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:
- 20 to 30 percent lower risk of breast cancer2
- 38 percent reduced risk of invasive breast cancers3
- 30 to 40 percent lower risk of colon cancer4
- 44 percent lower risk of bowel cancer after the age of 655
- 55 percent lower risk of lung cancer6
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.
✓ 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.