By Dr. Mercola
That exercise is crucial
for optimal health is nothing new. But did you know it's also a powerful
strategy to reduce your risk for cancer? It can also improve your
chances of remission and recovery should you develop cancer.
Well over 100 studies have looked at the role of physical activity on cancer prevention1 and they reveal a distinct pattern: the longer you exercise, the more pronounced the benefits.
Studies show that people who exercise during their early years have a lower risk of cancer later in life.
The degree to which exercise cuts your cancer risk varies depending on
the type of cancer and other factors, but the data shows physically
active individuals have a 20 to 55 percent lower risk of cancer than
their sedentary peers. For example, compared to inactive people, active
men and/or women have a:
Exercise Lowers Your Risk of at Least a Dozen Different Cancers
Most recently, an analysis of 12 studies that included data from 1.4
million people of a wide range of ethnic backgrounds from both the U.S.
and Europe over the course of 11 years found that those who exercised
more had, on average, a 7 percent lower risk of developing ANY kind of
cancer. As reported by Time Magazine:7
"[T]he reduced risk was especially striking for 13 types of cancers.
People who were more active had on average a 20 percent lower risk of
cancers of the esophagus, lung, kidney, stomach, endometrium and others
compared with people who were less active ...
'Everybody knows physical activity reduces heart disease risk,' says
[lead author Steven] Moore [Ph.D.]. 'The takeaway here is that physical
activity might reduce the risk of cancers as well.
Cancer is a very feared disease, but if people understand that
physical activity can influence their risk for cancer, then that might
provide yet one more motivating factor to become active.'"
How Exercise Combats Cancer
So just how does exercise prevent cancer? Research shows there are many
pathways and mechanisms at play; a synergistic orchestra of chemical
reactions if you will, triggered by physical exertion.
When I first read about the exercise and cancer connection nearly 30
years ago, I was surprised and had no idea what the mechanism was. But
here's a sampling of what science has discovered in the last few
decades. Exercise decreases your risk of cancer by affecting:
Mitochondrial function
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.
Exercise is one of the most potent stimulators of PGC-1alpha which
stimulates mitochondrial biogenesis or production of new mitochondria.
It does this by lowering mTOR, insulin and leptin
levels which also improves mitochdondrial autophagy (mitophagy) which is
a key element of controlling malignant growth.
I review some of these details in my interview with
Travis Christofferson's about his book, "Tripping Over the Truth: The
Return of the Metabolic Theory of Cancer."
This book is a must-read for anyone interested in preventing or recovering from cancer.
AMPK, SIRT1, and mTOR
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.
Energy balance, immune function and more
Exercise affects several biological functions that may directly
influence your cancer risk, including changes in energy balance, immune
function, antioxidant defense, DNA repair, bowel motility and hormone
levels.8
Blood sugar and insulin
Exercise helps lower your blood sugar level and decrease your
insulin resistance, and by creating a low sugar environment you strongly
discourage the growth and spread of cancer cells. Sugar's ability to promote cancer
has been known since the early 1930s, following Dr. Otto Warburg's
discovery that malignant tumors exhibit an increase in anaerobic
glycolysis — a process whereby glucose is used as a fuel by cancer cells
with lactic acid as an anaerobic byproduct.
This helps explain why a ketogenic diet appears to be such a potent strategy in the treatment of many cancers.
The reason for this is because while all normal cells in your body
can use either glucose or ketone bodies from fat as fuel, cancerous
cells lack this metabolic flexibility.
Body weight
It 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.9
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.
Blood circulation
Physical activity 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.
Adrenaline-dependent killer cells
Physical activity triggers the release of adrenaline, which in
turn helps circulate natural killer (NK) immune cells into tumors in
your lung, liver, and skin, where they go to work to kill off and
eliminate the cancerous cells.
The key that allows adrenaline-dependent NK cells to
infiltrate cancer tumors is the immune signaling molecule, IL-6, which
is released by muscle tissue during exercise.
Without IL-6, the adrenaline cannot produce this anti-cancer effect,
because the IL-6 molecules are what guide the immune cells to the
tumors.10,11,12,13
T cells
Exercise alters 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.14
Non-alcoholic fatty liver disease
Regular exercise has also been shown to reduce your risk of
non-alcoholic fatty liver disease, brought on by an unhealthy diet,
thereby cutting your risk of hepatocellular carcinoma (HCC) — a cancer
that originates in your liver cells.15
Exercise Is Also Important During and After Cancer
A report by the British organization Macmillan Cancer Support16
argues that exercise is an important part of cancer care that really
should not be overlooked. They recommend all cancer patients get 2.5
hours of moderate-intensity exercise each week. Johns Hopkins in the U.S. also recommends exercise during and after cancer treatment.17
Their reasoning is well-founded, as studies show that cancer patients
who exercise can boost their odds of survival and reduce recurrence by
about 50 percent.
