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Breastfeeding protects against cancer

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    Published online 19 July 2002 | Nature | doi:10.1038/news020715-13 News Breastfeeding protects against cancer Lack of breastfeeding major contributor to
    Message 1 of 1 , Jan 14, 2011

      Published online 19 July 2002 | Nature | doi:10.1038/news020715-13

      News

      Breastfeeding protects against cancer

      Lack of breastfeeding major contributor to Western breast cancer.

      Helen Pearson


      For every year a woman breastfeeds, her risk of breast cancer falls by more than four percent.© GettyImages

      Breastfeeding protects women from breast cancer, says a major new study. But researchers are reluctant to advise women to change their behaviour.

      1 in 8 women in the United States will develop breast cancer; 1 in 9 in Britain. The new study suggests that, for every year a woman breastfeeds, her risk of breast cancer falls by more than 4%. This is on top of the 7% reduction for each child she bears, and regardless of other risk factors such as genes, smoking or age of having her first child.

      Some 5% of breast cancers in the Western world - that's 25,000 per year - could be prevented if women who had two or three children breastfed each one for 6 months longer, the researchers calculate1.

      The results are "something else to factor in when trying to decide whether to breastfeed", says team member Gillian Reeves of the University of Oxford, UK. Telling women to change the number of children they bear or the length of time they spend breastfeeding is "unrealistic", she says.

      Governments and workplaces could do more to encourage breastfeeding, says cancer epidemiologist Tongzhang Zheng of Yale University in New Haven, Connecticut. "It's not supported - especially long-term breastfeeding," he says. In the United States, half of women do not breastfeed at all, compared with a quarter in Britain.

      The researchers now hope to discover what happens in the breast tissue during milk production that renders it more resistant to disease. If they can develop drugs that mimic this effect, it "may make big differences for a large number of people", says Helene Hayman, who chairs Cancer Research UK the charity that partly funded the study.

      Bigger is better

      An international research consortium called the Collaborative Group on Hormonal Factors in Breast Cancer pooled the results of 47 published studies in 30 countries involving more than 50,000 women with breast cancer and nearly 100,000 without.

      “Governments and workplaces could do more to encourage breast feeding”

      Tongzhang Zheng
      Yale University

      Of the women in the study, those in developed countries such as Britain and the United States had an average of two or three children and typically breastfed each for 2 to 3 months. Those in developing countries, where breast-cancer rates are four times lower, had six or seven children and breastfed for around 2 years each.

      "If women had the same number of children as those in developing countries and breastfed for as long, breast cancer would be a very rare disease," says lead researcher Valerie Beral, also of the University of Oxford.

      Breast-cancer incidence has begun to climb in developing countries, coincident with a fall in family size and duration of breastfeeding. In China, for example, restricting families to one child has been accompanied by such a rise. 

      Yale University

      • References
        1. Collaborative Group on Hormonal Factors in Breast Cancer, Breast Cancer and breastfeeding: collaborative reanalysis of individual data from 47 epidemiological studies in 30 countries, including 50,302 women with breast cancer and 96,973 women without the disease. Lancet 360, 187 - 196 (2002).


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