It’s well-known that exercise is good for your heart and can lower the risk of developing medical conditions like heart disease and diabetes. A large study released Monday now shows that exercise is an important factor in reducing the risk of developing a wide range of cancers, too.
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Researchers from the National Cancer Institute were interested in whether physical activity can reduce cancer risk in the same way it helps maintain heart heart. They also wanted to know whether associations might vary by body size or whether a person smoked.
Their findings: A higher level of leisure-time physical activity was associated with lower risk for 13 of 26 types of cancer and a 7 percent lower risk of developing any type of cancer.
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Lowered risk of disease
For the participants who were moderately to vigorously active, the researchers found:
Higher levels of physical activity, however, were associated with an increased risk of early-stage prostate cancer and skin cancer.
The researchers say that more exposure to the sun is the likely reason for the increase in skin cancer risk because physical activity often takes place outdoors. They also observed that the physical activity–melanoma association was stronger in geographic areas with higher levels of ultraviolet light.
The researchers theorize that physically active men are more likely to seek screening for prostate cancer, and so were more likely to be diagnosed with slow-growing, symptom-free disease.
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Leisure time activity
The researchers analyzed data from 1.4 million participants in 12 U.S. and European study groups who reported their physical activity between 1987 and 2004. The team also looked at the incidence of 26 kinds of cancer that occurred in the study follow-up period, which lasted 11 years on average.
The study focused on what the authors called leisure time activity, which they defined as physical activity done at an individual’s discretion to improve or maintain fitness or health. Some examples include walking, running and swimming. The participants reported how much time they spent on these activities each week. Walking 150 minutes per week, for example, was considered an average level of effort.
Even after researchers took body mass index into account, 10 of the associations between cancer risk and activity level remained. For lung cancer, the connection between lower risk and physical activity became even stronger after researchers factored in whether the participants smoked.
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Another way to avoid cancer
The study is important because it may indicate another strategy that people can use to cut their cancer risk, says oncologist Dale Shepard, MD, PhD.
Although scientists don’t know exactly why exercise impacts cancer risk, Dr. Shepard says it’s one of the keys to help prevent the disease.
“There are a lot of smaller studies that looked at just breast or just colon and we already know there’s some associations, but the strength of this study is that it shows 13 different cancers were impacted by people being more active,” Dr. Shepard says.
Dr. Shepard notes that for seven cancers — including kidney, lung and liver — the study shows a 20 percent or more reduction in cancer risk through higher levels of activity. For those of us trying to stay healthy, that is tremendously empowering information, he says.
“Eat a nutritious diet, get plenty of sleep, watch your weight and exercise. Those are things that prevent cancers,” Dr. Shepard says. “Those are things that if someone does get cancer, can help them get through their cancer treatments easier. So, exercise is an enormous component of this.”
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