A study published Monday in the British Journal of Sports Medicine reports that regular aerobic exercise may cut the risk of developing colds and other upper respiratory infections almost in half.
Researchers followed 1,002 American adults, aged 18 to 85, during a 12-week period in 2008. They found that those people who said they exercised aerobically at least 5 times a week and/or who perceived themselves as being physically fit (the study didn’t actually assess their physical fitness) had up to 46 percent fewer days with a cold or other upper respiratory tract infection than people who exercised a maximum of one day a week or who thought themselves physically out of shape.
Specifically, the exercisers spent an average of 4.41 days with an upper respiratory infection during the 12 weeks of the study versus an average of 8.18 days for the sedentary folk. In addition, when the exercisers did get an upper respiratory tract infection, their reported symptoms tended to be significantly less severe.
Aerobic exercise in the study was defined as that which increased breathing and heart rate and made people sweat for at least 20 minutes — activities such as brisk walking, cycling, swimming, basketball, racquetball and vigorous yard work.
These findings support other research showing an association between moderate exercise and a reduced risk of the common cold and other upper respiratory tract infections. Exactly how exercise may protect against these illnesses is unknown, but, as the study’s authors point out, moderate exercise triggers a temporary boost in the circulation of certain antibodies and cells involved in the body’s immune response.
At the same time, moderate exercise does not (unlike intense exercise) increase the release of stress hormones, which are suspected of suppressing immunity. (The release of these stress hormones is believed to be why runners are so susceptible to upper respiratory infections during the week or so after finishing a marathon.)
This study has its limitations. Although the researchers adjusted the data for such confounding factors as age, sex, weight, mental stress level and even fruit consumption (higher fruit intake has been linked to fewer colds), there may have been factors they missed. The first missed factor that jumped to my mind — and that the authors themselves acknowledge — is exposure to children. Parents (or other adults who are around kids a lot) are much more likely to be exposed to viruses and other pathogens — and thus more likely to get sick.
I doubt many people will start exercising solely to lower their risk of upper respiratory infections. After all, exercise offers much more significant health benefits — protection against heart disease, diabetes, depression and cancer, to name just a few. But these findings should provide us with a good incentive to keep up our exercising routine as cold weather descends.
But don’t forget to take the most important steps for cold and flu prevention: Get a flu shot and wash your hands. Often.
FYI: The study was funded by Coca-Cola and Quercegen Pharmaceuticals. After a bit of Googling, I figured out why: The authors (from Appalachian State University in Kannapolis, N.C.) acknowledge that the study had originally focused on the effects of quercetin supplements on the body’s immune function and upper respiratory infections. Quercetin, an anti-oxidant found primarily in the skin of red apples, red grapes, red onions and certain berries, has been touted as the next “super-supplement.” This study found quercetin had no influence on either immune function or upper respiratory infections — disappointing news, no doubt, for Quercegen Pharmaceuticals, which describes itself as the leading manufacturer of quercetin supplements, and for Coca-Cola, which, as the New York Times has reported, was hoping to market a new sports drink laden with quercetin.