This study, carried out by Cancer Research UK, showed that women who did 16-17 hours of housework per week cut their risk of breast cancer by 20% for postmenopausal women and 30% for premenopausal women. Further, it was housework specifically that has this beneficial effect, not other forms of physical activity;
Women who exercise by doing the housework can reduce their risk of breast cancer, a study suggests.
The research on more than 200,000 women from nine European countries found doing household chores was far more cancer protective than playing sport.
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Out of all of the activities, only housework significantly reduced the risk of both pre- and post-menopausal women getting the disease.
This study sounds fishy to me.