Physical Activity and Cancer Risk
A major new scientific report, that is set to help shape US government guidelines, has concluded there is strong evidence that physical activity lowers the risk of certain cancers in adults.
The 2018 Physical Activity Guidelines Advisory Committee Scientific Report also found, for the first time, that sedentary behavior is associated to increased risk of cancer.
Physical activity, along with keeping a healthy weight and eating well, can prevent close to one third of the most common cancer cases in the USA, according to AICR (American Institute for Cancer Research). This estimate of the US cancer cases that can be prevented, increases to nearly half when there is no smoking and no excessive exposure to the sun.
Anne McTiernan, AICR/WCRF Expert Panel Member and also a member of the 2018 Physical Activity Guidelines Advisory Committee, says, “We have strong evidence that being physically active decreases the risk for many cancers. While the greatest benefit was observed in people who are highly active, there was seen protection against cancer at all levels of activity.”
McTiernan advises, “You don’t need to become an athlete or spend a lot of money in order to gain the benefits of physical activity. All it takes is a pair of walking shoes and the determination to fit physical activity into your life.”
AICR research shows that maintaining a healthy weight is important for cancer prevention. Being overweight and obese is a cause of 11 cancers, including colon, postmenopausal breast, and endometrial.
Spending more time sitting is related to greater incidence of certain cancers, as well as to type 2 diabetes and other chronic diseases.
Evidence links type 2 diabetes with increased risk of several cancers.
There are several possible ways in which physical activity may act to lower cancer risk and, as the report points out, this is a critical area of research. Regular activity can help regulate body levels of insulin and other hormones that increase cancer risk at high levels. Being active may also decrease chronic inflammation. AICR recommends at least 30 minutes of moderate intensity physical activity daily for lower cancer risk.
This research confirms earlier research by an international team led by Dr. Steven C. Moore at NIH’s National Cancer Institute (NCI), which examined the associations between physical activity and various cancers. Results were published online on May 16, 2016, in JAMA Internal Medicine.
The researchers pooled data from 12 studies that together followed a total of 1.44 million people over time. Study participants were 19 to 98 years old (average age 59 years old), from the United States and Europe (with 57% female with no history of cancer). The studies assessed physical activity by using surveys that asked about time spent in moderate to vigorous leisure-time physical activities, such as walking, running, or swimming.
They then compared cancer risks for the groups with the highest (top 10%) and lowest (bottom 10%) levels of activity. The median level of activity was about 150 minutes of moderate-intensity activity per week. This is comparable to the minimum level of physical activity that experts recommend.
Participants were followed for a median of 11 years. During this time, 187,000 new cases of cancer arose. Cancer types were selected for analysis if there were at least 300 cases.
The researchers found that people with the highest level of leisure-time physical activity had a reduced risk for 13 of 26 types of cancer compared to those with the lowest level of activity. People with the highest activity had a 20% lower risk for 7 cancer types: esophageal adenocarcinoma, liver, lung, kidney, gastric cardia, endometrial, and myeloid leukemia. They also had a 10-20% lower risk for myeloma and cancers of the head and neck, rectum, bladder, and breast.
Every year, around 9 million people die of cancer worldwide and in the next 10 years cancer deaths are expected to increase to over 14 million per year.
According to the new data, nearly 50% of the most common cancers can be prevented by keeping a healthy weight , being physically active, adopting a healthy diet, saying NO to smoking and protecting ourselves from excessive exposure to the sun.