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Breastfeeding Longer Seems to Help Protect Against Breast Cancer

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We know that breastfeeding can lower breast cancer risk, especially if you breastfeed for longer than 1 year. This is because:

  • making milk limits breast cells’ ability to act abnormally
  • most women have fewer menstrual cycles when they’re breastfeeding, which means lower estrogen levels
  • many women tend to eat more nutritious food and make healthier lifestyle choices (avoiding alcohol and not smoking) while they’re breastfeeding

A new study adds more evidence to the benefits of breastfeeding for breast health. Researchers found that non-smoking women who breastfed for more than 6 months tended to be diagnosed with breast cancer later in life compared to non-smoking women who breastfed for shorter periods of time or not at all.

The study was published online on Aug. 13, 2013 by the Journal of Clinical Nursing.

Read the abstract of “Breastfeeding and the prevention of breast cancer: a retrospective review of clinical histories.”

This study was a retrospective study, which means the researchers analyzed information that was collected before the study was designed. Some doctors think that the results of retrospective studies aren’t as strong as studies that are designed first and then collect new information specifically for that study.

The researchers looked at the medical records of 504 women in Granada, Spain who were diagnosed with breast cancer when they were between 19 and 91 years old. All the women were diagnosed at one clinic between 2004 and 2009.

The average age at breast cancer diagnosis was:

  • 56.7 in the 364 women who hadn’t had children or breastfed for fewer than 3 months
  • 55.5 in the 109 women who breastfed for 3 to 6 months
  • 65.4 in the 31 women who breastfed for more than 6 months

When the researchers compared women who smoked to women who didn’t smoke, they found that smoking affected breast cancer risk more than breastfeeding. Breastfeeding for longer than 6 months only seemed to offer protection to women who didn’t smoke:

  • women who didn’t breastfeed or breastfed fewer than 3 months and smoked were about 7 years younger when diagnosed than similar women who didn’t smoke
  • women who breastfed for 3 to 6 months and smoked were about 11 years younger when diagnosed than similar women who didn’t smoke
  • women who breastfed for more than 6 months and smoked were about 21 years younger when diagnosed than similar women who didn’t smoke

While the results of this study seem to confirm the benefits of breastfeeding and the dangers of smoking on breast health, doctors do have some concerns about the study:

  • The study was small and all the women were diagnosed at the same clinic. It’s not clear if the findings would apply to a larger, more diverse group of women.
  • The researchers didn’t ask the women who breastfed if that was the only food their child was getting. Women who smoke may have trouble making enough milk and may have to supplement their child’s food with bottles. This could affect how long smokers are able to breastfeed.

The decision to breastfeed is very personal and depends on your unique situation.

If breastfeeding is an option for you, you may want to consider it. Besides possibly lowering your breast cancer risk, breastfeeding gives your child antibodies through the breast milk that can protect him/her from bacterial and viral infections. Still, these are highly individual decisions affected by many factors besides breast cancer risk and whether you are able to breast feed.

Breastfeeding can be a challenge after a breast cancer diagnosis. After a double mastectomy, sadly, breastfeeding is impossible. After lumpectomy and radiation, the treated breast usually produces little or no milk, but the other breast usually can make milk normally. The milk from one breast may be enough or you may have to supplement with formula. Some women may choose to use a breast milk donor. An experienced breastfeeding coach can help you figure out the best possible solution for your unique situation.

Whether or not you breastfeed, there are lifestyle choices you can make to keep your breast cancer risk as low as it can be:

  • never smoking (or quitting if you do smoke)
  • maintaining a healthy weight
  • exercising regularly
  • limiting alcohol
  • eating nutritious food

For more information on steps you can take to reduce breast cancer risk, visit the Lower Your Risk section.

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