The longer women can breastfeed, the more they are protected against breast cancer.

The importance of long-term breastfeeding is so great that the rate of breast cancer in the West would be more than halved if Western women had larger families and continued to breastfeed for longer periods.

The risk of breast cancer appears to be reduced by more than 4 per cent for every 12 months a woman breastfeeds, and by 7 per cent for every birth, a new study has discovered.

The overall rate of breast cancer would fall from 6.3 per 100 women by age 70 to just 2.7 if Western women emulated the birth rates and breastfeeding practices of women in other parts of the world, who tend to have more children and breastfeed for much longer.

Researchers studied the records of 50,302 women with breast cancer and compared them with 96,973 healthy controls. Women with breast cancer tended to have fewer births than those in the cancer-free group, fewer had breastfed at all and those that did had breastfed for shorter periods of time.

This risk did not alter between women in developed and developing countries, or between ethnic backgrounds, age or the age when the first child was born.

The research team, from the Collaborative Group on Hormonal Factors in Breast Cancer, studied 80 per cent of all studies into breastfeeding and breast cancer before arriving at these conclusions (Lancet, 2002; 360: 187-95).