mean number of colds per person.
Basu says the total symptom score was 31 per cent lower and the total number of days symptoms were reported 34.5 per cent less in the ginseng group than in the placebo group.
Apparently the ginseng extract was also found to be effective in the reducing of the severity of symptoms and the number of days symptoms relating to colds were reported.
In the study a group of 130 people aged 18 to 65 from Edmonton, Canada, who said they had suffered from at least two colds the previous year, took capsules of ginseng extract twice a day for four months over the winter.
Meanwhile another group of 149 individuals was given placebos during the same period.
Participants did not know which group they were in.
It was found among those who took ginseng, the proportion who caught two or more colds in the four months was 10 per cent and the average number of colds was 0.68.
In the control group, 23 per cent had two or more colds and the average number of colds was 0.93.
Active constituents of ginseng have been shown to improve the immune system by stimulating the production of immunoglobulin - proteins that bind to foreign substances such as bacteria when they invade the body.
Most adults catch two to five colds a year, and young children represent the main reservoir of common cold viruses, with nurseries and schools being prime infection centres.
Although more people catch colds and flu during colder weather, there is no scientific consensus on why this is so, but one novel theory is that breathing in cold air lowers resistance to infection.
In an earlier study involving 256 people and reported at the National Institute of Mental Health conference in Florida, it was suggested that a combination of ginseng and another herb, ginkgo, enhanced memory and reduced mental fatigue.
The research is published in the Canadian Medical Association Journal.