By Dr. Mercola
Many people view exercise as a tool for weight loss, muscle building, and improving cardiovascular health, but it does much more than that. Exercise is like a whole-body health tonic, impacting you down to the cellular level.
It reduces your risk of many different chronic diseases, including the second leading cause of death in the US – cancer. There are a number of reasons why exercise is an effective anti-cancer tool.
For starters, exercise drives your insulin levels down, and controlling insulin levels is one of the most powerful ways to reduce your cancer risk. It's also been suggested that apoptosis (programmed cell death) is triggered by exercise, causing cancer cells to die.
Exercise also improves the circulation of immune cells in your blood. The job of these cells is to neutralize pathogens throughout your body, as well as destroy precancerous cells before they become cancerous.
The better these cells circulate, the more efficient your immune system is at defending itself against infections and diseases like cancer.
Further, a study published in the British Medical Journal noted that hundreds of studies link physical activity to cancer risk, and revealed several biological functions that may directly influence this risk.1 These effects include changes in:
Cardiovascular capacity Energy balance Pulmonary capacity Immune function Bowel motility Antioxidant defense Hormone levels DNA repair
Five Hours of Exercise a Week Lowers Your Breast Cancer Risk
In previously inactive post-menopausal women, a one-year “prescription” to exercise moderately to vigorously for 300 minutes a week leads to greater reductions in body fat than exercising for 150 minutes a week.2
Obesity exposes women to higher estrogen levels because estrogen is both produced and stored in fat tissue. Women carrying excess body fat therefore have more estrogen and leptin, which can lead to insulin resistance and the development of more fat tissue.
This produces even more estrogen — it’s a vicious cycle that may raise the risk of estrogen-sensitive cancers such as breast cancer. Reducing body fat, and with it estrogen levels, is one more way that physical activity may lower cancer risk. The researchers noted:3
“A possible association between physical activity and post-menopausal breast cancer risk is supported by more than 100 epidemiologic studies, with strong biologic rationale supporting fat loss as an important (though not the only) mediator of this association.
…Our findings of a dose-response effect of exercise on total fat mass and several other adiposity measures, including abdominal fat, especially in obese women, provide a basis for encouraging post-menopausal women to exercise at least 300 minutes/week, longer than the minimum recommended for cancer prevention.”
Past Research Suggests Exercise Might Reduce Risk of Breast Cancer by 30 to 40 Percent
The new study is only the latest showing regular physical activity drives down your cancer risk. In a review of published epidemiologic studies on physical activity and the risk of developing cancer, it's noted:4
"With regard to breast cancer, there is reasonably clear evidence that physically active women have about a 20-30% reduction in risk, compared with inactive women.
It also appears that 30-60 min [a day] 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."
Two other studies echoed this finding:
- 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 cancer5
- Strenuous activity in teens and moderate activity after menopause also lead to a reduction in breast cancer risk6
- A systematic review of seven cohort studies and 14 case-control studies also found that physical activity reduces the risk of breast cancer, particularly in post-menopausal women7
What Other Types of Cancer Does Exercise Benefit?
It’s not only breast cancer that’s prevented by exercise. According to the National Cancer Institute:8
“There is convincing evidence that physical activity is associated with a reduced risk of cancers of the colon and breast. Several studies also have reported links between physical activity and a reduced risk of cancers of the prostate, lung, and lining of the uterus (endometrial cancer).”
One study revealed that physically active men and women have about a 30-40 percent reduction in the risk of developing colon cancer compared with inactive persons, for instance.9 Physical activity also appears to lower the risk of pancreatic cancer by about 11 percent.10
Previous animal research suggests regular exercise may be the key to significantly reduce your chances of developing liver cancer, which is among the most common types of cancer.11
More recently, research published in the journal JAMA Oncology found that being fit in middle age cut men’s risk of being diagnosed with lung cancer by 55 percent and lowered the risk of bowel cancer by 44 percent.12
And yet another study revealed that men who regularly worked out with weights and had the highest muscle strength were between 30 percent and 40 percent less likely to die from cancer.13
Equally impressive were the results from a Finnish study, which found men who exercised intensely for 30 minutes a day had a 50 percent lower risk of dying prematurely from cancer.14 Taken together, the research speaks loud and clear that staying active is a key element to avoiding cancer throughout your lifetime.
