Fiber and Breast Cancer Risk

by Stephanie Kramer

Fiber is considered one of the most important nutrients in our diet, and for good reason. It has been known for years that fiber helps with regular digestion and can protect against heart disease and colon cancer.1

A recent study from Harvard T.H. Chan School of Public Health shows that increasing fiber intake may also reduce the risk of getting breast cancer.2 The study focused on a group of 90,534 females from the Nurses Health Study II who filled out Food Frequency Questionnaires (FFQs) starting in 1991 and every four years after. In 1998, they also filled out a questionnaire about their diet in high school. Previous studies of fiber intake and breast cancer were insignificant, but none of them examined dietary intake during adolescence and young adulthood.

fiber - fruits and veggiesResults from this study showed that breast cancer risk was 12 – 19% lower among women who ate more dietary fiber in early adulthood. The greatest benefits seemed to be when the fiber was from fruits and vegetables; whether the fiber was soluble or insoluble did not seem to matter.

For each additional 10 g of fiber daily – about 1 apple or 1⁄2 cup cooked kidney beans – breast cancer risk dropped 13%!

The researchers suspect that fiber inhibits reabsorption of estrogen, therefore decreasing blood levels of the hormone. Since high estrogen levels are linked to the development of breast cancer, it makes sense that lowering blood levels of the hormone would decrease the risk of getting breast cancer.3

The most significant finding of this study was that increasing dietary fiber is especially important for adolescents and young adults; so if you are in that age group, it is even more important to get the proper amount of fiber and reduce your risk of disease later in life!

Struggling to get enough fiber in your diet? Check out these tips:4

  • Switch to higher fiber breads (with at least 4 g of fiber)high fiber bread
  • Ditch sugary breakfast cereals and replace with oats or a high fiber cereal
  • Snack on fruits and veggies instead of processed snacks
  • Make sure not to peel the skin off fruits and veggies, as it contains most of the insoluble fiber
  • Add flaxseeds to trail mix or flaxseed meal to yogurt and cereals
  • Snack on prunes when you have a sweet tooth (1 cup of prunes has 12 g of fiber!)
  • Add cooked beans to your salads, soups or just as a side dish

NOTE: Daily Fiber Recommendations:4 25 grams per day for women, 38 grams per day for men


  • Insoluble fiber: Adds bulk to the stool and helps food pass more quickly through
  • Soluble fiber: Slows down digestion by attracting water to itself and therefore helps with greater absorption of nutrients.


  1. Soluble vs. Insoluble Fiber: MedlinePlus Medical Encyclopedia.” U.S National Library of Medicine. U.S. National Library of Medicine, n.d. Web. 11 Feb. 2016.
  2. Maryam S, Farvid, A, Eliassen H, Cho E, Liao X, Chen WY, Willett WC. Dietary fiber intake in young adults and breast cancer risk. Pediatrics, 137(3):e20151226 DOI:10.1542/peds.2015-1226.
  3. Rose DP, Goldman M, Connolly JM, Strong LE. High-fiber diet reduces serum estrogen concentrations in premenopausal women. American Journal of Clinical Nutrition 1991; 54:520-5.
  4. Brown, Amy C. Understanding Food: Principles and Preparation. Belmont, CA: Thomson/Wadsworth, 2015.
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