Exercise has proven to be good at slightly different things from what was once thought. It may not be the magic bullet for weight loss people hoped it was, for instance, but it does seem to do other amazing things—like prompt the brain to grow new neurons and reduce the risk of serious and chronic health problems.
In recent years, in fact, a number of studies have found that the more one exercises (within reason), the lower his or her risk of multiple types of cancer. And a new study suggests that it really doesn’t have to be that much: just getting the recommended amount of weekly physical activity is linked to reduced risk of seven different types of cancer.
The research was published this week in the Journal of Clinical Oncology.
"Physical activity guidelines have largely been based on their impact on chronic diseases like cardiovascular disease and diabetes," said study author Alpa Patel in a statement. "These data provide strong support that these recommended levels are important to cancer prevention, as well."
The researchers, from a number of institutions around the world, including the National Cancer Institute, Karolinska Institutet, and the Harvard T.H. Chan School of Public Health, analyzed data from some 750,000 participants over a period of more than 10 years. The participants all reported on a number of variables, including the amount of physical activity they got in their leisure time. The researchers correlated this to the participants’ risk of developing cancer over the years.
Current recommendations call for 2.5 to 5 hours per week of moderate-intensity activity (like brisk walking) or 1.25 to 2.5 hours per week of vigorous activity; both amounts correspond to 7.5-15 metabolic equivalent task (MET) hours/week.
The team found that people who got in this range had a reduced risk for seven types of cancer: in men, but not women, a lower risk of colon cancer (8% for 7.5 MET hours/week and 14% for 15 MET hours/week); in women, lower risk of breast cancer (6%-10%), endometrial cancer (10%-18%), and non-Hodgkin lymphoma (11%-18%). Both sexes had reduced risk of kidney cancer (11%-17%), myeloma (14%-19%), and liver cancer (18%-27%).
People who got more exercise than the recommended levels had even lower risk of certain types of cancer (colon, breast, endometrial, and head and neck cancer), making the risk reduction dependent on exercise “dose.”
Another interesting finding had to do with the fact that the risk reduction was quite varied—for instance, for breast cancer there was a 6%-10% lower risk, but with liver cancer, there was a 18%-27% reduced risk. This, the researchers suggest, has to do with the different mechanisms behind cancer development: breast cancer has more to do with hormones and inflammation, while liver cancer may have to do with glucose and fatty acid metabolism—exercise might have a more direct relationship with the mechanisms behind liver cancer than breast cancer.
In 2016, the team had reported that more significant amounts of exercise was linked to a reduction in 13 types of cancer, but as they point out in the new study, the research on lower—i.e., recommended—amounts had been less clear. So it’s very good news that relatively doable amounts of exercise can significantly reduce the risk of multiple types of cancer.
“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 authors write. In other words, the current exercise guidelines are legit, and worth trying to incorporate those few hours of moderate or vigorous activity into the week.