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Extract from A Harvard Medical School Special Health Report:The Truth About Your Immune System
Exercise: Good or bad for immunity?
Regular exercise is one of the pillars of healthy living.
It improves cardiovascular health, lowers blood pressure,
helps control body weight, and protects against a
variety of diseases. But does it help maintain a healthy
immune system? And, conversely, can too much or
too little exercise depress the immune response? The
answer is that just like a healthy diet, exercise can
contribute to general good health and therefore to a
healthy immune system. It may contribute even more
directly by promoting good circulation, which allows
the cells and substances of the immune system to move
through the body freely and do their job efficiently.
Some scientists are trying to take the next step to
determine whether exercise directly affects a person’s
susceptibility to infection. In 2009, the Journal Exercise
and Sport Sciences Reviews published a review
article in which the authors suggested that intensive
exercise may suppress the immune system, while
moderate exercise improves it. But conclusive evidence
remains elusive.
Over the years, researchers have tackled this question
from many directions. For example, researchers
at Appalachian State University in North Carolina
conducted a study showing that people who walked
briskly for 45 minutes a day, five days a week for 12
to 15 weeks, had fewer cases of colds and flu than the
sedentary subjects in the study. But whether the result
was actually caused by the exercise or by other factors
remains to be proven. The American College of Sports
Medicine published a study in 2005 which concluded
that a daily 30-minute walk did not alter several measurements
of immune function.
In other research, scientists are looking at
whether extreme amounts of intensive exercise can
cause athletes to get sick more often or somehow
impairs their immune function. While some changes
in immune system components such as cytokines,
white blood cells, and certain antibodies have been
recorded, immunologists do not yet know what these
changes mean in terms of human immune response.
No one yet knows, for example, whether an increase
in cytokines is helpful or has any true effect on
immune response. Similarly, no one knows whether
a general increase in white cell count is a good thing
or a bad thing.
Do these findings apply to average people doing
moderate exercise? Does regular exercise help keep the
immune system healthy? For now, even though a direct
beneficial link hasn’t been established, it’s reasonable
to consider moderate regular exercise to be a beneficial
arrow in the quiver of healthy living, a potentially
important means for keeping your immune system
healthy along with the rest of your body.
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