The Web site for the Atlanta-based Centers for Disease Control and Prevention (CDC) contains a pandemic influenza storybook filled with personal reflections from survivors, family members and friends. One of the accounts tells the story of Art McLaughlin, who lived about 25 km east of Chicago during the 1918 flu pandemic in a town where guards were posted on every block to keep people from moving around and transmitting the virus. What distinguishes McLaughlin’s story from others, however, is the fact that McLaughlin credits his family’s survival of that horrific pandemic to bathing and frequent gargling with a popular antiseptic that can be found in most drugstores today — Listerine.
In fact, McLaughlin was so convinced of the preventive effects of Listerine that he gargled with it every day for the rest of his life. Yes, as odd as it may sound to some, this man gargled as a preventive measure against disease.
Nearly one century after the Spanish flu pandemic took the lives of 50 million to 100 million people, much of the public in certain countries, particularly Japan, is still gargling in an effort to prevent ailments ranging from the common cold to the flu. In fact, in May of this year, Japan’s own Ministry of Health, Labor and Welfare implemented a national campaign to control the outbreak of the H1N1 swine flu by encouraging the public to wash their hands and, yes, to gargle.
Information released by the ministry recommends gargling “to avoid contracting influenza,” and gargling “to prevent the infectious outbreak from growing and spreading.” The CDC’s own prevention measures don’t mention gargling, but they do suggest that you avoid touching your eyes, nose and mouth, something conspicuously left off the MHLW’s recommendations.
So what’s behind this recommendation to gargle?
As the holiday season approaches and so many prepare to board congested planes, trains and buses on journeys to visit loved ones, let’s examine the science behind this recommendation to gargle to determine whether it is actually effective as a preventive measure against cold and flu viruses.
Much of the research on this topic has been done by a group of scientists who call themselves the Great Cold Investigators, an informal group of Japanese health professionals — mainly physicians — who seek to resolve clinical questions about the common cold.
In fact, in the Sept. 14, 2007, issue of Internal Medicine, this team published findings that address the very question we ask. The research is titled “Can We Prevent Influenza-like Illnesses by Gargling?” and basically consists of further analysis of an earlier trial. The conclusion is particularly worth noting: “We could not demonstrate significant preventive effects of gargling against influenza-like illnesses.”
No “significant preventive effects”? Then why in the world is the MHLW recommending that people gargle to avoid contracting the flu? Mostly because of custom and the earlier trial on which these findings are based.
That earlier trial, the first randomized controlled trial to evaluate the effectiveness of gargling for the prevention of upper respiratory tract infections among healthy people, was carried out by the Great Cold Investigators in the 2002-2003 winter season and analyzed in 2003 and 2004. The findings were published in the November 2005 issue of the American Journal of Preventive Medicine.
Upper respiratory tract infection, often abbreviated as URTI, includes the common cold, influenza, laryngitis (inflammation of the voice box), pharyngitis (sore throat), sinusitis, tonsillitis and croup (inflammation of the trachea and larynx in children). URTI symptoms can range from mild for cold suffers (sneezing, coughing, runny nose, congestion, headache and sore throat) to more serious for those with influenza (high fever, headache, chills, body aches, weakness and fatigue).
The 2002-2003 trial took 387 healthy volunteers aged 18 to 65 years old from all over Japan and randomly assigned them to one of three groups: (1) a group that gargled three times a day with tap water; (2) a group that gargled three times a day with a commercially available antiseptic — diluted povidone-iodine in this case; and (3) a control group instructed to retain their previous gargling habits.
Over 60 days, 34 of 122 (27.9 percent) that gargled with water recorded symptoms of a URTI, as did 46 of 132 (34.8 percent) that gargled with the antiseptic and 50 of 130 (38.5 percent) in the control group. (Three participants were removed from the trial for various reasons.)
The team then concluded the following: “Simple water gargling was effective to prevent URTIs among healthy people. By contrast, gargling with povidone-iodine did not significantly reduce URTI incidence.”