Exercise Should Be a Standard of Care for Cancer Patients
Exercise can not only help slash your risk of cancer, it also helps cancer patients recuperate faster and diminishes your risk of cancer recurrence. A report issued by the British organization Macmillan Cancer Support in 2012 argued that exercise really should be part of standard cancer care.15
It recommended that all patients getting cancer treatment should be told to engage in moderate-intensity exercise for two and a half hours every week, stating that the advice to rest and take it easy after treatment is an outdated view. According to Ciaran Devane, chief executive of Macmillan Cancer Support:
"Cancer patients would be shocked if they knew just how much of a benefit physical activity could have on their recovery and long term health, in some cases reducing their chances of having to go through the grueling ordeal of treatment all over again..."
For example, previous research has shown that breast and colon cancer patients who exercise regularly have half the recurrence rate than non-exercisers. High levels of cardiorespiratory fitness (CRF) in middle age also helped men survive cancer, reducing their risk of dying from lung, bowel, and prostate cancer by nearly one-third (32 percent).16 Macmillan Cancer Support also notes that exercise can help you to mitigate some of the common side effects of conventional cancer treatment, including:
Reduce fatigue and improve your energy levels Manage stress, anxiety, low mood, or depression Improve bone health Improve heart health (some chemotherapy drugs and radiotherapy can cause heart problems later in life) Build muscle strength, relieve pain, and improve range of movement Maintain a healthy weight Sleep better Improve your appetite
High-Intensity Interval Training (HIIT) for Cancer Prevention?
Myokines — a class of cell-signaling proteins produced by muscle fibers — can combat cancer and metabolic syndrome. High-intensity training effectively stimulates your muscles to release anti-inflammatory myokines, which in turn increase your insulin sensitivity and glucose use inside your muscles. They also increase liberation of fat from adipose cells and the burning of the fat within the skeletal muscle.
Acting as chemical messengers, these myokines inhibit the release and the effect of the inflammatory cytokines produced by body fat, which are known to be elevated in people who develop cancer. They also significantly reduce body fat irrespective of calorie intake. Dr. Doug McGuff, an expert on the importance of high-intensity interval training (HIIT), explains:
"In my book, Body By Science, my co-author and I decided to define health in our own terms. One of the best ways I could describe it is that there's an appropriate balance between the catabolic (breakdown) and anabolic (build-up) state. There has to be a balance in the body. That's what this interplay between anti-inflammatory myokines produced by muscle and inflammatory cytokines produced by body fat and other tissues comes into play. There is a critical balance there that's important.
When that balance gets disrupted by changes in lifestyle that are not congruent with our evolutionary background, that's when disease starts to happen.”
Unfortunately, anywhere from 90 to 98 percent of people who exercise are NOT doing high-intensity exercises. By focusing on slow endurance-type exercises, such as running on a treadmill, you actually forgo many of the most profound benefits that exercise has to offer. You can find all the details on how to perform HIIT, including a sample HIIT workout, here.
Even if You Exercise, Sitting Too Much Will Raise Your Cancer Risk
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. Ideally, aim for 7,000 to 10,000 steps per day. Also avoid sitting as much as possible — ideally limiting your sitting to three hours a day or less.
There’s really compelling evidence showing that when you sit for excessive lengths of time, disease processes set in that independently raise your mortality risk, even if you eat right, exercise regularly and are very fit. For example, one study presented at the 2015 Inaugural Active Working Summit found that sitting increases:17
- Lung cancer by 54 percent
- Uterine cancer by 66 percent
- Colon cancer by 30 percent
The reason for this increased cancer risk is thought to be linked to weight gain and associated biochemical changes, such as alterations in hormones, metabolic dysfunction, leptin dysfunction, and inflammation — all of which promote cancer. Naturally, if you have cancer or any other chronic disease, you will need to tailor your exercise routine and sitting habits to your individual circumstances, taking into account your fitness level and current health.
But often you will be able to take part in a regular exercise program – one that involves a variety of exercises like strength training, core-building, stretching, aerobic, and anaerobic – with very little changes necessary. However, at times you may find you need to exercise at a lower intensity or for shorter durations. Always listen to your body and if you feel you need a break, take time to rest. But even exercising for just a few minutes a day is better than not exercising at all, and you'll likely find that your stamina increases and you're able 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 cancer. And remember also that exercise is just one part of a comprehensive cancer-prevention program. You’ll also want to pay attention to your stress levels, sleep quality, toxic exposures, and, of course, your diet – the latter of which is among the most important factors of all.