Researchers found regular moderate physical activity such as housework provides a better protection against breast cancer than more strenuous but less frequent sporting activity.

Doing housework was linked with a 29 percent reduction of breast cancer risk in pre-menopausal women compared with being inactive in the home. In post-menopausal women, the reduction was 19 percent.

Previous studies have found protective effect of being physically active against breast cancer in post-menopausal women.

The current study, published in the January edition of the journal Cancer Epidemiology Biomarkers and Prevention, is one of the first to examine the effect in pre-menopausal women.

In the current study, researchers analyzed data on three activities, work, leisure and housework among 218,169 women aged 20 to 80 from nine European countries.

On average, pre-menopausal women spent 17.7 hours each week doing housework while post-menopausal women spent 16.1.

The women were followed up for an average of 6.4 years during which 3,423 were diagnosed with breast cancer.

When all types of activity were combined, there was no association between physical activity and breast cancer risk.

But when physical activities were considered separately, researchers found women who did the most housework were significantly less likely to develop breast cancer.

And they found work and recreation activity were not as effective in reducing the risk of breast cancer.

"Increased non-occupational physical activity and, in particular, increased household activity, were significantly associated with reduced breast cancer risk, independent of other potential risk factors,” Dr Petra Lahmann of the Medical Research Council's Human Nutrition Research unit in Cambridge  was quoted by Telegram.co.uk as saying.

"Our results . . . provide additional evidence that moderate forms of physical activity, such as household activity, may be more important than less frequent but more intense recreational physical activity in reducing breast cancer risk."

A scientist affiliated with foodconsumer.org cautioned that the study did not reveal a causal relation between housework and breast cancer risk.  Although being active is good for overall health, but it is unclear whether being physically active is an independent factor for the reduction of breast cancer.

An estimated 230,000 women in the US and 44,000 in the UK each year are diagnosed with breast cancer. In the U.S., 15 percent of women will eventually get breast cancer.