Caffeine Consumption Shown Not To Increase Overall Breast Cancer Risk

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Main Category: Breast Cancer
Also Included In: Cancer / Oncology;  Women's Health / Gynecology
Article Date: 15 Oct 2008 - 0:00 PDT

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A woman's risk of breast cancer is not increased by consuming caffeine, concludes a report published in the October 13 issue of Archives of Internal Medicine. The report, however, also found that caffeine and coffee consumption is slightly linked to breast cancer in women with benign breast disease.

Contained in coffee, tea, chocolate, and some medications, caffeine is most likely the most frequently consumed drug in the world. A relationship between caffeine and breast complications was established when women with non-cancerous breast disease removed caffeine from their diets and were subsequently relieved from their symptoms. That finding led researchers to hypothesize that caffeine may increase the risk of breast cancer.

Ken Ishitani, M.D., Ph.D. (Brigham and Women's Hospital and Harvard Medical School, Boston, and Tokyo Women's Medical University, Japan) and colleagues analyzed a sample of 38,432 women who were aged 45 years or older between 1992 and 1995. The researchers collected dietary information and followed the women over a ten year period (on average). During this time, 1,188 of the women developed invasive breast cancer.

The key finding was that, "Consumption of caffeine and caffeinated beverages and foods was not statistically significantly associated with overall risk of breast cancer." The researchers also noted that among women with benign breast disease, there was a non-significant positive association between breast cancer risk and being in the highest fifth (quintile) of caffeine consumption. This subgroup of women also had a positive and significant relationship between breast cancer and being in the highest category of coffee consumption - 4 cups or more each day.

Ishitani and colleagues also found a relationship between consuming caffeine and estrogen receptor-negative and progesterone receptor-negative breast cancer - tumors to which the hormones estrogen and progesterone do not bind. Caffeine consumption was linked to a 68% increased risk of these types of cancer and a 79% increased risk for breast tumors larger than 2 centimeters.

"The mechanisms by which caffeine may affect breast carcinogenesis [cancer development] are complex and remain unclear," conclude the researchers. "In the present investigation, caffeine consumption was associated with increased risk of breast cancers negative for both estrogen receptors and progesterone receptors or larger than 2 centimeters, which have less favorable prognoses. These findings indicate that caffeine consumption may affect breast cancer progression, and such an effect may be independent of the estrogen pathway."

Caffeine Consumption and the Risk of Breast Cancer in a Large Prospective Cohort of Women
Ken Ishitani; Jennifer Lin; JoAnn E. Manson; Julie E. Buring; Shumin M. Zhang
Archives of Internal Medicine (2008); 168[18]: pp. 2022-2031.
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Written by: Peter M Crosta
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