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Getting
Physically Active May Increase Your Chances of Surviving Cancer
From
Environmental Nutrition
March
2007
By Hillary Wright, M.Ed., R.D.
More than 10 million Americans are cancer survivors. Most are anxious
to do anything they can to reduce the risk of a recurrence. But
what can be done?
While research abounds on how diet and lifestyle habits affect the
initial appearance of cancer, far fewer studies have looked at how
to stay healthy and prevent cancer’s return following treatment.
Preventing
Cancer From the Start. It’s well accepted that diet and physical
activity influence your risk of developing cancer. According to
the American Institute for Cancer Research, eating a plant-based
diet plays a pivotal role in preventing tumor growth and in slowing
its progression. Studies also have found that people who exercise
have a lower risk of developing certain kinds of cancer, such as
cancers of the breast and colon.
Overweight and obesity increase the risk of some types of cancer.
Because regular activity can help with weight management, it logically
follows that it plays a role in preventing cancer too.
Preventing
Cancer From Coming Back. Studies have only recently begun to look
at the effect of diet and exercise on the recurrence of cancer.
Researchers have found that eating a nutrient-loaded, plant- based
diet after cancer diagnosis and treatment may lessen the likelihood
of recur rence or of developing a second cancer.
Likewise, leading an active lifestyle is strongly linked not only
to a lower likelihood of getting cancer, but preliminary research
suggests that exercise may actually reduce the risk of some cancers
recurring, unrelated to its effect on weight (see “Exercise
to Keep Cancer at Bay,” above right).
According
to colon cancer researcher Jeffrey Meyerhardt, M.D., M.P.H., of
Harvard Medical School, because a sedentary lifestyle is most strongly
tied to an increased risk of developing breast and colon cancers,
those two cancers are now the focus of much of the research on exercise
and cancer recurrence. But researchers are optimistic that future
studies will expand the list of cancers for which physical activity
might decrease the likelihood of recurrence.
Here’s what we know so far about how activity affects these
two cancers.
Exercise
and Breast Cancer. Two studies have followed breast cancer survivors,
many of whom become sedentary during treatment and never resume
their pre-diagnosis activity levels. The Harvard Nurses’ Health
Study, which included almost 3,000 women with cancer, concluded
that regular exercise after a breast cancer diagnosis may ultimately
reduce the risk of death from the disease, particularly in women
with hormone-sensitive tumors (which grow in response to higher
hormone levels).
“We
know from past research that active women have lower sex hormone
levels than inactive women, which may suppress breast cancer growth
and recurrence,” says lead researcher Michelle Holmes, M.D.,
of Harvard Medical School. In the study, as expected, women with
hormone-sensitive tumors benefited the most from exercise.
The
greatest benefit occurred in women who exercised the equivalent
of walking three to five hours per week at an average pace. They
experienced half the risk of recurrence of women who exercised less
than one hour a week. That’s consistent with what the U.S.
Dietary Guidelines for Americans recommend for lowering the risk
of cardiovascular disease, diabetes, osteoporosis and other chronic
illnesses. Higher levels of activity didn’t confer any additional
benefit.
Another study of exercise and breast cancer survivors by Page Abrahamson,
Ph.D., of the University of North Carolina at Chapel Hill, analyzed
whether levels of activity before diagnosis influenced survival
in a group of 1,263 women with invasive breast cancer.
The
results? High levels of activity (the equivalent of walking 11 hours
or more per week) in the year before diagnosis were associated with
a 30% increase in breast cancer survival among overweight and obese
women, compared to those who exercised less than one hour a week.
No such link was found for women of normal weight.
Overweight
women with breast cancer typically suffer higher death rates. Adding
activity may be one way to increase the chances for long-term survival.
Exercise
and Colon Cancer. Harvard’s Meyerhardt and colleagues at the
Dana Farber Cancer Institute in Boston have conducted two studies
of exercise and colon cancer recurrence.
In the first study, researchers evaluated the activity levels of
832 patients six months after surgery and chemotherapy for stage
III colon cancer. They found that participants who exercised the
equivalent of walking six or more hours per week at an average pace
were only half as likely to suffer a recurrence compared to those
who exercised less than one hour a week. Moreover, physical activity
was linked to fewer deaths from all causes.
The
team also studied 573 survivors of colon and rectal cancers from
the Nurses’ Health Study and found a similar protective benefit
of exercise on cancer-related deaths and all other deaths.
Exactly how exercise might improve survival from colon cancer remains
unclear. According to Meyerhardt, less recurrence is likely related
to exercise’s ability to lower levels of substances known
to drive cancer cell growth, such as insulin and insulin-like growth
factor. Physical activity has also been associated with lower circulating
levels of the inflammatory markers C-reactive protein and interleukin-6;
high levels have been associated with increased cancer risk.
The
Bottom Line. Although research on the role of physical activity
in cancer recurrence is still evolving, it appears that exercise
is beneficial, at least for breast and colon cancers. Moreover,
leading an active lifestyle is critical for preventing obesity,
which is a risk factor for a number of cancers, including cancers
of the breast, colon, uterus and kidney.
Despite
countless well-known health benefits of exercise, recent studies
show that more than 60% of Americans are not active enough. For
cancer survivors, a comprehensive long-term wellness plan should
include a healthful diet, weight control and regular exercise, not
only for upping the odds of staying cancer-free, but for reducing
the risk of other chronic health threats, like cardiovascular disease
and diabetes.
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