• Improved treatment success: Animal research suggests aerobic exercise helps boost the effectiveness of chemotherapy by increasing tissue oxygenation.18,19
Exercise also helps mitigate a number of common side effects of
chemotherapy drugs and radiation, including reducing fatigue, protecting
your heart and bone health, managing stress and anxiety, improving
sleep and appetite, and offering pain relief.
• Improved survival:
Harvard researchers found that breast cancer patients who exercised
moderately for three to five hours a week cut 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. This benefit remained constant regardless of
whether women were diagnosed early on or after their cancer had spread.20 • Reduced recurrence: A
2012 study found that breast and colon cancer patients who exercised
regularly had half the recurrence rate compared to non-exercisers.21
Using Exercise as a Drug
Ideally, exercise would be used as a precise tool. I view it as a "drug"
that needs to be carefully prescribed to achieve maximum benefit. Too
little won't have a significant impact while too much could cause injury
and degenerate your health. If you have cancer, I would highly
recommend discussing exercise with your oncologist, and/or work with a
trained fitness professional to devise a safe and effective regimen.
Here are a few key considerations:
• Exercise efficiently: Avoid falling into the trap of exclusively focusing on the aerobic aspects of exercise, as this could actually prevent
optimal health. It's important to include a variety of techniques:
strength training, aerobics, core-building activities, and stretching.
Most important of all however, is to make sure you include high-intensity, burst-type exercise once or twice a week. High-intensity interval training (HIIT)
has been shown to be far more effective and efficient than other forms
of exercise, and virtually any exercise can be turned into a high
intensity routine, including walking (by speeding it up) and weight training (by slowing it down). • Find the right "dose:"
Researchers have suggested there's a dose-response relationship between
exercise and lowered risk of cancer, with more exercise producing
greater protection.22 The exact dosage needed for maximum cancer protection has remained elusive though.
Two large-scale studies that have helped shed some light on the situation looked for the"Goldilocks zone" in which exercise produces the greatest benefit for longevity
in general. (Considering cancer is a top killer, maximizing longevity
means you reduce your risk of all disease, including cancer.)
The greatest benefit was found among those who got between 150 and 450
minutes of moderate exercise per week. This lowered their risk of early
death by 31 and 39 percent respectively. Exercising more than 450
minutes per week did not provide any further increase in longevity. In
fact, exercising 25 hours a week or more only provided a 31 percent
mortality risk reduction.
The studies showed that incorporating more high-intensity exercises can
also boost longevity, compared to exercising at a consistently moderate
pace.
Keep in mind that as you increase the intensity, you need to decrease
the duration and frequency of your exercise. HIIT should only be done
once to three times a week, max. Any more will likely be
counterproductive, as your body needs time to recuperate from the
strain. On non-HIIT days, do other less strenuous activities. • The sooner you start the better, but it's never too late.
If you have kids, now's the time to put them on the track to health by
coaxing and encouraging them to be as active as possible. In one study,
women who exercised for just under 1.5 hours a week during their teenage
years (but not in adulthood) had a 16 percent lower risk of dying from
cancer in middle age.
They also had 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.23,24
That said, you're not doomed if you're now getting older and haven't
kept up your exercise routine. It's never too late to start, as the
biochemical changes produced by exercise will kick in no matter what
your age. • Engage in non-exercise movement daily: Consider walking more, in addition
to your regular workout regimen. A healthy goal is 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.
Exercise Improves Your Odds of a Long and Healthy Life
If you want to prevent disease, exercise! In light of the
evidence showing that exercise has a profound impact on health and the
prevention of disease such as cancer, it would be foolish in the extreme
to ignore such advice. Especially when you consider the staggering
failure rate of the conventional drug paradigm. Medical mistakes and
dangerous drugs are in fact the third leading cause of death in the U.S.
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
are also largely dependent on exercise. In fact, one of the primary
benefits of exercise is that it boosts your mitochondrial health, which
can play a decisive role 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. Daily non-exercise activity and movement is equally
important, as frequent and prolonged sitting has been shown to be as dangerous as smoking when it comes to cutting years off your lifespan.
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.
Also, if you have children, it would be wise to help them build a solid
foundation for good health by encouraging daily physical activity. In
many cases, that means devising ways to lure them away from electronic
games and gadgets. One great way to do that is to exercise as a family,
with focus on having fun together. Not only will everyone benefit from
the physical activity, but it'll help strengthen emotional bonds as
well.
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