Walking appears to reduce the risk of breast cancer in postmenopausal women, a new study has found.

US scientists looked at whether recreational physical activity - specifically walking - reduced the risk of breast cancer in over 73,000 postmenopausal women. All were aged between 50 and 74.

The participants provided information on the types of exercise they did and for how long. They also provided information on leisure time activities such as reading and watching television.

The participants were monitored over a 12-year period and during this time, more than 4,700 developed breast cancer.

The study found that women who undertook at least one hour of vigorous physical activity every day had a 25% reduced risk of developing breast cancer compared to women who were the least active.

However among women who admitted that walking was their only physical activity, those who walked at least seven hours per week had a 14% reduced risk of developing breast cancer compared to those who walked for less than three hours per week.

"Given that many women report some daily walking, promoting walking as a healthy leisure-time activity could be an effective strategy for increasing physical activity among postmenopausal women. We were pleased to find that without any other recreational activity, just walking an average of one hour per day was associated with lower risk of breast cancer in these women," the scientists from the American Cancer Society in Atlanta said.

They added that they found no link between the risk of breast cancer and the amount of time spent sitting.

Details of these findings are published in the journal, Cancer Epidemiology, Biomarkers & Prevention.