Exercise Helps Shrink Tumors and
Combats Cancer in Many Ways
March 04, 2016
By Dr. Mercola
Compelling evidence suggests
exercise is an important component of
cancer prevention and care; slashing your risk of developing
cancer, improving your chances of successful recuperation, and
diminishing your risk of cancer recurrence.
A pattern revealed in these studies is that the longer you
exercise, the more pronounced the benefits. Studies show that both
men and women who exercise during their early years have a lower
risk of cancer later in life.
But like most things in life, exercise must also be done in
moderation and be balanced. There is a sweet spot and excessive
exercise can cause its own set of issues, but most in the U.S. are
far from being at risk for this problem.
According to a 2003 paper1
published in the journal Medicine & Science in Sports &
Exercise,"more than 100 epidemiologic studies on the role of
physical activity and cancer prevention have been published."
The authors note that:
"The data are clear in showing that physically active men
and women have about a 30 to 40 percent reduction in the risk of
developing colon cancer, compared with inactive persons …
With regard to breast cancer, there is reasonably clear
evidence that physically active women have about a 20 to 30
percent reduction in risk, compared with inactive women.
It also appears that 30 to 60 min.· of moderate- to
vigorous-intensity physical activity is needed to decrease the
risk of breast cancer, and that there is likely a dose-response
relation."
Adrenaline-Dependent Immune Cells Shrink Tumors
Most recently, research2,3,4
published in Cell Metabolism showed that active mice experienced a
50 percent reduction in tumor growth compared to inactive mice. The
mechanism behind this rather remarkable occurrence is thought to be
related to the rush of adrenaline that occurs during high intensity
exercise.
The adrenaline helps circulate natural killer (NK) immune cells
into tumors in the lung, liver, and skin, where they go to work to
kill off and eliminate the cancerous cells.
To test this theory, the researchers injected mice with
adrenaline. As predicted, they found that this caused NK cells to
move into the bloodstream, and when a tumor was present, the NK
cells would infiltrate it.
Then, to confirm the link between NK cells and tumor shrinkage,
they used specially bred mice that do not have NK cells. In these
mice, exercise had no effect on the tumors.
Blocking the flow of adrenaline had the same effect — the tumors
remained, even when the mice exercised. As reported by Medical News
Today:5
“The link between adrenaline-dependent mobilization of NK
cells and tumor infiltration was identified as the immune
signaling molecule, IL-6. Muscle tissue is known to
release IL-6 during exercise.
What surprised the researchers was that
adrenaline specifically called for IL-6 sensitive NK cells, and
that the IL-6 molecules help to guide the immune cells to the
tumors.” [Emphasis mine]
Exercise Is Potent Cancer Prevention
While the exact risk reduction varies from study to study, the
literature consistently show that exercise helps reduce your risk of
a variety of different cancers, and often to a significant degree.
Men who stayed fit in middle age had a 55 percent lower
risk of lung cancer and a 44 percent lower risk of bowel
cancer after the age of 65.
High levels of cardiorespiratory fitness (CRF) in middle age
also helped the men survive cancer, reducing their risk of
dying from lung, bowel and prostate cancer by nearly
one-third (32 percent).
Cancer Epidemiology, Biomarkers & Prevention,20158,9,10
Women with a history of exercising for an average of
1.33 hours per week during their teen years had a 16 percent
lower risk of dying from cancer, and a 15 percent lower
all-cause mortality risk.
Those who were active as teens and kept up their exercise
habit as adults had a 20 percent lower risk of death from
all causes.
Journal of the National Cancer Institute, 201511,12
Aerobic exercise slowed the growth of breast cancer
tumors in mice. By increasing tissue oxygenation, it also
improved the effectiveness of chemotherapy.
A systematic review of seven cohort studies and 14
case-control studies found that physical activity reduces
the risk of breast cancer, particularly in post-menopausal
women.
Mice who exercised on a motorized treadmill for an hour
each day, five days a week for 32 weeks, experienced fewer
incidents of liver cancer (hepatocellular carcinoma) than
sedentary mice.
Exercise was shown to alter T cells to a more effective
disease-fighting form, called "naïve" T cells, which boosts
the ability of your immune system to fight emerging and
existing cancer cells. This helps explain why exercise is
beneficial both for cancer prevention and treatment.
Cancer Epidemiology Biomarkers & Prevention, 200916
Weight training cut men’s risk of dying from cancer by
40 percent.
Women who were active at home during the day, engaging
in heavy lifting or carrying rather than mostly sitting, had
a 38 percent reduced risk of invasive breast cancers.
Exercise Improves Cancer Survival Rates and Cuts Recurrence
Should you end up with cancer, don’t fall for the old myth that
rest is the best medicine. On the contrary, exercise has been shown
to significantly boost your chances of recovery and survival.
For example, a 2005 Harvard study19
found that breast cancer patients who exercised moderately for three
to five hours a week lowered their odds of dying from cancer by
about half, compared to sedentary patients. In fact, any amount of
weekly exercise increased a patient's odds of surviving breast
cancer to some degree, and this benefit remained constant regardless
of whether women were diagnosed early on or after their cancer had
spread.
Exercise has also been shown to minimize the side effects of
conventional cancer therapy, and improve cancer patients’ quality of
life.
A recent analysis20,21
of 16 studies found that across the board, cancer patients assigned
to an exercise program consistently report significantly better
quality of life compared to those in the non-exercising control
groups, including higher self-esteem and physical functioning, less
fatigue, reduced length of hospital stays, and fewer doctor’s
visits.
