It's cold and flu season again. Time to think about how to ward off any illness. Of course you should wash your hands frequently, eat nutritiously and get plenty of sleep to keep your body in germ fighting shape but does exercise also help keep you from getting sick?
Yes! There is a considerable amount of research showing that regular (at least a few times a week) moderate exercise enhances the immune system. Exercise has been shown to increase the production of macrophages, which are a large type of white blood cell that attack the kinds of bacteria that can trigger upper respiratory diseases. Other studies show there are actually physiological changes in the immune system that happen when a person exercises. Cells that promote immunity circulate through the system more rapidly, and they're capable of killing both viruses and bacteria. Research also shows that people who work out regularly report half as many sick days because of colds or sore throats compared to people who didn't exercise.
However, studies also show that intense exercise (i.e. marathons, endurance races) can negatively affect the immune system. If you don't give your body the proper rest it needs between high intensity workouts you could be weakening your immune system.
Bottom line, moderate exercise at least three times a week has so many benefits even beyond keeping you from getting sick so make the time and do it!