Physical activity may lower risk of certain types of cancers

Getting the recommended amount of physical activity is linked to a reduced risk of seven types of cancer, researchers have found.

The study, published in the Journal of Clinical Oncology, analysed data from more than 750,000 adults in the United States, Europe and Australia and found that recommended amounts of physical activity correlated with lower risks of seven types of cancer.

"Physical activity guidelines have largely been based on their impact on chronic diseases like cardiovascular disease and diabetes," said Indian-origin researcher Alpa Patel from the American Cancer Society.

"These data provide strong support that these recommended levels are important to cancer prevention, as well,"

While it's long been known that physical activity is associated with a lower risk of several cancers, less clear has been the shape of the relationship and whether recommended amounts of physical activity are associated with lower risk.

Updated guidelines for activity 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.

Moderate-intensity activities are those that get you moving fast to burn off three to six times as much energy per minute as sitting quietly (three to six METs). Vigorous-intensity activities burn more than six METs.

MET (metabolic equivalent) is a term used to represent the intensity of exercise.

For the current analysis, 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.

They found engaging in recommended amounts of activity (7.5 to 15 MET hours/week) was associated with a statistically significant lower risk of seven of the 15 cancer types studied, with the reduction increasing with more MET hours.

Physical activity was associated with a lower risk of colon cancer in men (eight per cent for 7.5 MET hours/week; 14 per cent for 15 MET hours/week), female breast cancer (6 per cent-10 per cent), endometrial cancer (10 per cent -18 per cet), Kidney cancer (11 per cent-17 per cent), myeloma (14 per cent-19 per cent), liver cancer (18 per cent-27 per cent), and non-Hodgkin lymphoma (11 per cent-18 per cent in women).

The dose response was linear in shape for half of the associations and nonlinear for the others, the study said.

"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," said the study researchers from American Cancer Society in the US.