Some cancer organizations now promote exercise as part of
standard cancer care, although this information has yet to fully
filter down into general oncology. Two examples of organizations
that promote exercise for cancer patients are the Macmillan Cancer
Support organization in the U.K. and Johns Hopkins22
in the U.S. Both encourage cancer patients to exercise for
2.5 hours per week.
Exercise also lowers your odds of cancer recurrence once you’ve
successfully recuperated. A study published in 2012 found that
breast and colon cancer patients who exercised regularly had half
the recurrence rate compared to non-exercisers.23
Exercise Combats Cancer in Many Ways
Exploring the relationship between exercise and cancer, a study24
in the British Medical Journal found that exercise affects several
biological functions that may directly influence your cancer risk,
including changes in energy balance, immune function, antioxidant
defense, DNA repair, and hormone levels.
Indeed, there’s not just one mechanism responsible for its
cancer-fighting effects. There are many, starting with the fact that
exercise decreases your insulin resistance, which is a profoundly
effective strategy to reduce your cancer risk. By creating a low
sugar environment, you strongly discourage the growth and spread of
cancer cells.
This is also one of the reasons why a
high-fat diet tends to discourage cancer. A key point to
remember is that while normal cells can use either glucose or
ketones derived from fat as fuel, cancerous cells lack this
metabolic flexibility and need glucose to survive and multiply. Cut
off their supply of fuel, and you effectively starve the cancer
cells to death.
Exercise, by lowering your blood sugar levels and normalizing
your insulin sensitivity, has a similar effect — it essentially
creates an environment that is less conducive to cancer growth.
Exercise also helps you shed excess fat and maintain a healthy
weight (this is particularly true for
high-intensity interval training). Excess weight is a
significant risk factor, and obesity is responsible for an estimated
500,000 cancer cases worldwide each year.25
The link between obesity and cancer is primarily hormone-driven, as
fat cells produce excess estrogen.
This also helps explain why exercise during childhood reduces
your lifetime cancer risk, and why obese children are at a
significantly heightened risk of cancer in their adult years.
Physical activity also improves circulation, driving more oxygen
into your tissues, and circulating immune cells in your blood. By
improving blood flow to your liver, it also helps your body detoxify
potentially harmful substances, including excess estrogen that may
spur estrogen-sensitive cancers.
The Metabolic Theory of Cancer
Perhaps most importantly, exercise promotes
mitochondrial health. Mitochondrial damage can trigger genetic
mutations that can contribute to cancer, so optimizing the health of
your mitochondria is a key component of cancer prevention. In fact,
mitochondrial dysfunction is at the core of virtually all
diseases.
By forcing your mitochondria — those little power stations that
produce ATP in your cells — to work harder, your mitochondria start
making reactive oxygen species (ROS), which act as signaling
molecules. One of the functions they signal is to make more
mitochondria.
So, when you exercise, your body will respond by creating more
mitochondria to keep up with the heightened energy requirement.
Travis Christofferson’s book, "Tripping Over the Truth: The Return
of the
Metabolic Theory of Cancer Illuminates a New and Hopeful Path to
a Cure" goes into all of this in great detail, and is a must-read
for anyone interested in preventing or recovering from cancer.
Exercise stimulates AMPK and SIRT1, which secondarily inhibits
mTOR, which then stimulates mitochondrial biogenesis and mitophagy,
both of which are deadly to cancer. In essence, cancer can be viewed
as a metabolic disorder, and the key to prevention and recovery lies
in restoring mitochondrial function and increasing
mitochondrial numbers. Exercise helps you do both.
Also, besides creating an environment that discourages cancer
growth, another reason why nutritional ketosis works so well for
cancer is because it too boosts mitochondrial function and drives
down inflammation.
Exercise Improves Your Odds of a Long and Healthy Life
If you want to prevent disease, exercise! Cancer is just
one of a very long list of health problems that can arise as a
result of
chronic inactivity. Your metabolic and cardiovascular health is
also largely dependent on exercise. In fact, one of the primary
benefits of exercise is that it improves your insulin and leptin
sensitivity and boosts your mitochondrial health, both of which play
decisive roles in cancer and other chronic diseases.
Ideally you’ll want to establish a
comprehensive exercise program that includes
high-intensity exercises and
strength training — both of which have been shown to be of
particular benefit for cancer prevention. I also urge you to
consider walking more, in addition to your regular workout
regimen. Aim for about 7,000 to 10,000 steps (or about an hour-long
walk) per day.
Also, avoid sitting as much as possible. If you can, limit your
sitting to three hours a day or less, as the mere act of standing
triggers beneficial changes in your biology.
Naturally, if you have cancer or any other chronic disease, you
will need to tailor your exercise routine to your individual
circumstances, taking into account your fitness level and current
health. If at times you find you need to exercise at a lower
intensity, or for shorter durations, don’t be discouraged. Always
listen to your body and if you feel you need a break, take time to
rest.
Just know that exercising for even just a few minutes a day is
better than not exercising at all, and you'll likely find that your
stamina increases over time, allowing you to complete more
challenging workouts. If your immune system is severely compromised,
you may want to exercise at home instead of visiting a public gym.
But, remember that exercise will ultimately help to boost your
immune system, so it's very important to continue with your program
even if you suffer from chronic illness or cancer.