Exercise Prevents
Cancer By Promoting Cell Death - Both Skin and Bowel Cancer Studies Show
Voluntary Workouts Reduce Risk
May 13th 2006
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Skin cancer |
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Two studies highlight the benefits of exercise, including lower risks of
skin cancer and bowel cancer. In the first study, published in the
journal Carcinogenesis, exposed female mice to ultraviolet B light (UVB).
The researchers found that the mice that had 24-hour access to running
wheels took longer to develop skin tumors and had fewer of them. The
tumors were also smaller in the mice that were exercising.
Scientists believe that programmed cell death, called apoptosis, can be
triggered by exercise. The problem with cancer cells is that they do
not die like normal cells. Dr. Allan Conney said “Preliminary
indications from follow-up work in the laboratory suggest that voluntary
exercise enhances UVB-induced apoptosis in the skin, and that it also
enhances apoptosis in UVB-induced tumors. So, although UVB is triggering
the development of tumors, exercise is counteracting the effect by
stimulating the death of the developing cancer cells.” Dr. Conney is
Garbe professor of Cancer and Leukemia Research.
Most people may be surprised that exercise promotes cell death. Dr.
Conney adds “Our studies may be the first to suggest an apoptotic
mechanism for the effect of voluntary exercise in the development of
cancer. In addition, we found that voluntary exercise decreased body fat
and that the number of tumours decreased with decreasing amounts of fat.
This effect may also play an important role in the mechanism and
warrants further investigation, bearing in mind the growing rates of
obesity in the Western world, particularly in the USA and UK."
Researchers found that voluntary exercise and a restricted diet in male
mice helped prevent pre-cancerous polyps in the intestines, and the
number and size of polyps. They found that exercise also improved
survival.
Even more interesting was the wording of the bowel cancer research. Dr.
Lisa Colbert believes that a “negative energy balance”, produced by
increasing the mice's energy output (by use of a running wheel) while
maintaining a restricted calorie intake, appeared to be the important
factor in inhibiting the growth of polyps in the intestines. Dr.
Colbert is the Assistant Professor at the University of
Wisconsin-Madison.
She says that “"Negative energy balance was indicated by a lower body
weight among the exercising mice, although they retained more body fat
at the end of the study than the non-exercising mice – an observation
that might be due to the fact that the exercising mice were healthier,
while the health of the non-exercising mice was beginning to decline due
to higher numbers of polyps. There were higher levels of hormones known
to be associated with the onset of cancer – insulin-like growth factor-1
(IGF-1) and corticosterone – amongst the exercising mice, but this did
not correlate with higher total polyp numbers. These data suggest that
voluntary exercise that induces a negative energy balance protects
against the onset of cancer in these mice, but that the mechanism is
unlikely to be related to body composition, IGF-1 or corticosterone."
Scientists are still not sure what the exact mechanism is for reducing
the incidence of cancer, but earlier research showed that physically
active people have a reduced risk of developing the disease.
Dan Wilson
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