Nutrition, Training and Immune Function: Can Exercise Keep You From Getting Sick?
David C. Nieman, Dr. P.H., Director of the Human Performance Lab, Appalachian State University,
The relationship between exercise and sickness, especially the common cold, evokes considerable interest among athletes, coaches and athletic trainers. Many are convinced that regular moderate training can protect against illness, while others feel that too much exercise will lower immune levels.
Can Moderate Exercise Help Prevent Colds?
Research shows that several positive changes occur in the immune system as a result of regular exercise:
- Moderate exercise lowers stress hormones; stress hormones can suppress immunity.
- People who exercise report fewer colds than those who are sedentary.
- Near daily exercise cuts the number of sick days in half during a 12- to 15-week period.
Although the immune system returns to pre-exercise levels very quickly after exercise, each workout represents a boost to the immune system that appears to reduce the risk of infection over the long term.
Can Too Much Exercise Increasethe Risk for Colds?
While studies show exercise may reduce the risk of colds, there may also besome validity to the common perception that heavy exertion lowers resistance to illness. Studies have also shown a steep drop in immune function lasting anywhere from six to 72 hours in athletes after they ran for two to three hours.1 Much of this immune suppression appears to be related to the elevation of stress hormones, which are secreted in high quantity during and following heavy exercise. Other studies have shown that sickness rates climb following marathons and over-training.
Guidelines for Reducing Risk
While training hard for competition must be part of theathletes’ experience, an increased risk for infection does not have to be. There are several practical recommendations athletes can follow to minimize the impact of stress on the immune system:
- Keep life stresses to a minimum.
- Eat a well-balanced diet to keep vitamin and mineral pools at optimal levels. (Contrary to popular opinion, vitamin C and E supplements do not counter immune suppression.)
- Avoid over-training and chronic fatigue (and get ample sleep on a regular schedule).
- Avoid rapid weight loss.
- Refrain from touching the eyes and nose.
- Get a flu shot if competing in the winter.
- Use carbohydrate beverages before, during and after endurance events or unusually heavy training bouts. Studies indicate that a carbohydrate beverage (about one quart per hour of heavy exercise) causes higher bloodsugar levels, less suppression to the immune system and lowers stress hormone production when compared to drinking water alone.
David Nieman, DR P.H. is the director of the Human Performance Lab at Appalachian State University in Boone, N.C. He can be reached at email@example.com.
Reprinted from the September 2003 issue of Training & Conditioning
Callout: Although the immune systemreturns to pre-exercise levels very quickly after exercise, each workout represents a boost to the immune system that appears to reduce the risk of infection over the long term.
Reference: 1Nieman DC. Does exercise alter immune function and respiratory infections? President’s Council on Physical Fitness and Sports, Research Digest, Series 3, No. 13, June, 2001.