Objective: Larch arabinogalactan (ResistAid * ) may prevent cold infections due to its immune-stimulatory properties. In a placebo-controlled, double-blind, randomized clinical trial, the effect of a proprietary larch arabinogalactan preparation on the incidences of common colds and its effect on cold symptoms, as a well established model for immune function, was compared to placebo.
Research design and methods: A total of 199 healthy participants who had a self reported cold infection rate of three in 6 months were randomly assigned to receive a total of either 4.5 g of an arabinogalactan preparation (n = 101) or placebo (n = 98) over a period of 12 weeks.
Main outcome measures: The participants documented each common cold episode in a diary, and rated 10 predefined infection symptoms on a 4 point rating scale during an infection period, resulting in an infection score. The common cold episodes were confirmed by medical doctors.
Clinical trial registration: ISRCTN41183655.
Results: In the full analysis set (FAS), arabinogalactan tended to decrease the incidence of common cold (p = 0.055). The number of participants affected by a cold was significantly reduced by arabinogalactan supplementation (p = 0.038). Concerning the per protocol (PP) collective, the incidences of common cold (p = 0.040) and the number of participants affected by the infection (p = 0.033) were significantly fewer after arabinogalactan compared to placebo consumption. The severity of symptoms at episode start as experienced by the participants was significantly higher after arabinogalactan supplementation (p = 0.028). The treatment was well tolerated with no significant differences between the study groups.
Conclusion: The present study demonstrated that larch arabinogalactan increased the body's potential to defend against common cold infection. While the immunomodulatory effect of arabinogalactan can be assumed, its mechanism of action remains to be elucidated.