Can Physical Activity Reduce the Risk of Breast Cancer?
Can physical activity reduce the risk of breast cancer? It’s an important question. It’s safe to say that society has accepted the body-mind-spirit connection, especially in times of stress and illness. Research is firmly behind the idea that one of the keys to all three is to take care of the first: the body. Scientists are now trying to determine specific ways that exercise improves the risks associated with cancer– before, during and after diagnosis.
Early first menses, late menopause, breast density, age at first childbirth, family history of the disease. There are so many risk factors for breast cancer that are completely out of our control. It feels like there’s nothing much that women can do to avoid initial diagnosis or recurrence of the disease. But physical activity is one thing we can control.
“There are things we can do each and every day to reduce the risk of breast cancer, to improve chances of not dying from breast cancer, and to decrease the risk of recurrence,” says Colleen Doyle, MS, RD, Director of Nutrition and Physical Activity at the American Cancer Society.
For years, oncologists, surgeons, and other healthcare professionals have told women during and after cancer treatment to take it easy, rest, relax. It turns out, though, that physical activity can reduce the risk of breast cancer.
Physical Activity and Breast Cancer: The Statistics
People who exercise are less likely to get breast cancer than those who are less physically active, says Jennifer Ligibel, MD, medical oncologist at Boston’s Dana Farber Cancer Institute. Specifically, women who are physically active on a regular basis are between 25 and 30 percent less likely to be diagnosed with breast cancer.
A study at the German Cancer Research Center (Deutsches Krebsforschungazentrum) in Heidelberg, led by Drs. Karen Steindorf and Jenny Chang-Claude, provides some useful findings. Specifically, the researchers found that 19.4 percent of invasive postmenopausal breast cancers are attributed to hormone replacement therapy and 12.8 percent to a lack of physical activity.
Another study, published in 2007 by Dr. Leslie Bernstein of the University of Southern California, also builds the case that physical activity can reduce the risk of breast cancer; it found that women who exercised strenuously for five hours a week lowered their risk of invasive breast cancer, particularly of estrogen receptor-negative invasive breast cancer, when compared with women who were less active.
The challenge with these studies (and most others that have been completed to date) is that they are observational; none are randomized, observes Ligibel. As a result, it is possible that women who are already doing better may be the ones reporting their results to the researchers.
“We cannot prove a causal relationship based on these studies,” says Ligibel, though there is clearly a relationship between physical activity and improved rates of survivorship.
But the accumulated data are meaningful. In fact, Doyle notes “the data are strong enough to call our recommendations ‘Guidelines’.” But it can make a big difference – and it is one of the few concrete steps that women can take to improve their health.
It’s significant that physical activity can reduce the risk of breast cancer, and of course it can also improve cardiovascular fitness, muscle strength, bone health and body composition and can play a role in weight loss.
When to Start and What to Do
“Today is the best time to start to exercise. There is no point at which exercise cannot help prevent breast cancer from starting in the first place, or from recurring,” says Ligibel.
In general, moderate exercise translates into a twenty-minute mile, says Ligibel, though the precise definition may vary from study to study. “These women are not marathoners,” she adds. “They spend three hours a week doing moderate walking.” That’s encouraging; exercise can help your life and prolong your life, but it needn’t completely take over your life. Asking “Can physical activity reduce the risk of breast cancer?” need not require you to be a super-athlete.
In fact, you can make a difference for yourself even through moderate physical activities. This includes a range of sports and daily activities, such as:
- ice and roller skating
- horseback riding
- downhill skiing
- brisk walking
- mowing the lawn
- raking and trimming shrubs
- doing housework
Great exercices you can do at home:
- workout with dumbbells
- activites with indoor home equipment
- freeweight excercises
And fitness isn’t limited to cardio exercise. Resistance training can be particularly helpful in improving bone health and density, muscle strength and flexibility. Studies show that weight training can decrease the incidence and severity of lymphedema, notes Doyle.
