In this study Predy and colleagues randomized 323 study subjects to receive a proprietary ginseng ( Panax quinquefolius ) preparation or a placebo and followed them for 4 months during the winter (September to April). Using predetermined criteria to determine if subject-reported symptoms were "colds," the authors found that ginseng reduced the frequency of colds. Subjects in the ginseng group reported having 2 or more colds less often than subjects in the placebo group (10% v. 23%). Symptom severity and duration were also lessened.
In a related commentary, Ronald Turner of the University of Virginia School of Medicine recently evaluated Echinacea angustifolia as a preventive herbal product for the common cold (and found it did not work). He cautions physicians and the public about the difficulties of doing clinical studies of common viral infections, especially when the specific viruses are not identified.
p. 1043 Efficacy of an extract of North American ginseng containing poly-furanosyl-pyranosyl-saccharides for preventing upper respiratory tract infections: a randomized controlled trial
-- T.K. Basu et al
http://www.cmaj.ca/misc/press/pg1043.pdf
p. 1051 Studies of "natural" remedies for the common cold: pitfalls and pratfalls
-- R.B. Turner
http://www.cmaj.ca/misc/press/pg1051.pdf
Journal
Canadian Medical Association Journal