As for the flu, 12 subjects (9.8 percent) in the water-gargling group came down with an influenza-like disease, compared with 11 (8.3 percent) in the antiseptic-gargling group and 14 (10.8 percent) in the control group. These results were later analyzed, and as mentioned earlier, the conclusion published in 2007 proclaimed gargling to show no significant preventive effect.
However, when we review this entire trial a bit more critically, concerns arise about any URTI claim. For example, 72 percent of those in the control group actually did gargle with either water or antiseptic. And they gargled on average more than once a day. Why? Well, they were instructed to keep doing what they normally did, and they typically gargled. According to Dr. Takashi Kawamura, who chairs the Great Cold Investigators, because Japanese consider gargling to be effective, prohibiting the control group from doing such seemed “somewhat unethical.”
Another concern about this trial is that 22 percent of the gargling done in the antiseptic group was done with water because participants were told to switch to water if the antiseptic caused any discomfort.
More disturbing, however, compared with the water- and antiseptic-gargling groups, the control group was filled with 5.5 and 7.3 percent more volunteers from the northern areas of Japan, where subjects were 1.7 times more likely to contract a URTI than one of the subjects from central Japan.
Finally, subjects in the water-gargling group simply washed their hands more than those in the other two groups.
Some people may wonder how a simple act such as swishing a little water around your mouth can ever possibly prevent a URTI from occurring. The theory is that intermittent gargling can disrupt the propagation of a virus causing a URTI. Viruses, however, are known to bind to specific receptors of the cell, and according to Kawamura, “It is unlikely that pathogenic viruses are washed out by turbulent waters of occasional gargling. Instead, some proteases that aid viral infection would be easily removed from the oral cavity by oral hygiene.”
In layman’s terms, gargling might help remove enzymes that may cause influenza viruses to become more infective.
Other studies have been done that suggest a benefit to gargling tea, but most of them appear to suffer from the fallacy of small numbers.
In the 2005-2006 winter season, a trial was conducted in Japan to determine the effects of gargling with tea catechin extracts on the prevention of influenza infection in healthy adults. Only two of the 195 participants in the catechin group came down with influenza over the 90-day study, but only four of the 200 in the control group did too. Conclusion: “We could not find significant effects of gargling with tea catechin on prevention of influenza in healthy adults.”
One year earlier though, that same team conducted a similar trial, except this time the subjects consisted of 124 elderly Japanese, each at least 65 years old. This time, one of 76 in the catechin group and five of 48 in the control group contracted influenza, in what was concluded to be the “first reported study demonstrating the effect of catechin gargling on the prevention of influenza infection in the elderly.”
Interestingly, a quick search of the Internet brings up many sites that use the earlier trial to support claims of the preventive effects of tea against influenza, while completely ignoring the more recent trial, which was conducted by the exact same team, included far more subjects, and did not demonstrate any significant impact at all.
It should also be noted that these tea catechin studies were funded by a grant from the MHLW and overseen by two researchers from the University of Shizuoka, a public school situated in a prefecture economically dependent on tea growth, and a researcher for Mitsui Norin Co. Ltd., which sells tea catechin extract.
Now, what has been shown to be effective against the spread of viruses? Creditable studies point to advice that has traditionally been handed down by parents: Sleep appears to boost immunity; moderate exercise seems to do the same; and, of course, washing your hands for 25 seconds with soap and water works wonders — and studies show that the temperature of the water doesn’t even matter.
Moreover, because hand-to-face contact is responsible for so much infection, keeping your fingers out of your eyes, nose and mouth greatly reduces your risk, in addition to keeping away from others who are infected.
In Japan, however, late nights at the office followed by “domestic consumption” out on the town is the behavior expected of many, and this lifestyle is often sandwiched between commutes that can be far too close for comfort. Therefore, traditional advice encouraging more sleep, exercise and avoidance of the infected might be a little hard for many to follow.
But as the weather cools down and holiday travel heats up, all of us would be wise to practice healthy habits. Whether those habits include gargling is up to you.
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