“Historically, women have been told to not do upper body weight training for fear of getting or worsening lymphedema,” says Doyle. But that is not the case. “Women do not have to be afraid of weight training.” In fact, according to the American Cancer Society, a number of studies have shown that this sort of physical activity is not only safe, but can actually reduce the incidence and severity of lymphedema.
Lower Risk of Breast Cancer by Maintaining the Ideal Weight
Obesity is also a concern. According to the American Cancer Society, there is a strong connection between being overweight or obese and an increased risk of many types of cancers, including breast cancer among postmenopausal women who don’t engage in physical activity.
Healthcare professionals determine a healthy weight for an individual by using the body mass index (BMI), which determines the ideal weight based on the person’s height. To check your own status, you can use the BMI calculator developed by the U.S Department of Health and Human Services’ National Institutes of Health.
One researcher, Lee Jones, Ph.D., Associate Professor at the Duke University Medical Center in Durham, NC, notes that most of the studies – the ones we’ve been talking about and others – are observational for a simple reason: It’s hard to conduct a controlled experiment with humans. We’re kind of difficult to control.
Jones, who has three appointments: Associate Professor of Radiation Oncology, Associate Professor of Pathology, and Associate Professor in Psychiatry and Behavioral Sciences, is conducting studies on mice to explore the relationship between exercise and tumor size. While the results are still preliminary, he has found that tumors grow 30 percent more slowly in female mice on an exercise routine than those that are sedentary.
The difficulty with studies in rats, says Ligibel, is that mice and people are different. People are more complex. As a result, it is difficult to generalize from studies in rats to behavior in human beings.
As a result, researchers have been trying to figure out what causes these improved outcomes in humans. “When people start to exercise,” says Ligibel, “the hormone levels that are linked to breast cancer change in a positive direction.” Specifically, insulin and estrogen levels decrease while levels of other hormones that are better when higher tend to increase.
Ligibel and colleagues at the Dana Farber Cancer Institute measured insulin and blood glucose levels in 101 women, along with their weight, body composition and circumference of waist and hips.
Half of the women performed a 16-week regimen of cardiovascular and strength training while the other half were left to their own devices. At the end of the experiment, the women who exercised had lowered their insulin measurements by an amount that approached statistical significance. In addition, the women who were more active reduced their hip circumference.
Another area that researchers are looking into is trying to determine the volume and type of exercise that is most effective in fighting cancer. “We want to be able to personalize exercise, just as we personalize chemotherapy” for the individual patient. In the meantime, Jones suggests women follow the American Cancer Society’s general recommendations on physical activity.
“It doesn’t matter what you do, you just need to get your heart rate up, sweat, and do at least ten to fifteen minutes of physical activity at a time.” –Jennifer Ligibel, MD
Set Realistic Physical Activity Goals and Lower Your Breast Cancer Risk
While exercise is important in decreasing cancer risk, you don’t want to run outside and start immediately with a ten-mile jog. Keep in mind any special considerations.
“Someone who’s not active at all should probably start with ten minutes of physical activity a few days a week,” says Ligibel. “It is important to set realistic goals and to work hard at meeting them.”
She recommends that you delay activity if you are anemic; wait until your iron levels rise. If you’re in radiation treatment, avoid chlorine as it might aggravate already sensitive skin.
If you have a catheter or port, avoid resistance training in that part of the body (say, the upper body). And if you are experiencing extreme fatigue, don’t push yourself.
Patients in active treatment should also be careful about where they exercise. Someone in chemotherapy who has a low white cell count should avoid public gyms and public pools. And someone who has had a bone marrow transplant should probably stay away from public places for about a year, says Doyle.
In addition, in people who are older who have bone disease or significant impairments such as arthritis or neuropathy, it is important to focus on balance. You don’t want to fall.
Can Physical Activity Reduce the Risk of Breast Cancer?: The Conclusion
It’s always best to consult your doctor before beginning any exercise program. But don’t doubt that physical activity can reduce the risk of breast cancer and of recurrence. Start as soon as you can.