The patients who received ginseng had a lower incidence of influenza and colds, higher antibody titers, and higher natural killer cell activity levels. Also know as an adaptogen (a substance that helps the body fight stress) it has been shown to shorten the duration of a cold. One study used 200 mg of ginseng extract a day for four months and found a reduction in the length of symptoms. Another study found that ginseng may prevent influenza-caused acute respiratory illness (ARI) in elderly patients.
Dosage: Extract -200 mg per day of extract, or dry root (tea) up to 2 mg per day.