Daily gargling with water appears to ward off colds among healthy people, Japanese researchers report in the November issue of the American Journal of Preventive Medicine. But an American expert is throwing cold water on the study.
The most important finding in our study is that the common cold could be prevented over 30 percent of the time by daily gargling with water, said lead author Kazunari Satomura, MD, PhD, a professor of medicine and epidemiology at Kyoto University. This simple hygienic habit could contribute to public health and it would have obvious economic benefits, he added.
The investigators enrolled 387 healthy volunteers, age 18 to 65. They were randomly assigned to gargling water, gargling with the antiseptic povidone-iodine, or receiving usual care.
The participants then led their normal lives for the next 60 days, or until they caught an upper respiratory tract infection whichever came first. They were asked to keep up with normal hand-washing and to avoid cold remedies during that time.
A total of 130 subjects contracted a cold, sore throat, sinus infection or a form of bronchitis. There was no significant difference in the rate of first infection between the control group and the povidone-gargling group. But there was a 36 percent decrease among water garglers compared to controls.
However, the results may not be as impressive as they first appear, according to Peter Muennig, MD, MPH, assistant professor at Mailman School of Public Health of Columbia University in New York.
Muennig says that while the researchers found a borderline statistically significant effect for water gargling, there was no true placebo group that is, there was no control group in which people could gargle with fake water.
Sometimes, those who believe falsely they are being treated tend to get better on their own. In this case, there was no such group, Muenning said. Because people in Japan, and Asia in general, tend to believe that (gargling) is an effective preventive modality, it is possible that the positive effect noted was due to the placebo effect.
The researchers acknowledge that participants knew which treatment they were receiving but argue that the general population believes that povidone-iodine is more effective than water, and any bias likely would have been against water.
Muennig says that the investigators report that there is no clear mechanism by which gargling reduces one's chances of getting a cold, but that they speculate that gargling might clear the throat of germs before they have a chance to spread.
If this is the case, he added, we would expect eating and drinking to do the same thing. Their claim that there is a 36 percent reduction in the chances of getting a cold with gargling must be taken with a gargle of salt.
Reference: Satomura K, et al. Prevention of upper respiratory tract infections by gargling: a randomized trial. Am J Prev Med 29(4), 2005.