Can breastfeeding protect you from breast cancer?

Experts agree that breast is best for your baby - but there's new evidence that it might benefit you too, by reducing the risk of breast cancer

Does breastfeeding protect you from breast cancer?

Experts agree that breastfeeding certainly does not increase the risk of developing breast cancer, and long-term breastfeeding may even reduce it.

'A number of studies, though not all, suggest a possible link between breastfeeding and a reduction in the risk of breast cancer,' according to Jackie Graveney, Director of Communications at Breakthrough Breast Cancer, 'However, there are many factors involved in whether a woman decides to breastfeed or not. Women should know as much as possible about breastfeeding so that they can make an informed decision.'

Results of studies have varied wildly. Two reports, published in 1999 and 1997, showed that pre-menopausal women had a 50 per cent lower risk of breast cancer if they had breastfed. Other studies show no conclusive link between breastfeeding and reduced risk of breast cancer.

Does the length of time you breastfeed make any difference?

The evidence for risk reduction becomes more consistent the longer women breastfeed. But, for it to make a significant difference, research suggests that a woman needs to breastfeed for a considerable length of time.

In one study, Chinese women who had breastfed for a total of six years or more over the course of their lives were found to have a 63% decrease in breast cancer incidence, compared to women who had never breastfed.

Further evidence comes from a Yale University study of US women, published in June 2001, which found that women who breastfeed their first child for more than 13 months have a slightly reduced risk of breast cancer.

How does breastfeeding protect you from breast cancer?

There are several theories. One is that breastfeeding reduces exposure to the female hormone oestrogen, which in turn reduces the risk of breast cancer.

Breastfeeding itself causes hormonal changes and delays the onset of ovulation after pregnancy, again reducing a woman's lifetime oestrogen exposure.

Another theory is that fat-soluble carcinogens and pollutants are not stored as efficiently in lactating breasts.

There is also some evidence that breastfeeding causes physical changes in breast cells that may make them more resistant to the mutations that can lead to cancer.