Though the holidays have passed, it's still the season for sniffles, sore throats and the flu. Several recent studies have found that people who exercise on a regular basis, get sick 50% less than those who don't exercise. The American College of Sports Medicine, a leading authority on exercise, says there is no medicine, pill or supplement that comes close to the protection exercise provides against illness. Exercise strengthens your immune system with natural cells that fight viruses. 30 minutes of exercise, 5 days a week, can help protect you from colds and flu.