Brisk walking and other physical activities for 2.5-5 hours every week reduces risk of 7 types of cancer
Engaging in recommended amounts of leisure-time physical activity was associated with a significantly lower risk for breast, colon (men only), endometrial, kidney, myeloma, liver cancer and non-Hodgkin lymphoma (women only).
Doing some kind of physical activity for 2.5 to 5 hours every week — such as a moderately-intense activity like brisk walking — can significantly lower the risk of seven types of cancer.
This includes colon cancer in men, female breast cancer, endometrial cancer, kidney cancer, myeloma, liver cancer and non-Hodgkin lymphoma in women, according to an analysis by researchers from the National Cancer Institute, the American Cancer Society, and Harvard TH Chan School of Public Health. The benefits range from a 6% to 10% lower risk for breast cancer to an 18% to 27% lower risk for liver cancer.
"Physical activity guidelines have largely been based on their impact on chronic diseases like cardiovascular disease and diabetes. These data provide strong support that these recommended levels are important to cancer prevention, as well," says Dr Alpa Patel, senior scientific director of epidemiology research at the American Cancer Society, in the analysis.
In the US, 1.7 million individuals are diagnosed with invasive cancer and more than 600,000 people die as a result of malignant diseases every year.
While it is known that physical activity is associated with a lower risk of some types of cancer such as colon cancer, it is not clear whether the recommended amounts of physical activity are linked with reduced risk. Updated guidelines for activity in the US now state that people should aim for 2.5 to 5 hours/week of moderate-intensity activity or 1.25 to 2.5 hours/week of vigorous activity.
The researchers explain that moderate-intensity activities are those that get you moving fast enough or strenuously enough to burn off three to six times as much energy per minute as sitting quietly — that is, three to six metabolic equivalent tasks or METs. Vigorous-intensity activities burn more than six METs.
“An understanding of the amount and intensity of physical activity associated with reduced risk is essential for the application of evidence-based recommendations for cancer prevention,” says the study.
Accordingly, for the current study, the researchers examined whether the recommended amounts of physical activity — 2.5-5 hours/week of moderate-intensity activity or 7.5-15 metabolic equivalent task hours every week — are associated with lower risk.
The researchers included leisure-time physical activity. “Leisure-time physical activities encompass discretionary exercise, sports, and recreational pursuits, typically of a moderate to vigorous intensity, and done to maintain fitness or health,” says the study published in the Journal of Clinical Oncology.
A total of 755,459 participants (median age, 62 years) were followed for 10.1 years. The participants had no history of cancer at the start of follow-up. The investigators pooled data from nine prospective cohorts with self-reported leisure-time physical activity and follow-up for cancer incidence, looking at the relationship between physical activity with incidence of 15 types of cancer.
The analysis shows that engagement in recommended amounts of activity (7.5-15 MET-hours/week) was associated with a statistically significant lower risk of 7 of the 15 cancer types studied. More activity was linked to lower risk for several cancer types.
“Engagement in recommended amounts of leisure-time physical activity (7.5-15 MET-hours/week, an equivalent of 2.5 to 5.0 hours/week of moderate-intensity activity) was associated with a statistically significant lower risk of 7 of the 15 cancer types studied. This includes colon (8%-14% lower risk in men), breast (6%-10% lower risk), endometrial (10%-18% lower risk), kidney (11%-17% lower risk), myeloma (14%-19% lower risk), liver (18%-27% lower risk), and non-Hodgkin lymphoma (11%-18% lower risk in women). Both moderate and vigorous-intensity activity seemed to be associated with lower risk for colon, breast, and kidney cancer,” say the researchers in their findings.
They say: "These findings provide direct quantitative support for the levels of activity recommended for cancer prevention and provide actionable evidence for ongoing and future cancer prevention efforts."
The team recommends that healthcare providers, fitness professionals, and public health practitioners should encourage adults to adopt and maintain physical activity at recommended levels to lower risks of multiple cancers.