Diets High in Soluble Fiber Shown to Reduce Breast Cancer Risk

by | Feb 20, 2012 | 2012, Breast Cancer, Cancer, Fiber

Written by Jessica Patella, ND.  A research summary with approximately half a million participants showed that diets with at least 25 grams per day in soluble fiber had a reduced risk of breast cancer. 

Breast cancer is the most common cancer in women and is the leading cause of cancer death among women in the United States (1). In 2008, 1.4 million new cases of breast cancer were diagnosed worldwide. Although breast cancer has typically been seen in industrialized, higher socio-economic countries, it is now being seen in middle and lower socio-economic countries as well (1-3).

Dietary factors, particularly dietary fiber, have long been suspected to play a role in the development of breast cancer.  This was based on observations that vegetarian women have lower levels of estrogen compared to omnivorous women (2,5).  A recent meta-analysis discovered an inverse relationship between dietary fiber intake and breast cancer risk (2). This was the first meta-analysis to explore this association.

A meta-analysis includes multiple research studies, in order to get a larger sample of results. The breast cancer and fiber meta-analysis included 17 publications with approximately half a million participants. After reviewing all the studies and analyzing the results based on dietary fiber intakes of fruit fiber, vegetable fiber, cereal fiber, soluble fiber and insoluble fiber, it was discovered the higher the intake of dietary fiber, the lower the risk for breast cancer (2).

The most pronounced results were seen with intakes of fiber of at least 25 grams per day compared to lower intakes (less than 25 grams per day). The association was only significant in the soluble fiber group. It was not significant for the insoluble fiber, fruit fiber, vegetable fiber or cereal fiber groups (2).

Soluble fiber attracts water in the gastrointestinal tract and slows down digestion. Sources of soluble fiber include: oatmeal, lentils, apples, oranges, pears, oat bran, strawberries, nuts, flaxseeds, beans, blueberries, psyllium, cucumbers, celery and carrots. In contrast, insoluble fiber adds bulk to the diet and tends to have a laxative effect. It is mainly found in whole grains and vegetables (6).

Three possible explanations for this finding include research showing that modified citrus pectin (a soluble fiber) reduces breast tumor growth and metastasis in mice (7). Soluble fiber also binds to estrogens; therefore, eliminating estrogens in the stool vs.being reabsorbed into the body (8). And high fiber intake reduces the risk of obesity or being overweight, which are risk factors for breast cancer (9).

In conclusion, diets high in soluble fiber show a reduced risk of breast cancer (2). Further studies exploring the mechanism behind the finding still need to be conducted.

Source: Aune, Dagfinn, et al. “Dietary fiber, whole grains, and risk of colorectal cancer: systematic review and dose-response meta-analysis of prospective studies.” Bmj 343 (2011): d6617.

© Open Access article under Creative Commons Attribution License for non-commercial use.

Click here to read the full text study.

Posted February 20, 2012.

References:

  1. Breast Cancer Statistics.  CDC.
  2. Aune D, et al. Dietary fiber and breast cancer: a systemic review and meta-analysis of prospective studies. 2012.  Annals of Oncology.  Doi:10.1093/annonc/mdr589.
  3. Ferlay J, Shin HR, Bray F et al. Estimates of worldwide burden of cancer in 2008: GLOBOCAN 2008. Int J Cancer 2010; 127: 2893–2917.
  4. Chia KS, et al. Profound changes in breast cancer incidence may reflect changes into a Westernized lifestyle: a comparative population-based study in Singapore and Sweden. Int J Cancer 2005; 113: 302–306.
  5. Goldin BR, Adlercreutz H, Gorbach SL et al. Estrogen excretion patterns and plasma levels in vegetarian and omnivorous women. N Engl J Med 1982; 307: 1542–1547.
  6. Dietary Fiber: Insoluble vs Soluble.  Web MD.
  7. Nangia-Makker P, et al. Inhibition of human cancer cell growth and metastasis in nude mice by oral intake of modified citrus pectin. J Natl Cancer Inst 2002; 94: 1854–1862.
  8. Cohen LA, et al. Wheat bran and psyllium diets: effects on N-methylnitrosourea-induced mammary tumorigenesis in F344 rats. J Natl Cancer Inst 1996; 88: 899–907.
  9. Liu S, et al. Relation between changes in intakes of dietary fiber and grain products and changes in weight and development of obesity among middle-aged women. Am J Clin Nutr 2003; 78: 920–927.