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Coffee consumption may reduce breast cancer risk
  NEW YORK (Reuters Health) - High levels of coffee consumption may reduce the risk of breast cancer among women with BRCA1 gene mutations, according to a multicenter team of investigators.
The results of some animal studies have suggested that coffee consumption may increase the risk of breast cancer, while others have found that coffee may suppress breast tumors, Dr. Steven A. Narod, of the University of Toronto, Ontario, and colleagues report.
In a matched case-control study, the researchers examined the association between coffee consumption and the risk of breast cancer among 1690 high-risk women with BRCA1 or BRCA2 mutations. Included in the study were women from 40 clinical centers in four countries. A self-administered questionnaire was used to assess the average lifetime coffee consumption, and conditional logistic regression analysis was used to estimate odds ratios.
The odds ratios for breast cancer among BRCA mutation carriers who drank no coffee, 1 to 3 cups, 4 to 5 cups, or 6 or more cups of coffee were 1.00, 0.90, 0.75, and 0.31, respectively, (p for trend = 0.02) after adjustment for potential confounders, according to the report in the January issue of the International Journal of Cancer.
When the investigators stratified the women by mutation status, they found a significant protective trend for increasing caffeinated coffee consumption among women with a BRCA1 mutation (p = 0.009). No such trend was found for carriers of a BRCA2 mutation.
The investigators note that coffee is an important source of phytoestrogens, which may have chemoprotective effects.
"The mechanism by which phytoestrogens may beneficially influence the risk of breast cancer has predominantly been attributed to their structural similarity to endogenous estrogens and their ability to bind to estrogen receptors," Dr. Narod and colleagues explain.
"Coffee consumption has been associated with a higher level of circulating sex hormone binding globulin, which decreases the level of bioavailable estrogen."
"It will be of importance to confirm this association in other populations and, if confirmed, to explore the biologic basis for this observation," the researchers conclude.
Int J Cancer 2006;118:103-107.
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