Stress (like training for and running races), can reduce defenses your immune system provides.
In a study of sedentary, recreation, and elite athlete runners, the three groups had about the same rate of upper respiratory illnesses; however, the recreational runners had fewer instances of sickness.
The conclusion was that moderate exercise reduced the risk of infection while no exercise or intense training seems to increase the risk of getting sick. In fact, light to moderate training seems to even provide a boost to the immune function.
But where is the break between recreational and elite? The study showed 20 miles and over per week seems to be the optimal point at which the immune system was affected.
To keep your immune system running at an optimal level, keep an awareness of these things:
1) Avoid overtraining:
Overtraining results when recovery between workouts (repeatedly) does not happen or is not long enough. Most training plans have enough recovery time built into them, but if you skip parts of your plan or push too hard, it can happen. Symptoms include elevated heart rate when resting, moodiness, susceptibility to sickness and trouble sleeping.
2) Get adequate sleep:
Chronic sleep deprivation is linked to a drop in one’s immune system as a result of several studies. With less sleep over time, metabolic and hormonal levels start to change, Cortisol increases and glucose tolerance decreases, both affecting how the body processes food to glycogen – a really important function when competitive running.
3) Eat a healthy diet:
Most seasoned runners know their unique nutritional needs; however not necessarily to new runners. What competitive runners eat before, during and after running at various stages in their training plan not only affects performance but their health.
A diet rich in complex carbohydrates (rate of 3 to 5 grams per pound of body weight) replaces and builds up the glycogen stores while protein (1.4 to 1.7 grams per kilogram of body weight) is necessary to rebuild and repair muscle.
Finally, be sure to keep properly hydrated by monitoring the color of your urine. It should be light yellow. Be cautious of clear urine, it could indicate over-hydrating which can cause an imbalance of electrolytes.
Statistically, your risk for catching more colds and upper respiratory illnesses increases when you move from recreational to competitive running, however, by following these tips you should be able to keep it at a manageable level.