Previous studies have shown that breast cancer survivors who meet the current exercise recommendations, which is 2.5 hours of moderate intensity physical activity per week, are at 25 percent lower risk for dying from breast cancer.
However, new research from the US Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab), suggests that exceeding the recommendations may provide greater protection, and that running may be better than walking.
The study, by Berkeley Lab's Paul Williams of the lab's Life Sciences Division, followed 986 breast cancer survivors as part of the National Runners' and Walkers' Health Study.
Thirty-three of the 714 walkers and 13 of the 272 runners died from breast cancer over 9 years.
When analyzed together, their risk for breast cancer mortality decreased an average of 24 percent per metabolic equivalent (MET) hours per day of exercise, where one MET hour equals a little less than a mile of brisk walking or about two-thirds of a mile of running.
When the runners and walkers were looked at separately, there was significantly less mortality in those who ran than walked.
The runners' risk for breast cancer mortality decreased over 40 percent per MET hour per day.
Runners that averaged over 2 and a quarter miles per day were at 95 percent lower risk for breast cancer mortality than those that did not meet the current exercise recommendations.
In contrast, the walkers' risk for breast cancer mortality decreased a non-significant 5 percent per MET hour per day.
The study is published in the International Journal of Cancer.